Atlas-of-Neurosurgical-Techniques-Spine-and-Peripheral-Nerves

334
CervicothoracicJunction:AnteriorApproach
Figure44-3
The Synthes cervical spine locking
plate is used for anterior instrumentation
inthe
cervical spine because it is not prebent to match
the lordosis of the spine.
Suggested
Readings
1.
Charles
R. Shunmugam
G. Anterior
approach
to the upper
thoracic
vertebrae.
J Bone Joint Surg Br 1989:71 B:81-84
2.
Fessler
RG. Dietze
DO. Surgical
approaches
to the cervicothoracic
junction.
In: Schmidek
HH. Sweet WHo eds. Operative
Neurosurgical
Techniques:
Indications,
Methods,
and Results. 3M ed. Philadelphia:
WB Saunders;
1995:1875-1886
3.
Hodgson AR. Stock FE. Fang HSY,Ong GB. Anterior
spinal fusion:
the
operative
approach
and pathological
findings
in 412 patients
with
Pott's disease ofthe
spine. Br J Surg 1960;48:172-178
4.
Johnson
RM. Southwick
WOo Surgical
approaches
to the spine. In:
Rothman
RH, Simeone
FA, eds. The Spine. 2nd ed. Philadelphia:
WB
Saunders;
1982:67-187
5.
Sundaresan
N. Shah J. Foley KM. et at. An anterior
surgical approach
to the upper thoracic vertebrae.J
Neurosurg
1984:61 :686-690
6.
Sundaresan
N. Shah J. Feghall: The trans-sternal
approach
to the up-
per thoracic
vertebrae.
AmJ Surg 1984:198:473-477

45
Transthoracic Approach
to the Thoracic Spine
Anthony K. Frempong-Boadu
and Richard G. Fessler
.
Indications
. Contraindications
. Advantages
.
Disadvantages
. Anatomy
ChestWall
Ribs/Spinal Column
. SurgicalTechniques
Approach
PatientPreparationand Positioning
Thetransthoracic approach to the thoracic and upper lum-
barspine is used extensively in the surgical treatment of
thoracic disk disease, spinal deformities,
vertebral
os-
teomyelitis,traumatic burst fracture or fracture dislocation
ofthespinal column, and tumors of the vertebral bodies.! It
isbest used for exposing anterior pathology of the verte-
bralbodies, intervertebral
disks, spinal cord, and nerve
rootsfromT4 to T11.It offers excellent anterior exposure of
thethecal sac, and extensive bilateral anterior decompres-
sionandvertebralbodyresectioncanbe performed(Table
45-1). Only the contralateral
pedicle and posterior ele-
mentsare inaccessible with this approach. Multiple verte-
bralbody levels can be exposed using the transthoracic
approach,and direct reconstruction
of the anterior load-
bearingsupport structures and stabilization with anterior
instrumentation can be accomplished. The thoracolumbar
Incision
Dissection
.
Decompressive
Techniques
Thoracic Diskectomy
Thoracic Vertebrectomy
Closure
.
Complications
.
Conclusions
junction and upper lumbar spine are also exposed using
the transthoracic approach. This is accomplished by de-
taching the diaphragm at its lateral periphery allowing full
exposure of the lower thoracic and upper lumbar verte-
brae.
Transthoracic approaches to the spine were initially de-
veloped for the treatment of Pott's disease in the 1940s.2-4
In 1956 Hodgson and Stock provided the first extensive
description of the use of the transthoracic approach for an-
terior thoracic spinal debridement and fusion in the treat-
ment of spinal tuberculosis.s
Its principal disadvantages are that it exposes patients
to the potential pulmonary morbidity of a thoracotomy,
and it requires a second procedure for decompression of
posterior
pathology and placement
of posterior spinal
instrumentation.
335

..,.
i
336
CervicothoracicJunction: Anterolateral Approach
Table 45-1
Indications for Transthoracic Vertebrectomy and Transthoracic Diskectomy
Transthoracic Vertebrectomy
Anterior compression with significant
osseous involvement and deformity
caused by:
Osteomyelitis
Neoplastic lesions
Metastatic lesions
Primary bone tumors
Burst fractures
Trauma
Pathological
Compression fractures
Trauma
Pathological
Fracture dislocation
Trauma
Transthoracic
Diskectomy
Central calcified thoracic HNP
Diskitis with phlegmon
Anterior release for deformity
correction
HNP,Herniated
nucleus pulposis
.
Indications
. Anatomy
.
Thoracicdisease
.
Spinaldeformity
.
Vertebralosteomyelitis
.
Trauma resulting in burst fracture
.
Traumaresulting in translocation of spinal column
.
Tumorsof the vertebral body
Proper surgical management of thoracic spine lesionsis
based on a thorough
understanding
of the pertinent
anatomy.Theanatomyofthe thoracicspinecontrastswith
that of the cervical and lumbar spine because ofthecom-
plex osseoligamentous
articulation with the thoracicrib
cage. A clear understanding
of the anatomy of the chest
wall, thoracic cavity, relevant vasculature, and neurological
and bony anatomy is essential for performing anteriortho-
racic procedures, thus optimizing the chance to providethe
patient with a safe and functional result.6-8
.
Contraindictions
Chest Wall
.
Pathology above T4
.
Advantages
The anterior approach to the thoracic spine is accomplished
via a posterolateral thoracotomy incision. There aretwo
main muscular layers traversed with this approach.Thefirst
superficial layer is composed of the trapezius and thelatis-
simus dorsi muscles. The accessory nerve innervatesthe
trapezius, and the long thoracic nerve innervates thelatis-
simus dorsi.
The second, deeper muscular layer is composed ofthe
rhomboid muscles and the serratus anterior, whichcontrol
the scapula and shoulder girdle. The dorsal scapulanerve
innervates the rhomboid muscles whereas the longthoracic
nerve innervates the serratus anterior.
The ribs and intercostal spaces form the next layer.Theribs
are enveloped in a periosteum. The intercostal musclelayeris
made up of three individual muscle layers.The superficialex-
ternal intercostal muscle layer,the internal intercostalmuscle
layer, and the innermost intercostal muscle layer.Theneu-
.
Anteriorexposuretothe vertebralbodies,intravertebral
disks, spinal cord, and nerve roots (T4-111 )
.
Disadvantages
.
Increasedpulmonary morbiditycomparedwith thora-
cotomy
.
Requires a second procedure to access the posterior
pathologyand/or to placeposteriorinstrumentation

45
Transthoracic Approach
337
rovascular bundle runs in the costal groove on the inferior as-
pect of each rib and lies between the internal intercostal and
innermost costal muscle layers. The vein runs superior to the
artery and nerve and drains into the azygous system. The in-
tercostal artery is a direct branch off of the descending
aorta.
Thenerve runs medially to its respective foramina. The pleura
isdeep to the intracostal musculature
and is divided into two
layers.The parietal pleura surrounds
the thoracic cavity, and
the visceral pleura envelops the lung.8-11
Ribs/Spinal Column
Thedorsal, ventral, and lateral diameters of the vertebral
bodiesincrease from the cervicothoracic junction to the
thoracolumbarjunction. The physiological kyphosis of the
thoracicspine results from the relatively greater height of
thedorsalvertebral wall compared with the ventral verte-
bralwall.
Thethree-dimensional anatomy of the rib head, trans-
verseprocess, pedicle, neuroforamen, rib articulation with
thevertebral body and disk, and intercostal neurovascular
bundleis complex. Both bony and ligamentous anatomy
providesimportant landmarks for the transthoracic ap-
proach.Each rib articulates with the vertebral column in
threeplacesand is attached to its adjacent intervertebral
FACET FOR
TUBERCLE OF RIB
SUPERIOR
ARTICULAR
FACET FOR
PROCESS
HEAD OF RIB
ANTERIOR
COSTOTRANSVERSE
LIGAMENT
COSTOTRANSVERSE
JOINT
POSTERIOR
COSTOTRANVERSE
LIGAMENT
SPINOUS
PROCESS
ANTERIOR
COSTOTRANSVERSE
UGAMENT
MIDDLE
COSTOTRANSVERSE
lORINTEROSSEOUS
h
UGAMENT)
~~
~- ~-~"
COSTOTRANSVERSE
MEMBRANE
UGAMENT
VERTEBRAL
FORAMEN
Figure 45-1
The costotransverse
ligaments:
lateral view (upper
left); axial view (lower left); and dorsal view (right).
disk space and vertebral body by the radiate ligament ven-
trally and the costovertebral ligaments dorsolaterally. The
ventral costovertebral ligament joins the rostral portion of
the
rib neck to the
caudal base of the
transverse
process.8.12.13The costotransverse ligaments run from the
transverse process of each vertebra to the rib and are
divided into superior, posterior,and inferior costotransverse
ligaments. In addition, the capsular ligaments secure the
neck of the
rib to the transverse
process ventrally
(Fig.45-1). The rib tubercle articulates with the transverse
process of its own vertebral body.The rib head has two ar-
ticulating surfaces. The inferior surface articulates with the
upper costal facet of its own vertebral body,and the supe-
rior surface articulates with the inferior costal facet of the
superior vertebral body. The rib head overliesthe interver-
tebral disk space between its own vertebral body and the
body above (e.g.,the sixth rib overlies the T5-T6disk space)
(Fig.45-2). This remains true until the lower thoracicspine
where the rib head articulates predominantly with the ver-
tebral body of the same level.
Knowledge of the anatomy directly adjacent to the verte-
bral column is also essential to the proper and safe expo-
sure of this region. It is important to accurately identify the
thoracic duct, sympathetic chain, segmental vessels, and
great vessels.
ANTERIOR
COSTo-
TRANSVERSE
LIGAMENT
ANTERIOR
COSTOTRANSVERSE
LIGAMENT
MIDDLE
COSTOTRANSVERSE
LIGAMENT
POSTERIOR
COSTOTRANSVERSE
LIGAMENT
~ UNMNEUROSURGERY
C

338
CervicothoracicJunction: Anterolateral Approach
T6 VERTEBRAL
BODY
COSTOVERTEBRAL
ARTICULATION
@ UNM NEUf'lOSURGERY
(!)
COSTOTRANSVERSE'
ARTICULATION
Figure
45-2
Costovertebral
and
costotransverse
articulations.
The thoracic duct begins as the cisterna chyli at the L1-L2
level in the area of the right crus of the diaphragm. It then
advances up the thoracic spine on the right side of the ante-
rior vertebral column. At approximately the T5 level, it
crosses from right to left, ultimately draining into the junc-
tion ofthe left internal jugular and subclavian veins.
The sympathetic chain is identified on the vertebral col-
umn just anterior to the transverse processes. The greater
splanchnic nerve, which emanates from the sympathetic
chain in the midthoracic spine, runs down the vertebral
column anterior to the sympathetic chain before entering
the abdominalcavity through the diaphragm.
Thesegmental vessels are located at the midpoint of the
vertebral body. They run directly on the vertebral bodies
deep to the thoracic duct and the sympathetic chain. The
vein lies superior to the artery and drains directly into the
azygousvenous system, which runs anterior to the anterior
longitudinal ligament before draining into the vena cava.
The segmental arteries originate from the thoracic aorta and
generally run inferior to the segmental veins (Fig.45-3).
The blood supply to the thoracic spinal cord is unique.
Paired radicular arteries
that course around the spine
supply the thoracic cord. Intramedullary blood supply aug-
ments the radicular blood supply. These vessels feed into
the anterior and posterior spinal arteries, which haveanas-
tomotic zones over the length of the spinal column.Thereis
a relative paucity of intramedullary and radicular arteriesin
the thoracic spine, and this area of the cord is thought tobe
particularly vulnerable to vascular insult. In 60%of patients,
the major radiculomedullary artery of Adamkiewicz arises
on the left side between T9 and L2.14
.
SurgicalTechniques
Approach
In the absence of lateralizing signs, either a left or a right-
sided posterolateral thoracotomy approach can be used to
expose the thoracic spine. Many surgeons advocate the use
of a left-sided approach because of the relative ease ofmo-
bilizing the aorta versus mobilizing the friable vena cavaor
azygous venous system.6.10.15For upper thoracic lesions
(T2-T6),a right-sided posterolateral thoracotomy is gener-
ally preferred because the left side of the upper thoracic
spine is relatively less accessible because of the locationof
the heart, aortic arch, and great vessels. However, for lower
thoracic and thoracolumbar
lesions (T7-L2), a left-sided
thoracotomy is generally preferred because it is technically
easier to mobilize the aorta, and liver retraction is avoided.
Within these generalizations, the side of approach chosen
should allow maximum exposure of the pathology to be
treated.6.10.15
Patient Preparation and Positioning
For lesions in the upper to midthoracic spine (T2-T8)a
double-lumen tube is placed so that the patient can be
ventilated using the dependent lung only, while the upper
lung is deflated and packed off to allow maximal exposure
Intercostal
a.
Figure 45-3

45
TransthoracicApproach
339
ofthelevelofinterest. ForlesionsbelowT8,a double-lu-
mentube is usually not necessary.
Afterinduction of anesthesia, the patient is positioned in
afulllateraldecubitus position with the side to be operated
on in the up position. This places the spine in a 90 degree
orientation to the floor, alIowing for safer decompression
andscrewplacement during instrumentation. The lower leg
iskeptstraight and the upper leg is flexed, facilitating mus-
cleretraction by relaxing the ipsilateral iliopsoas muscle. An
axillaryroll is placed beneath the axilla to prevent brachial
plexusinjury, and a pillow is placed between the legs. The
levelof interest is placed over the break in the operating
table,which is flexed to spread the rib cage, facilitating ex-
posure.Allpressure points are padded and the patient's po-
sitionis maintained using a beanbag or a universal pelvic
positioner.The patient is then secured to the operating
roomtable using heavy tape (Fig. 45-4). Somatosensory
Figure45-4
The patient is placed in the lateral decubitus
position
with the access side up. The axillae and all body prominences
are
padded. An axillary roll is used to protect the dependent
axillae, chest
wall,brachial plexus, and scapula. The patient is taped securely to the
operating table to permit intraoperative
rotation. The positions of the
pathology, portals, scapula. and a potential thoracotomy
incision are
marked on the chest wall. The upper arm is elevated
to move the
scapuladorsally and cephalad, away from the lateral chest wall. A uni-
lateral pneumothorax
is provided by blocking the endotracheal
tube
unilaterally.The nonventilated lung becomes atelectatic,
providing ex-
posure to the spine.
evoked potential
(SSEP)monitoring is used as indicated,
and fluoroscopyor plain x-rays are used to mark the level of
interest
and plan the incision. The surgeon
faces the ante-
rior side of the patient, whereas the assistant
stands
facing
the posterior side of the patient.
Incision
After the patient
is shaved, prepped, and draped in a
through sterile fashion, an incision is made just below the
angle of the scapula and is brought anteriorly toward the
nipple for exposureof upper thoraciclesions.Formid- to
lower-thoracic lesions the incision isgenerallymade overly-
ing the intercostal space or rib one to two levels above the
vertebrallevelof interest.Forthoracolumbarlesionsthein-
cision is typically made over the tenth or eleventh ribs (Fig.
45-5). The incision is carried down to the fascia using the
electrocautery. The latissimus dorsi and the serratus anterior
and posterior muscles are then identified and dividedin line
with the incision using the electrocautery. For upper tho-
racic exposures the trapezius and rhomboid muscles are di-
vided posteriorly and the scopula is retracted dorsal and lat-
eral. The appropriate level is confirmed using fluoroscopyor
plain films, and a subperiosteal dissection is performed, ex-
posing the appropriate rib, with care taken not to violate the
neurovascular bundle underlying the inferior aspect of the
rib. The rib is then disarticulated from the costochondral
junction and cut -3 to 4 cm from the rib head. AFinochietto
retractor is padded and placed and the ribs are spread. A
choice is then made whether to expose the spine via an
extrapleural or an intrapleural approach.
Dissection
Ifan extrapleural approach is performed, a dissection plane
is developed between the endothoracic fascia of the tho-
racic wall and the parietal pleura. The parietal pleura is
bluntly dissected off the inner chest wall and vertebral bod-
ies, directly exposing the radicular vessels, sympathetic
chain, rib head, and vertebral bodies. Anextrapleural proce-
dure avoids entering the pleural cavity,thus eliminating the
need for chest tube placement and reducing pulmonary
morbidity.16It is difficult to avoid pleural tears in elderly or
debilitated patients, or in patients with previous thoracic
surgery.Thenumber of levelsexposedis alsolimitedinan
extrapleural exposure.16
With an intrapleural
approach, the chest is entered
through the rib bed periosteum, the underlying endotho-
racic chest wall fascia, and the parietal pleura. The lung is
retracted, and the spine is observed through the parietal
pleura. Apleural flap is gently elevated to expose the under-
lying structures. After the appropriate vertebral body level
is confirmed using fluoroscopy or plain x-ray,the segmental
vessels are identified and ligated at the midpoint of the ver-
tebral body. The anastomotic vascular arcade in the region
of the proximal neuroforamen should be preserved to avoid
ischemic spinal cord complications.6.14.17
The disk spaces are
identified and the appropriate decompression, reconstruc-
tion, and stabilization are performed depending on the
goals of the operation.

340
Cervicothoracic Junction: Anterolateral Approach
A
Rib8
partially
resected
Parietal pleura /
bluntly dissected
away from ribs,
then remove
rib head
B
Figure 45-5
(A)The incisionis started at the lateral border of the paraspinal musculature and is carried obliquely across the rib -3 inches.
(8) For an extrapleural approach, a short segment of rib is resected. and the plane between the chest wall and the parietal pleura is bluntly
dissected.
Forexposure of the thoracolumbar junction and upper
lumbar spine the skin incision is made in the region of the
tenth or eleventh rib. The incision is carried obliquely and
more ventral depending on the extent of the caudal expo-
sure required. The tenth or eleventh rib is exposed and re-
sected and the chest is entered in a standard fashion. The
costal cartilage of the rib can be split longitudinally, al-
lowing access to the properitoneal fat layer that lies cau-
dal to the diaphragm
and
is continuous
with
the
retroperitoneal
space. The peritoneum
is then cleared
from the undersurface of the diaphragm, avoiding entry
into the peritoneal cavity. The diaphragm is kept under
tension and a circumferential incision is made in the me-
dial portion of the diaphragm along its peripheral attach-
ment to the costal margin, leaving a generous cuff for
later muscle reapproximation. This allows exposure of the
rostral retroperitoneal
space. The spleen, kidneys, and
stomach are retracted medially and caudally using a broad
malleable retractor. The crus of the diaphragm is identi-
fied and cut at its attachment to the anterior longitudinal
ligament at L1and L2.8The anterior surfaces of the verte-
bral bodies of the thoracolumbar junction are then visual-
ized. The intercostal vessels are identified and ligated in
a standard
fashion. The disk spaces are identified and
the appropriate decompression, reconstruction, and stabi-
lization are performed
depending
on the goals of the
operation.
.
DecompressiveTechniques
Thoracic
Diskectomy
It is critical to accurately identify the appropriate interver-
tebral disk space preoperatively when planning a transtho-
racic approach for diskectomy. Along sagittal magneticres-
onance imaging (MRI) scan that includes the thoracic
pathology and either (2 or the sacrum is necessary tocount
accurately.Thismust becorrelatedwith preoperativeplain
radiographs that show the number of rib bearing vertebrae
and the number of lumbar vertebrae. This point cannotbe
overemphasized. Intraoperative identification of the wrong
disk space may otherwise occur.18-20
The side of approach to a herniated thoracic disk isdeter-
mined as already described. Astandard posterolateral tho-
racotomy approach is performed to expose the appropriate
level. It is important to note that the ribs articulate withthe
vertebral bodies at the rostral aspect of the vertebral bodies,
directly overlying the disk space. Therefore, the thoraco-
tomy should be performed through the rib or intercostal
space one level cephalad to the disk space of interest. For
example the T6-T7 disk space will be found directly under-
lying the head of the seventh rib. The disk space level
shouldbeidentifiedusinganintraoperativeradiographthat
should be correlated to preoperative studies before continu-
ing with the procedure.

45
TransthoracicApproach
341
Thepleura is incised longitudinally overlying the appro-
priate disk space and elevated to expose the vertebral
body
aboveand below the disk space of interest.
The head of the
ribis then exposed and excised using either a high-speed
drillor an osteotome. The radial and costovertebral liga-
mentsare then disrupted with a curette to allow excision of
the rib head. The intercostal nerve can be identified and
tracedmedially to identify the neural foramen. AKerrison
rongeuris used to resect the ventral portion of the pedicle
caudalto the appropriate disk space. This allows visualiza-
tionofthe thecal sac and will often provide direct visualiza-
tionofthe herniated disk.
Thediskspace is then incisedwith a knifeblade or os-
teotomeand removed anterior to the herniation using large
curettesand rongeurs (Fig.45-6). Ahigh-speed drill is then
usedtowiden the disk space posteriorly until a thin cortical
"eggshell"remains, thus creating a trough anterior to the
spinalcanal and the disk herniation. This allows the sur-
geonto pull the disk herniation and the thin rim of remain-
ingcorticalbone anteriorly away from the spinal cord using
Epsteincurettes into the trough that was previously cre-
ated.17,18.20.21
The posterior longitudinal ligament should also be re-
sected using small Kerrison rongeurs.
The entire
width
of
thespinal canal should be decompressed.
If uncertainty
ex-
istsabout the adequacy
of decompression,
a marker can be
placedin the area of decompression and an x-ray taken to
check the extent of decompression.18.19.21
ThoracicVertebrectomy
Thoracicvertebrectomy is performed to relieve anterior
compressionof the spinal canal from tumor, infection, or
fracture.The side of the approach is dependent on the loca-
tionand anatomy of the spinal compression. A standard
posterolateral thoracotomy
approach
with a rib resection
is
Figure 45-6
The pedicle is removed to expose the dura. A cavity is
drilledin the vertebral
body and disk space to provide
room to insert the
toolsto remove the herniated disk.
performed. The resected rib is typically
the rib one to two
levels above the vertebral level of interest in the mid- to
lower thoracic regions, and one above in the upper thoracic
region.
With the chest exposedand the lung retracted, the pleura
is incised longitudinally
with
electrocautery,
with
care
taken not to violate the underlying segmental vessels. The
appropriate
level is identified using fluoroscopy or plain
films. The segmental vesselsof the vertebral body to be re-
sected aswell as one vertebral body proximal and distal are
then identified and controlled asalready described.
The boundaries of the vertebral canal must be clearly de-
lineated before continuing with vertebrectomy. This avoids
inadvertant entry into the canal and facilitates ideal place-
ment of instrumentation
if necessary. The end plates and
disk spaces above and below the level of interest must be
clearly identified. Disarticulating
the rib head at the levels
of interest using a high-speed drill or rongeurs identifies
the pedicles. Once the disk spaces above and below the
level of interest and the pedicles have been exposed; the
dorsolateral edge of the vertebral body is identified using a
no.4 Penfield dissector. With the canal identified, the sur-
geon may safely proceed with the vertebrectomy. The disk
spaces above and below the level of interest are incised
with a knife blade or osteotome and removed using large
curettes and rongeurs. The vertebrectomy is performed us-
ing rongeurs and a large high-speed cutting bur, creating a
trough in the lateral aspect of the vertebral body and then
enlarging the trough to the far lateral side and posteriorly to
the cortex. A high-speed drill is used to thin the posterior
and far lateral cortex to an eggshell width. Curettes are then
used to tease the thinned posterior cortex anteriorly off the
thecal sac(Fig.45-7). The posterior longitudinal ligament is
then removed using curettes
and Kerrison rongeurs. To en-
sure complete decompression, the pedicle on the deep side
of the vertebral
body should be palpated.
Bleeding during
the vertebrectomy
is controlled
using bone wax, Gelfoam,
and efficient resection of cancellous bone back to the rela-
tively avascular
cortical
bone.
Control
epidural
bleeding
with Gelfoam and bipolar cautery. The anterior
longitudinal
Figure 45-7
The posterior cortex of the vertebrae, the posterior lon-
gitudinalligament,
and the pathology compressing the spinal cord are
resected.
The bone and ligament are dissected
away from the spinal
cord into the cavity in the vertebral body.

342
Cervicothoracic Junction: Anterolateral Approach
ligament and the far lateral cortex are kept intact as much
as possible to provide stability and a means for keeping
anterior and deep lateral checks on the reconstruction pro-
cedure.ls
Closure
Ifthe diaphragm was opened. great care must be taken to
accurately reattach it to its costal margin. The crus should
be reattached to the anterior longitudinal ligament and any
tears in the peritoneum should be repaired. The pleura may
be mobilized by bluntly dissecting it laterally off the tho-
racic wall. The parietal pleura should be closed if possible,
overlying the vertebral column and any hardware. Ano. 28
French chest tube is placed and positioned at the apex of
the lung and tunneled out through the subcutaneous tissue
to a separate incision inferior to the thoracotomy incision.
The lung is then reinflated under direct visualization and
the ribs approximated using a rib approximator. The ribs are
compressed and reapproximated with heavy absorbable su-
ture. The rib bed is tightly reapproximated to reestablish a
pleural seal. The intercostal musculature is closed using a
running suture. The serratus anterior and the rhomboid
muscle are then closed with running suture. The superfi-
cial muscle layer consisting of the latissimus dorsi and
trapezius muscles is also closed with a running suture. The
subcutaneous
tissue is closed with simple interrupted
suture and the skin is closed using a subcuticular suture or
skin staples. The chest tube is secured to the skin in a stan-
dard fashion and placed to suction.
The chest tube is removed when drainage is less than 50
mLper 8 hours. A chest film should be obtained -6 hours
References
1.
Cahill DW. Love LC, Rechtine
GR. Pyogenic
osteomyelitis
of the spine
in the elderly [see comments].J
Neurosurg
1991 ;74:878-886
2.
Hodgson AR,Stock FE. Anterior
spine fusion for the treatment
of tu-
berculosis
of the spine:
the operative
findings
and results
of treat-
ment in the first 100 cases. J Bone Joint Surg Am 1960;42A:295-31O
3.
Hodgson AR,Wong SK.A description
of a technique
and evaluation
of
results in anterior
spinal fusion for deranged
intervertebral
disk and
spondylolisthesis.
Clin Orthop
1968;56: 133-162
4.
RichardsonJD,
Campbell DL,Grover FL,et at. Transthoracic
approach
for Pott's disease. Ann Thorac Surg 1976;21 :552-556
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Hodgson
AR,
Stock
FE.
Anterior
spinal
fusion.
Br
J
Surg
1956;46:266-275
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Burrington
JD, Brown C. Wayne ER, Odom J. Anterior
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to the
thoracolumbar
spine:
technical
considerations.
Arch
Surg
1976;111 :456-463
7.
Ebraheim
NA, Xu R,Ahmad M, Yeasting RA.Anatomic
considerations
of anterior
instrumentation
of the
thoracic
spine.
Am J Orthop
1997;26:419-424
8.
Watkins
RG. Surgical Approaches
to the Spine. New York: Springer-
Verlag; 1983
9.
Cook
WA.
Transthoracic
vertebral
surgery.
Ann
Thorac
Surg
1971 ;12:54-68
10.
McElvein
RB, Nasca RJ,Dunham
WK, Zorn GLJr. Transthoracic
expo-
sure for anterior
spinal
surgery.
Ann Thorac Surg 1988;45:278-283
11.
Smith
TK, Stallone
RJ, Yee JM. The thoracic
surgeon
and
anterior
spinal surgery. J Thorac Cardiovasc Surg 1979;77:925-928
12.
Leventhal
M. Spinal anatomy
and surgical
approaches.
In: Crenshaw
R, ed.
Campbell's
Operative
Orthopaedics.
St.
Louis:
Mosby;
1992:3493-3516
after the chest tube is removed to rule out a delayed pneu-
mothorax.
.
Complications
Pulmonarycomplicationsaremostfrequentwithtranstho-
racic approaches. Atelectasis, pneumonia, pleural effusions,
and chest wall discomfort are all possible with this approach.
Rapid mobilization and early postoperative involvementof
physiatrists and physical therapists are desirable in these pa-
tients to prevent pulmonary complications and diminishthe
risks ofpostoperative thromboembolic complications.
Vascular injuries, nerve root injuries, Horner's syndrome,
pleural effusion from chylothorax. bronchopulmonary fis-
tula, and prolonged chest wall pain (postthoracotomy pain
syndromes) have all been reported with transthoracic ap-
proaches
to the spineI7.22.23
. Conclusions
Decision making regarding approaches to the thoracic spine
depends upon the location of the pathology, the need for
thecal sac decompression, and the presence of spinal defor-
mity. The transthoracic approach offers a safe and effective
means of treating anterior compressive lesions of the tho-
racic spine caused by thoracic disk herniations, vertebral
body osteomyelitis/diskitis, metastases, burst fractures,and
kyphoscoliosis. It allows for direct neural decompression,
placement of interbody grafts under compression. and the
ability to correct sagittal and coronal plane deformities.
13.
McCormack
BM. Benzel EC, Adams MS. et at. Anatomy
ofthe
thoracic
pedicle. Neurosurgery
1995;37:303-308
14.
Lu J, Ebraheim
NA, Biyani A, et at. Vulnerability
of great
medullary
artery. Spine 1996;21: 1852-1855
15.
Lobosky JM, Hitchon
PW, McDonnell
DE. Transthoracic
anterolateral
decompression
for
thoracic
spinal
lesions.
Neurosurgery
1984;14:26-30
16.
McCormick
Pc. Retropleural
approach
to the
thoracic
and thora-
columbar
spine. Neurosurgery
1995;37:908-914
17.
Sekhar
LN, Jannetta
PJ. Thoracic
disk
herniation:
operative
ap-
proaches
and results. Neurosurgery
1983;12:303-305
18.
Currier
BL,Eismont
FJ, Green BA.Transthoracic
disk excision and fu-
sion for herniated
thoracic disks. Spine 1994;19:323-328
19.
Perot PLJr. Munro DD. Transthoracic
removal
of midline
thoracic disk
protrusions
causing
spinal
cord
compression.
J
Neurosurg
1969;31 :452-458
20.
RansohoffJ.
Spencer
F,Siew F, Gage LJr. Transthoracic
removal of tho-
racic disk: report of three cases.J
Neurosurg
1969;31 :459-461
21.
Bohlman
HH, Zdeblick
TA. Anterior
excision
of herniated
thoracic
disks. J Bone Joint Surg Am 1988;70: 1038-1047
22.
Faciszewski
T, Winter
RB, Lonstein JE, et at. The surgical
and medical
peri operative
complications
of anterior
spinal
fusion surgery
in the
thoracic
and lumbar
spine
in adults:
a review
of 1223 procedures.
Spine 1995;20: 1592-1599
23.
Fessler RG, Sturgill M. Review: complications
of surgery
for thoracic
disk disease. Surg NeuroI1998;49:609-618

46
LateralParascapularExtrapleural Exposure
ofthe Upper Thoracic Spine
RichardG. Fessler
. Indications
. Contraindications
. Advantages
. Disadvantages
. Objective
. SurgicalTechnique
Anesthesiaand Positioning
Incisionand Musculocutaneous
Flap
Openingthe Thoracic Cage
lateralVertebrae and Thecal Sac Exposure
Diskectomy
Vertebrectomy
VertebralReconstruction
PosteriorInstrumentation
Closure
Obtainingsurgical access to the anterior vertebral ele-
mentsofthe upper thoracic vertebrae (T1-T6) presents a
uniqueanatomical challenge.
The thoracic
cage, which
narrowssignificantly as it approaches
the thoracic
inlet,
hasanintimateassociation between the vertebral column
andthe superior mediastinal
structures.
The supraclavicu-
lar.transmanubrial, and transthoracic
approaches
to this
regiongiveexcellent access to limited
parts of the upper
thoracicspine,but none provides access to all of the upper
thoracicvertebrae.Ananatomically guided procedure, the
lateralparascapular extrapleural approach to the upper
thoracicspineallows excellent exposure of all upper tho-
racicvertebraeforneural decompression, corpectomy, ver-
tebralreconstruction,and simultaneous
posterior spinal
fixation.
. Indications
. Vertebralneoplasm
. Vertebralfracture
.
Osteomyelitis
.
Diskherniation
. Diskitis
.
Ventral intradural extramedullary tumor
.
Contraindications
.
life expectancy less than 3 to 6 months
.
Medical illness that would preclude major surgery
. Advantages
.
Completeaccess of all thoracicvertebrae and ventral
spinalcordto inferiorC7
.
Abilityto performanteriorand posteriorreconstruction
in a singleapproachdoesnot enter pleuralcavity
343

344
CervicothoracicJunction: Posterolateral Approach
.
Disadvantages
Incision and Musculocutaneous
Flap
.
Prolongedexposure
.
Significantblood loss
. Objective
Thegoal of this procedure is to obtain direct visual and
manualaccessto the ventralspinalcordandanteriorverte-
bralelements.
. SurgicalTechnique
Anesthesiaand Positioning
General anesthesia is used with a double-lumen endotra-
cheal tube or a single-lumen tube using a high-frequency
positive pressure ventilation technique. Ifa double-lumen
technique is chosen, selective lung collapse can be used to
aid visualization. If a single-Iuman technique is chosen,
high-frequency ventilation results in less excursion of the
lung into the operative field. The patient is positioned
prone on chest rolls with the arms tucked to the sides. The
chest role ipsalateral to the side of approach must be posi-
tioned medially to allow the shoulder and scapula to fall
ventrolaterally, out of the operative field, when the trapez-
ius and rhomboid muscles are released from the spinous
processes.
Inferior scapular
angle (T-7)
Figure 46-1
The lateral parascapularincisionisperformed along the
midline and then angled off at the levelof pathology.
The incision extends from three to four levels above the le-
sion to three to four levels below it. However, because ofthe
relative tethering
effect of the trapezius
and levator scapu-
lar muscles, a lesion located at T1 or T2will requireaninci-
siom that extends all the way up to approximatelyC3or(4.
Helpful landmarks upon which to base the incisioninclude
the spinous process of C7, the superior scapular angle (B),
and the inferior scapular tip (T7) (Fig. 46-1). Notethat in
the prone position, prior to takedown of the trapeziusand
rhomboid musculature, the scapula coversthe lateralhalfof
the posterior rib cage. This position makes mobilizationof
the trapezius and rhomboid musculature imperativetoex-
posure of the upper thoracic spine. This incisionismadeto
the deep fascia with minimal subcutaneous undermining.
The trapizius, rhomboid, and splenius musclesarethen
dissected
off the spinous
processes
in the subperiosteal
plane, while the muscle layers are identified on edgeas
they are stripped
(Figs. 46-2, 46-3). The interspinous liga-
ments
are left intact. A plane of loose areolar tissue islo-
cated between
these shoulder
muscles
and the musclesof
the back proper, which permits blunt dissection with the
surgeon's fingers. The trapezius, rhomboid, serratus poste-
rior superior, splenius capitis, and splenius cervicismuscles
are taken down as a group for lateral retraction. The inferior
fibers of the trapezius muscle must be transected to reflect
this flap, and care is taken
to leave a cuff of identifiable
muscle for reapproximation at wound closure (Fig.46-4).
The medial border of the scapula falls laterally with mobi-
lization of the trapezius and rhomboid muscles, providing
an excellent exposure of the upper dorsal rib cageanddor-
sal vertebral elements.
Figure 46-2
Artist'sdepiction of vital structures includingdescend-
ing aorta inrespect to the spine.

46
Lateral Parascapular Extrapleural Exposure
345
Serratus
anterior
Subscapularis
Scapula
Infraspinatus
Figure46-4
The trapezius muscle is reflected laterally to expose the
deeper musculature.
Thenext group of muscles encountered are the deep, or
intrinsic, muscles (Figs. 46-2, 46-5). The erector spinae
musclesare dissected from the spinous processes, lami-
nae,and transverse processes as a single muscular mass
(Fig.46-6). The insertions of the iliocostalis thoracis mus-
clesare also taken down. Control of the musculature
in
thisway exposes all vertebral elements from the tip of the
spinousprocesses to the tip of the transverse processes,
aswell as the costotransverse
ligaments, the joints, and
theribs.
Opening the Thoracic Cage
Thethoraciccageisopened dorsallyby removingtwo or three
ribsfrom their costotransverse and costovertebral articula-
tionstothe posterior bend ofeach rib.The ribs to be removed
arechosentogivemaximum exposureof the pathology.
Toexpose a vertebral body, the corresponding rib and the
ribbelow must be removed (thus, to expose n,
the third
and fourth ribs must be removed) (Figs. 46-7, 46-8). To
allowadequate working room a third rib can be removed.
The intercostal muscles and neurovascular bundles are
strippedsubperiosteally off the ribs (Fig.46-9). The costo-
tranverseand costovertebral ligaments are incised using a
combinationof scalpel. scissors, and periosteal elevators to
Figure 46-3
Cross-sectional drawing of T4 level
demonstrating vertebrae and relationshipto paraspinal
musculature.
.I
I
Figure 46-5
Deep intrinsic musculature of the paraspinal region.
free the rib head and neck. The dorsal rib iscut as far later-
ally as possible, generally just lateral to the posterior bend.
With the cut end of the rib protected the rib and rib head
can be worked free. After further dissection of the costo-
transverse and costovertebral ligaments. the remaining
small amount of radiate ligament can be bluntly avulsed to
remove the rib and rib head in toto. The resected rib can be
set aside in antibiotic solution for use as fusion material.

346
CervicothoracicJunction:PosterolateralApproach
Figure 46-6
Erectorspinae musclesare dissected fromthe spinous
processes laminae and transverse processes as a singularmuscular
mass.
"Inf. costal facet
. Sup.costotransverselig.
Rib
___Synovial
joint
(costovertebrel)
Sup. costotransverseJig.
Figure 46-7
The posterior thoracic spine and the bonyand
ligamentous anatomy.
Spinous process
Transverse process
Costotransverse joint
Lat. costotransverse lig.
Head
Figure 46-8
Cross-sectional
depiction oftho.
racic vertebrae and rib articulation.

46
LateralParascapularExtrapleuralExposure
347
Figure46-9
The neurovascular
bundle
and intercostal
muscles are
dissectedsubperiostally
from the ribs.
Theisolated strip of musculature will contain the inter-
costalnerve, artery, and vein. The intercostal neurovascu-
larbundles are dissected free, and the intercostal muscles
areremoved.The intercostal veins are sacrificed, and the
intercostalarteries are ligated and transected. The inter-
costalnerves can be transected
and tagged for dural
retraction,if necessary, for exposure of the lateral verte-
bralbody.
Lateral Vertebrae and Thecal Sac Exposure
With blunt dissection, the pleura can be separated from the
neurovascular bundle. Following the intercostal nerve me-
dially enables identification of the neural foramen. Within
the foramen, the dorsal root ganglion can be identified
along with the gray and white rami communicantes, which
course ventrally to the sympathetic chain and ganglia (Fig.
46-10). The rami communicantes are transected and the
segmental vasculature is sacrificed.Atthis level of the spine
the intercostal arteries stretch obliquely from caudal to
cephalad across the vertebral elements. C7and T1 nerves
cannot be sacrificed without causing severe neurological
deficit in hand function. Therefore, it is occasionallyneces-
sary to work around the inferior portion of the brachial
plexus in exposures extending up to C7.
After identification of the neural foramen the posterolat-
eral thecal sac is exposed by removal of the transverse
processes,lamina,and pedicleswith a high-speeddrillor
Kerrisonpunch or both.
Diskectomy
Once the neuroforamen is identified and expanded, the pos-
terolateral aspect of the disk will become apparent immedi-
ately ventral to the lateral thecal sac.Hemostasisover the disk
space isachievedwith bipolarcautery.Thedisk space canthen
be incisedusinga no. 15blade scalpel.Diskectomycan be per-
formed using standard, long-handled curettes and pituitary
rongeurs.Accessto the disk space can be enhanced by drilling
the posterolateral portions ofthe end plate to extend the disk
exposure. If only diskectomy is being performed, the plane
between the dural sac and posterior anulus can be identified,
and the anulus can be incisedand safelyremoved under direct
vision.Ifvertebrectomy isto followthe diskectomy,the poste-
rior longitudinal ligament is left in place to further protect the
dura, and attention is next turned to vertebrectomy after
aggressiveand thorough diskectomyiscompleted.
Figure 46-1 0
Thedorsal root ganglion and the gray and
white rami communicantes maybe identified with further
dissection.

348
CervicothoracicJunction: Posterolateral Approach
Vertebrectomy
The lung is collapsed or retracted out of the operative field
using a moist lap and malleable retractors. Vertebrectomy is
then performed using a combination of high-speed drilling
and blunt dissection with curettes and Kerrison punches
(Fig.46-11). The anterior and, if possible, the posterior lon-
gitudinalligaments are preserved. These serve both as pro-
tective barriers for neural and mediastinal structures and as
borders for reconstruction.
Vertebral Reconstruction
Vertebral reconstruction will vary depending upon the spe-
cific operation performed. Fig. 46-12 demonstrates
one
possible technique frequently utilized for reconstruction
followingvertebrectomy for metastatic cancer. In this tech-
nique, entry points are drilled into the end plates of the
superior and inferior end plates of the adjacent vertebral
bodies through which Steinmann pins are introduced and
firmly anchored into the cancellous bone of these bodies.
Further strength can be achieved by anchoring the Stein-
mann pin on the distal end plate of each adjacent vertebral
body.The angled "hook" ends of the pins are then interwo-
ven and the space filled with methyl methacrylate. Care
should be taken during the hardening
of the methyl
methacrylate to protect the spinal cord from compression
resulting from expansion of the methyl. In addition, irriga-
tion should be maintained until the construct is totally hard
to prevent heat transfer to the spinal cord. Reconstruction
for traumatic fracture should be performed with auto- or
allograft bone for permanent fusion of the affected verte-
brallevels.
Posterior Instrumentation
Appropriate posterior spinal fixation is performed usinga
fixed, semirigid rectangular system, which allowsbothaxial
and transverse corrective forces.This is generallyextended
from three segments above to two segments belowthe
margins of the vertebrectomy. An autologous iliac crest
bone graft is used for posterior spinal fusion (Fig.46-13).
Closure
Prior to wound closure the operative fieldisfilledwithsaline
to check for evidence of an air leak. Ifan air leak is present,a
small (22 or 24 French) chest tube should be placed and
brought out percutaneously
in a posterolateral positionbelow
the incision. The wound
is then
copiously
irrigated with
antibiotic solution and inspected for any bleeding. Twodrains
(no. 5 Hemovac or 10 mm Jackson Pratt) are placed. Oneis
placed alongside the vertebral reconstruction and broughtout
percutaneously
below the incision posterolaterally. Theother
is placed adjacent to the posterior spinal fixation and brought
out percutaneously
below the incision near the midline.
A layered
closure
is performed.
The paraspinal muscle
mass is returned
to its anatomical
position, and the thora.
columbar
and deep cervical
fascia are reapproximated to
the midline. The respective muscle layers from each sideare
reapproximated
to the midline, and the superficial anddeep
fascial layers are replaced
in separate
layers, taking careto
obliterate
potential
dead spaces between
layers. The skinis
stapled
and an occlusive
dressing
applied.
The patient is
kept intubated
overnight
to avoid respiratory
compromise
from
soft
tissue
swelling,
and
receives
continuous
neurovascular
monitoring
in the intensive care unit.
Figure 46-11
Avertebrectomy
is performed
with the use
of a high-speed
drill and Kerrison
punches.

....
46
lateral ParascapularExtrapleuralExposure
349
Figure 46-12
A Steinman pin is placed within the
vertebrectomy
site and
methly
methacrylate
is
shaped in the intervening space.
Figure46-13
laminar hooks, pedicle hooks, and transverse
process hooks can be used to supplement the posteriorinstru-
mentation construct.

Section IV
Thoracicand Thoracolumbar Spine
A.Pathologyofthe Thoracicand
ThoracolumbarSpine
. 47. Congenital Abnormalities of the
Thoracicand Thoracolumbar Spine
. 48. DiskDisease of the Thoracic and
Thoracolumbar Spine
. 49. Tumorsof the Thoracolumbar
Spine
. 50. Traumaof the Thoracic and
Thoracolumbar Spine
B.Antero/Anterolateral
Approach
. 51. LateralTransthoracic Approach to
the Spine
. 52. Thoracoabdominal Approach and
Closure
. 53. Retroperitoneal Approach and
Closure
. 54.ThoracicSympathectomy
. 55.Transthoracic Diskectomy
. 56.Transthoracic Vertebrectomy
. 57.Anterolateral Graft and Plate
Reconstruction
C.Posterolateral Approach
. 58.Costotransversectomy
D. Posterior Approach
.
59. Thoracic Laminectomy
.
60. Thoracic Laminoplasty
.
61. Thoracic Epidural Abscess
. 62. Thoracic Extension Osteotomy
.
63. Diagnosis and Management of
Thoracic Disk Herniation and the
Transpedicular Decompression for
Thoracic Disk Herniation
.
64. SpinalArteriovenous Malformations
.
65. Intradural Extramedullary Tumor
Resection in the Thoracic Spine
.
66. Open Anterolateral Cordotomy
.
67. Commissural Myelotomy
.
68. The DREZOperation
.
69. The Caudalis DREZ
.
70. Syringopleural Shunting
.
71. Syringosubarachnoid
Shunting
.
72. Syringoperitoneal Shunting
.
73. Posterior Approach and InSitu
Fusion of the Thoracic Spine
.
74. Pedicle Screw Instrumentation
of
the Thoracic Spine

47
Congenital Abnormalities of the Thoracic
andThoracolumbar Spine
Michael J.Rauzzino,
Christopher I. Shaffrey,
RussP.Nockels,
Mark Abel,
and
RichardEllenbogen
. Epidemiology
. RadiologicalEvaluation
. Embryology
. SpinalDysraphism
. SpinaBifidaAperta (Myelomeningocele)
. Meningoceles
. OccultSpinalDysraphism
. NeurentericCysts
. Lipomyelomeningocele
. Lipomas
. Diastematomyelia(Split Cord Malformations)
. Dermoids,Epidermoids, and Dermal Sinus Tracts
. TetheredCordSyndrome (Tight Filum Terminale)
. CongenitalAnomalies of Vertebral
Bodies
Congenital Scoliosis
. Errorsof Segmentation
Developmental
disordersof the human thoracic spine repre-
sentarangeofconditionsthat have in common some form of
disorderedembryogenesis.Isolated congenital disorders of
thethoracicor thoracolumbar
spine may not be readily ap-
parentatbirth,presenting instead with either deformity or
neurologicaldeficit during early childhood
or adolescence,
whichare times of accelerated vertebral column growth.
Otherconditions,such as spina bifida aperta, are readily ap-
parentatbirthand associated with other syndromes such as
theChiariIImalformation. This chapter outlines the epi-
.
Errorsof Formation
.
Congenital Kyphosis
.
Congenital Lordosis
.
Segmental Spinal Dysgenesis
.
Dysplastic (Congenital) Spondylolisthesis
.
Klippel-Feil Syndrome
.
Intraspinal Cysts
.
Intradural Spinal Cysts
.
Extradural Spinal Cysts
.
Extradural Meningeal Cysts
.
Tarlov's Perineural Cysts
.
Extradural Arachnoid Cysts
.
Lateral or Anterior Thoracic Meningoceles
.
Hydrosyringomyelia
.
Terminal Syringohydromyelia
.
Conclusion
demiology ofthese disorders, discusses the basicembryology
of the thoracic spine, and describes the clinicalfeatures and
treatment of some of the more common congenital abnor-
malities ofthe thoracic and thoracolumbar spine.
.
Epidemiology
Congenital spinal anomalies are usually seen as sporadic
isolated cases with a risk of transmission of less than 1%.1-3
To date there have been no studies to determine a true
353

354
Thoracic and Thoracolumbar
Spine: Pathology of the Thoracic and Thoracolumbar
Spine
population risk. In a study of 1250 patients, Winter et al
found only 13 had a positive family history.2In another study
of 337 patients with congenital spinal deformities, Wynne-
Daviesfound that if the patient had a single focaldefect such
as a hemivertebra there was no increased incidence in sib-
lings or risk of transmission to the patient's offspring.4If,
however,there were multiple-level complex vertebral anom-
alies the risk of transmission to subsequent offspring rose to
5 to 10%.Hereditary congenital scoliosis as part of a syn-
drome such as spondylocostaldysplasia has been reported by
several authors.5-7 Certain conditions such as spinal dys-
raphism have a distinct epidemiology all their own, with an
incidence of 0.1 to 0.2%in North America and a lO-fold in-
creased incidence to 2.5%for subsequent offspringin affected
families.sThere is also an increased risk of subsequent neural
tube defects in children of sisters and daughters of the
mother who has a child with myelodysplasia. Current re-
search has focused on the chromosomal abnormalities asso-
ciated with congenital spinal deformities.Apossiblelocusfor
hemi-vertebrae formation has recently been located on the
short arm of chromosome 17.9Another study noted that a
deletion of a portion of chromosome 18 is associated with
multiple vertebral segmentation defects.1OAn argument
against genetic transmission, however, is that studies of
twins have usually shown that if one twin has the anomaly,
the other does not, even when the twins are identical.5
Disorders of other organ systems can accompany the
spinal deformity. The single most common organ system in-
volved in association with vertebral anomalies is the urolog-
ical system with an association of 20 to 25%.nIn a study by
Bealset al of218patients with vertebral malformations (ex-
cluding myelodysplasia), 43 patients had renal system ab-
normalities, with the most common defect being an absent
or hypoplastic kidney.12Cardiacabnormalities were seen in
nearly 10%of patients with the most common defects, in-
cluding VSD,ASD,dextrocardia, or Fallot's tetralogy. Pul-
monary involvement was seen in 14 patients and the most.
common defect was tracheoesophageal fistula in association
with VATERsyndrome (V= vertebral,A= anal atresia,T =
tracheoesophageal fistula, E = esophageal atresia, R= renal
or radial ray). Cranialnerve deficits were seen in 10%ofpa-
tients and most commonly involve the sixth, seventh, or
eighth cranial nerves.These nerve palsies were often seen in
association with hemifacial microsomia and Goldenhar's
syndrome
(vertebral anomaly, epibulbar dermoids, and
preauricular appendages). Interestingly, type or magnitude
ofthe vertebral anomaly had no association with the occur-
rence or frequency of any related abnormality. Single hemi-
vertebrae carried the same risk for additional abnormalities
as did multiple spine anomalies. Intraspinal abnormalities
such as diastematomyelia and tethering of the cord occur 5
to 35%of the time and maybe signaled by posterior midline
skin lesions (such as hairy patches or deep dimples), asym-
metric foot deformities (cavus or flat feet), or muscle weak-
ness or spasticity. All these systems should be thoroughly
examined when a congenital spinal deformity is discovered.
Renal ultrasound, cardiac consultation, and magnetic reso-
nance imaging (MRI)of the entire brain stem and spinal cord
are essential to a thorough evaluation. The uncovered organ
system defect may be more significant to the patient's well-
being than the spinal deformity.13.14
.
Radiological Evaluation
Allpatients with spinal deformities require imagingstudies
to determine the type and locationofthe vertebralanom-
aly, the presence of compensatory curves, the flexibilityof
the curves, the size of the spinal canal, and the statusofthe
underlying nervous system elements. This informationis
essential to help predict the natural history ofthe deformity
and, if surgeryis indicated,to decide the optimalsurgical
approach.
Radiographs of the entire spine, including frontaland
sagittal views, should be done standing to assesstrunkbal-
ance and the stable zone. Serial radiographic measure-
ments, performed over the same vertebral levelsandshow-
ing a 5 degree increase, have classically been the criteriafor
establishing progression. Side bending and traction views
are used to assess the flexibility of the scoliotic deformity
prior to surgical correction. Polycycloidal tomographycan
be used to better characterize the size, shape, andposition
of the vertebral anomaly.15Recently,computer softwarehas
been developed that renders three-dimensional images
from computed tomography (CT) scan data to assessthe
canal size and shape. The location of a hemi-vertebra inthe
transverse plane, the length of an unsegmented bar,thesta-
tus of adjacent disk space, and the presence or absenceof
posterior elements can be determined
with these tech-
niques. MRIof the entire brain stem and cord has essen-
tially replaced myelography as a mandatory part ofevaluat-
ing congenital
spinal deformities
for the presenceof
intraspinal anomalies, cord impingement, and the relation-
ship of neural elements to the deformity.
.
Embryology
The development of the human spine begins with thede-
velopment of the primitive streak on day 15 of embryonic
life.The embryo at this point is bilaminar with the epiblast
(ectoderm) and hypoblast (endoderm). Adepressiondevel-
ops in the primitive streak forming the primitive groove.
Epiblast cells invade the primitive groove and migratebe-
tween the layers of the epiblast and the hypoblast toform
the embryonic mesoderm, making the embryo a trilayered
structure. The term gastrulationis used to describethis
transformation of a bilayered embryo to a trilayeredem-
bryo. A group of genes that encode a zinc finger protein
have been identified and found to be necessary forappro-
priate mesenchymal cell migration
from the primitive
streak,and abnormalitiesinthese genesmayinterferewith
the process of formation of the mesoderm during gastrula-
tion and with emigration of the neural crest from theneural
tube.16Many congenital disorders of the spine involvemal-
formations of tissues derived from all three embryological
layers. This leads one to postulate that many congenital
spinal disorders arise from defects in gastrulation, anem-
bryological period when all three embryological layersare
available to the same insult. The notochord is formedinthe
midline from the migrating mesodermal cells. Thenoto-
chord induces the overlying ectoderm to form the primitive
neural plate. Primary neurulation involves the formation

andunfoldingof the neural plate to form the neural tube
thateventuallybecomes the spinal cord down to the level
ofthe lumbosacral junction.
The neural
tube is generally
formedby day 21 and then separates
itself from the overly-
ingectoderm,which then fuses to become continuous
over
thedorsal aspect of the embryo. The process of secondary
neurulation results in the development of the spinal cord
segmentsbelow the lumbosacral junction
and occurs days
28to48 after ovulation when neural crest cells migrate into
thedorsal midlineand form a tubular structure that joins
withthedistalend of the spinal cord developing from the
primaryneurulationprocess.
Theprecursors of the vertebral column are the somites,
whichform from thickened paraxial mesoderm lateral to
thedeveloping neural tube. They develop in pairs in a ros-
traltocaudalfashion.Initially,four occipital. eight cervical.
12thoracic, fivelumbar, five sacral. and eight to 10 coc-
cygealpairsof somitesare formed from which the last five
tosevencoccygeal pairs regress. Asthe somites proliferate.
distinctcell massesdevelop.The lateral portion becomes a
dermatomethat is destined to form the skin and subcuta-
neoustissue.Themedialportion is divided into a dorsal and
ventralportion.Thedorsal aspect of the medial somite be-
comesthe myotome that is the precursor to the striated
muscle.The ventral portion of the medial somite becomes
thesclerotome.which develops into the bony and cartilagi-
nousportion of the spinal column. The somites have re-
gionalspecificity early in development. Ifa thoracic somite
istransposedtothe cervicalregion, a vertebra resembling a
thoracicvertebra with extrathoracic ribs will result.
Byday35thesclerotomecells have surrounded the noto-
chordandneural tube forminga mesenchymal analogue of
thevertebraethat will subsequently undergo sequential
overlappingstepsof chondrificationand ossification. Differ-
entiationofthe part of the sclerotome destined to become
thevertebralbody is under the control of the notochord.
whereasthose cells destined to become the neural arch are
underthe control of the neural crest.17Thus, developmental
abnormalitiesthat occur early in gestation may indepen-
dentlyalter either the vertebral body or the vertebral arch.
Suchdifferencesin the timing of anterior/posteriorverte-
braldevelopmentcan result in malformations
such as
hemi-vertebraeor congenital bar-unilateral
arch fusion.
Theformation of the individualvertebral body is believed to
betheresultof the rostral half of one somite migrating to
jointhecaudalhalf of the adjacent somite. This is the the-
oryofresegmentationfirst proposed by Remark.It explains
the anatomical position of the intersegmental
arteries
crossingthe vertebral body and how nerve roots exit be-
tween bodies.IS.19It is also useful in explaining how some
developmental
abnormalities of the spine such as hemiver-
tebraeandcongenitally fusedvertebrae may occur.The the-
oryhasbeenmodified with recent experimental evidence
toconcludethat, whereas the vertebral bodies are formed
byresegmentationthe posterior elements derive mainly
fromthecaudalsomite alone under influence from neural
crestelements.2o Asthe vertebral centers expand, the noto-
chordregresses and notochordalcellstend to migrate to the
intervertebralspace where they contribute to disk forma-
tion, specifically the nucleus
pulposus. Remnants of the no-
tochordmay persist and form chordomas but this occurs
47
Congenital Abnormalities
355
mainly in the coccygealand basisphenoidal regions. sparing
the thoracic spine.
Chondrification begins on day 42 of embryonic life and
continues until age 25.Achondrification center forms later-
allyineachvertebralarchandpropagateslaterallyto forma
cartilaginous vertebral arch with a dorsalexpansionto form
the spinous process. Ossificationfollowschondrification on
day 72oflifeand is enhancedbyfetal movement.Adorsal
and a ventral ossification center fuse to form a single verte-
bral body ossification center. The halves of each vertebral
arch fuse between the ages of 3 and 5 years. In addition to
the usual spinal elements. the thoracic vertebrae must de-
velop ribs and rib articulations. It is believed that the ma-
jority of the rib develops from the somite. Anatomicalevi-
dence suggests that all vertebrae have the potential to
develop ribs (due to the presence of rib process equivalents
on all vertebrae) but only the thoracic somites are able to
express the HOXgene segment needed to form ribs.21
.
SpinalDysraphism
Thetermspinal dysraphism (Greek. raphe-seam)
refers to a
distinct group of congenitalanomaliescharacterizedby a
failureof fusion of midline structures of both ectodermal
and mesodermal origin. The failure of fusion of the bony
posterior elements is termed spina bifida and two types are
recognized, spina bifida aperta and spina bifida occulta.
Spina bifida aperta ranges from exposure of the unfolded
neural plate (myeloschisis) to various meningoceles that ei-
ther involve the spinal cord (myelomeningocele) or the sub-
arachnoid space (meningocele). These conditions are read-
ily apparent at birth. In spina bifida occulta (occult spinal
dysraphism) the dysraphic condition is hidden, being cov-
ered with skin. and may not be detected until later in life.In
contradistinction to open spinal dysraphism. occult spinal
dysraphism (050) involves primarily the spinal cord and
there is no association with Chiari II malformation or hy-
drocephalus.050 encompassesavarietyofclinical condi-
tions including lipomyelomeningocele. diastematomyelia.
and dermal sinus tracts with and without dermoid tumors
and neurenteric cysts (Table47-1).
Table 47-1
ClassificationofNeuralTubeDefects
Open Spinal Dysraphism
Myelomeningocele
Meningocele
Occult
Spinal
Dysraphism
Diastematomyelia
Neurenteric cyst
Lipomyelomeningocele
Lipoma
Dermoid cysts
Dermal sinus tracts
Tethered cord

..
356
ThoracicandThoracolumbarSpine:Pathologyofthe ThoracicandThoracolumbarSpine
.
SpinaBifidaAperta
(Myelomeningocele)
In the UnitedStates the incidence of neural tube defects has
declined from 1.3 per 1000 live births in 1970 to 0.6 per
1000 livebirths in 1989.4The reason for this decline is un-
clear but it may be related to better prenatal care and the
recognition of folate deficiency as a causative factor.The in-
cidence varies worldwide with a rate as high as 8.7 per
1000 live births in Belfast, Ireland. The rate of incidence is
much lower in blacks than in whites. Environmental factors
such as maternal diabetes; maternal deficiencies in folate,
calcium,vitamin C,and zinc; or maternal hyper- or hypovit-
amintosis A have been reported.22.23Teratogen exposure,
such as excessive alcohol use, or anticonvulsants, such as
valproate or carbamazepine, are also linked to an increased
incidence of myelodysplasia. The loss of free radical scav-
enger enzymes associated with the use of anticonvulsants
and the decrease in free radical production by pterin alde-
hyde (a known contaminant of commercial folate) suggest a
possible role for free radicals in the disordered neurulation.
Genetic factors are also important because there is an in-
creased incidence from the baseline 0.1 to 2.5%for subse-
quent offspring in affected families.4 There is also an in-
creased risk of subsequent neural tube defects in children of
sisters and daughters of the mother who has a child with
myelodysplasia. One study suggests that there may be ge-
netic and nongenetic forms of spina bifida, with the genetic
form being an autosomal dominant trait with 75%pene-
trance.24Thus, although no definitive answer has been ob-
tained, it is generally believed that transmission of neural
tube defects follows a multifactorial inheritance pattern
that interacts with environmental factors. Prenatal detec-
tion is suggested by increased
levels of a-fetoprotein
or acetylcholinesterase
in amniotic
fluid or increased
a-fetoprotein levels in maternal serum.
Several associated systemic anomalies are associated
with neural tube defects. Cardiovascular anomalies include
single ventricle, ventriculoseptal and atrial-septal defects,
patent ductus arteriosis, and coarctation of the aorta. Geni-
tourinary defects include single kidney, horseshoe kidney,
hydronephrosis, hydrocele, malrotation,
and exstrophy.
Skeletal anomalies include kyphoscoliosis, pectus excava-
tum, clubfeet,and congenital hip dislocation. Children with
myelodysplasia should undergo a baseline cardiac echo to
rule out cardiacdefects incompatible with survival prior to
closure of the myelomeningocele.
There are severalproposed theories for the embryological
defect that causes spinal dysraphism.2s Generally, it is ac-
cepted that the cause is disordered neurulation with a dis-
turbance in the closure of the neural placode. The earlier
the insult the more severe the resulting malformation. The
higher the level of dysplasia, the less survivable the malfor-
mation. In a study of 510infants who survived the first day
of life, -10% of the lesions were cervical, 5%were thoracic,
25%were thoracolumbar, 33%were lumbar, and 32%were
sacral. The nonclosure theory first proposed by von Reck-
linghausen states that myelodysplasia is due to arrest of the
neural plate closure on approximately day 24 of life, fol-
lowed by a secondary failure of development of the dorsal
spine
elements.
The overgrowth
theory
proposed
by
Ladhoffin 1881 suggests that the failure of the neuraltube
to close results from the overgrowth
of neural tissue inthe
lateral
folds. Padget postulated
a reopening
of the closed
neural tube due to a neuroschistic
bleb. Marin-Padilla and
Marin-Padilla
postulated
that the main cause of spinaldys-
raphism
is a primary
deficiency
of paraxial
mesoderm.
According to Gardner's hydrodynamic theory, the neural
tube closes
normally,
but increased
hydrostatic
pressure
within
the central
canal causes the neural tube to reopen
with subsequent
dysraphism.26
Neurologically,
these
children
present
with functional
motor and sensory levels consistent with their anatomical
lesions. In addition, the presence of the concomitantChiari
II malformation
and hydrocephalus
may contribute toneu-
rological morbidity. These children present with an obvious
deformity
at birth (Fig. 47-1). Abnormal neural tube devel-
opment
prevents
dermis
and epidermis
closure overthe
dorsal
defect.
Dura mater
arises
ventral
to the deformed
spinal cord, but then stretches
laterally over the expanded
pedicles and facets to join the lateral margins of the epider-
mis.
The
dorsal
defect
is covered
by a thin layer of
pia/arachnoid
and
the
zona
epitheliosa,
which is an
extremely
thin layer of epithelium.
In one series, 21%of
infants
with
myelodysplasia
had lumbar
kyphosis. Over
one-third
of these infants
presented
at birth with greater
than 90 degrees of kyphosis and showed linear progression
of their kyphosis over time.27
J
Figure 47-1
Thoracolumbar
myelomeningocele.
Note the neural
placode and the egress of cerebrospinal
fluid from the inferioraspect
of the lesion.

...
47
CongenitalAbnormalities
357
Severaltechniques have been reported for the closure of
themyelomeningocele.28.29Several basic principles
should
beappliedin the early management
of these children. Chil-
drenshould be studied to preclude any cardiac or intracra-
nialabnormalities that would preclude
life. Closure of the
myelomeningoceleshould then be performed
on an early
basis,usually within 48 hours. Children should be started
onantibioticsand kept prone with sterile saline dressings
coveringthe defect until surgery. Anatomical reconstruction
shouldbe attempted with closure of the neural placode, fol-
lowedbya watertight dural closure if possible. Care must
betakento preserve nerve roots and to avoid a dural clo-
surethatis restrictive to the enclosed neural elements. If
possible,theparaspinal muscle fascia is mobilized and ap-
proximated. Thepresence of an associated kyphotic defor-
mitymaycomplicatethe closure and many surgeons prefer
toperforma kyphectomy to allow closure of the subcuta-
neoustissueandskin.Postoperatively,the patients are kept
proneto avoid pressure to the incision, and the hydro-
cephalusthat usually appears is treated with a ventricu-
loperitonealshunt.
Latecomplicationsinclude neurological deterioration re-
latedtoChiariIImalformation with or without shunt dys-
function,spinalcordtethering, and hydrosyringomyelia.3o.3]
Theselatecomplicationsmaybe heralded clinicallyby the de-
velopment
ofscoliosis,weakness,spasticity,and deterioration
ofbowel/bladderfunctionin previously functional children.
. Meningoceles
Dorsalmeningocelesrepresent
a rare condition
in which a
sacofduraandarachnoidcontaining no neural elements ex-
tendsfromanunderlying normal spinal cord and canal. The
absence
of neuraltissue separates this condition from the
morecommonmyelomeningocele.The incidence is approxi-
matelyonemeningocelefor every 10 to 20 myelomeningoce-
les.Thisconditionmost likely represents a postneurulation
disorderof dorsal mesenchymal development. The spinal
cordisnormalandremainsin the spinal canal. Meningoceles
atbirthareusuallycovered with dysplastic or normal skin
andbecauseof this, the AFPlevels in maternal serum and
amnioticfluidarenormal.These children present with a soft
tissuemassthat mayor may not be covered with skin.Their
neurological
examinationis normal. Association with Chiari
malformationand hydrocephalus is uncommon as well as
spinalcolumndeformityat birth or later in life.
. OccultSpinalDysraphism
Spinabifidaoccultarefers to several dysraphic conditions
in
whichthedefectsare hidden by normal skin and may not
benoteduntil later in life. Because the diagnosis is not
readilyapparent at birth, the true incidence of these
Table 47-2
Cutaneous Stigmata of Occult Spinal
Dysraphism
Focalhirsutism("hairypatch")
Capillaryhemangioma
Dermalsinustract
Subcutaneous mass
Rudimentaryappendage
conditions has not been determined.32 Children present
with cutaneous stigmata, pain, orthopedic changes,or neu-
rological changes. The cutaneous stigmata include focal
hirsutism, capillary hemangioma, dermal sinus tract, subcu-
taneous mass, or rudimentary appendage (Table47_2).33.34
Orthopedic changes include scoliosis, leg-length size asym-
metry, and club foot or cavovarus foot deformity.Neurologi-
cal changes include sensory and motor deficits that are
asymmetricand agedependent(Table47-3). Toddlersmay
present with delayed developmental milestones whereas
olderchildrenmaypresent with a combinationofbothup-
per and lower motor neuron signs of one or more extremi-
ties. Boweland bladder dysfunction is common and maybe
heralded by an absence of dry periods between diaper
changes or recurrent urinary tract infections.
As with open dysraphism, the etiology of 050 remains
unclear. Some authors believe that the primary insult oc-
curs when an already closed neural tube ruptures. In-
creased pressure inside the central canal of the neural tube
can cause a rupture that spills highly proteinaceous mater-
ial from the canal into the surrounding tissue. With a de-
crease in pressure, the defect in the neural tube re-anneals
but the proteinaceous fluid inhibits normal development of
the dorsal elements. Because the neural tube has closed,
closure of the dermis and epidermis over the dorsal aspect
of the spinal canal is not impeded. In a simplistic view, most
open spinal dysraphism is caused by a defect in primary
neurulation whereas OSDmay result from a failure of the
secondary neurulation process. Several forms of OSDare
discussed following here.
Table47-3
Signsand Symptoms Foundat Presentation
of Occult Spinal Dysraphism
Cutaneous abnormality
Legweakness
Foot deformity
Urinary incontinence
Fecal incontinence
Sensory changes
Gait abnormality
Scoliosis
48%
48%
39%
36%
32%
32%
16%
14%

358
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
.
Neurenteric Cysts
Neurenteric cysts are infrequently reported congenital ab-
normalities in which displaced endodermal tissue results
froman abnormal connection between the ectodermally de-
rived spinal cord and the endodermally derived foregut.3S-41
During the third week of development,
a transitory
neurenteric canal connects the yolk sac and the amnion. Al-
thoughthis canalnormally should close by day 28, numerous
abnormalities may result from persistence of this canal. So-
matic abnormalities include duplications or malrotations of
the gut and mediastinal masses. Vertebral anomalies are
common and are likely to be in the anterior column leading
to severe kyphotic deformities. Other somatic abnormalities
such as Klippel-Feilanomalies may also be seen (Fig.47-2).43
Histologically, these cysts are lined by ciliated columnar
or pseudostratified epithelium consistent with either devel-
oping or mature foregut structures that may suggest respi-
ratory origin or gut mucosa. Abasement membrane is pre-
sent helping to differentiate these cysts from ependymal
cysts that lack a basement membrane or mucin production.
These cysts most commonly occur in the thoracicor
cervical spine. Children more commonly present with
cutaneous stigmata of 050, whereas older childrenand
adults present primarily with pain. Neurologicaldeficit
as a presenting
symptom
is less common, reflecting
the slow growth of these lesions. As many as 75%of
patients may have cutaneous stigmata at presentation.
In one
series,
there
were
incidences
of associated
diastematomyelia(25%),lipoma(25%),and tetheredcord
(50%).
MRIis the imaging modality of choice. Most lesionsare
isointense to cerebrospinal fluid (CSF)on T1- andslightly
hyperintense on T2-weighted images. A plain radiograph
may demonstrate a hole in the vertebral body wherethere
has been intravertebral extension of a neurenteric cyst-
"the hole in one sign."43
Complete surgical excision remains the treatmentof
choice because subtotal excision is associated withahigh
incidence of recurrence over time. Care must be takenat
surgery not to spill the contents of the cyst becausethe
fluid can initiate significant chemical meningitis.
Figure 47-2
Neurenteric
cyst. Tl-weighted
magnetic
resonance
image of a neurenteric
cyst demonstrating a
connection between the esophagusandspinalcolumn.

. Lipomyelomeningocele
Thetermlipomyelomeningoceleis actually a misnomer be-
causethereisno true herniation of neural elements into a
meningealsac. Instead, the lesion consists of a caudally de-
scendedconus infiltrated
by fatty tissue
that
herniates
throughdural,bony,and fascialdefects to emerge as a skin-
coveredlumbosacralmass, usually in the lumbosacral re-
gion.44It isto be differentiated from the focal intraspinal
lipoma,which will be discussed. There is a female prepon-
derance(1.5:1).45,46
The mass is usually recognized in the
infantand most patients present within the first few
monthsoflife.Symptomsinclude progressive asymmetric
footdeformitiesor leg-length discrepancies. The pathology
maybe due to tethering
of the
cord
or
mass
effect
fromthe lipoma. Chapman and Beyerl have divided
lipomyelomeningocelesinto two distinct variants based on
thelipoma'sdorsal or caudal (terminal) point of origin.47
Thedorsallipomyelomeningocelearises from a dorsally lo-
catedpositionon the caudally descended conus whereas
thecaudallipomyelomeningocele
arises from the terminal
portionoftheconusalmost as a continuation of the conus
itself.Athird form, the transitionallipomyelomeningocele,
whichhasfeaturesof both, has also been described (Fig.
47-3).Withadorsallipomyelomeningocelea large subcuta-
neousmassisalmost always present and both the sensory
Figure47-3 Transitionallipomyelomeningocele.
Note the presence
oflipomaboth dorsal and ventral to the nerve roots.
47
CongenitalAbnormalities
359
and motor roots arise in a plane ventral to the lipoma,
allowing for easier preservation during surgery. In a caudal
lipoma the nerve roots may arise intimately in association
with the lipoma. The lipoma may rotate the cord causing
the dorsal surface to face laterally or posterolaterally. The
roots arising from the deep side of the cord are much
shorter than the roots arising from the superficial side of
the rotated spinal cord and may also serve to tether the
cord. Plain x-rays are almost always abnormal, with dorsal
fusion of the lamina (spina bifida) being the most common.
MRIis the imaging modality of choice for diagnosis and to
define the anatomy. The fatty tissue will appear bright on
both T1- and T2-weighted images.
The natural history of untreated lesions isthat of progres-
sive loss of neurological function. It is recommended
therefore that all lipomyelomeningoceles
should be ex-
plored.44.47,48
Surgicalgoalsshouldbe to releasethe tether,
debulk the lipoma, and re-create the dural sac.Theadipose
tissue is traced to the fascial defect and the fascia isopened
above the defect. Bonyremoval should extend abovethe de-
fect because normal dura should be opened rostral to where
the lipoma enters the cord. With the dorsal variant the key
at surgery is to recognize the junction of the lipoma with
the spinal cord complex and the position of the dural at-
tachment in relation to that complex. This allows preserva-
tion of the roots during surgery. With the caudal variant the
nerve roots traverse the lipoma and are at risk during de-
bulking. Nerve stimulation and rectal/bladder monitoring
are useful during surgery. After the cord is released, the car-
bon dioxide laser is used to vaporize enough fat to allow
dural closure without compression of neural elements from
fatty tissue.
. lipomas
Some intradural intramedullary spinal lipomas are not as-
sociated with spinal dysraphism (Fig. 47-4). These tumors
are rare, accounting
for -0.6%
of all intraspinal
tu-
mors,44,49.50and show no male or female preponderance.
They are most commonly located in the thoracic region and
usually found dorsally in the midline. These lipomas are
not true neoplasms and increase in size only in relation to
other adipose tissue in the body. They are usually subpial,
involve several spinal cord segments, and have no cleavage
plane between the lipoma and the cord. Histologically
these tumors appear as normal adipose tissue with a col-
lage matrix and occasional microfoci of calcification.These
lesions most likely result from the inclusion of adipose
cells from the overlying mesodermal tissue into the devel-
oping spinal canal or folding neural tube. Although some
patients maypresent within the firstyearoflife, the most
common age of presentation
is in the second or third
decade. The patients most often present with an ascending
spastic paresis of one or both legs or a suspended sensory
loss suggesting an intramedullary lesion. Bowelor bladder
symptoms may occur if the conus is involved.Radicular
symptoms are rare.52Radiologically these tumors can be

360
Thoracicand Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
Figure 47-4
Spinal lipoma, intraoperative view. Thispatient pre-
sented withpainlessweaknessofthe right leg.
diagnosed by their high signal intensity on both Tl- and
T2-weighted images. Although this pattern is sometimes
seen with hemorrhage, the clinical history of slowly pro-
gressive symptoms should make the diagnosis evident. On
CTscans these lesions appear as very low signal attenua-
tion but this pattern can also be seen in dermoids and epi-
dermoids.49
The goalof surgery is not total excision due to the lack of
a surgical plane and the high risk of neurological injury. A
standard midline approach
is used
with
appropriate
laminectomies for exposure. Subtotal excision is preferred
to debulk the lipoma and allow dural closure. The carbon
dioxide laser is a useful tool to shrink the tumor given its
high water content. Usually, the debulking is associated
with a return to normal and a single operation is curative
with not enough regrowth of the residual lipoma to cause
neurologicalsymptoms.44
.
Diastematomyelia (SplitCord
Malformations)
There are two types of split cord malformations that have
been described (diastematomyelia and diplomyelia) but
both conditions are commonly included under the term
diastematomyelia. Diastematomyeliaactually refers to a type
of double cord malformation in which there are two hemi-
cords that are contained in two separate dural sacs, sepa-
rated by a bony spur. This differs from the condition
diplomyelia in which two separate cords are containedin
one dural sac without an intervening spur.S3
These conditions may represent opposite endsofaspec-
trum of split cord malformations
(SCMs)accordingto
Pang's unified theory. In Pang's unified theory, a typeISCM
refers to two hemicords each housed within its owndural
tube separated by a dural, sheathed, rigid, osseocartilagi-
nous median septum. A type II SCMrefers to two hemi-
cords housed within a singledural sheath separatedonly
by a nonrigid fibrous sheath. The SCMtheory proposedby
Pang states that both types of SCMsoriginate fromoneem-
bryological error around the time of neural tube closure.
The basic error occurs when the accessory neurenteric
canal forms through the midline of the embryonicdisk,
which maintains communication between the endoderm
and the ectoderm. When the abnormal fistula develops,
mesenchyme condenses around it and the tract splitsthe
developing notochord and neural tube. The malformation
phenotype depends on further spinal column/corddevel-
opment. An SCM results if the embryo is able to heal
around the tract. If the tract picks up primitive cellsfrom
the mesenchyme destined to become the meninges,the
two hemicords will each be invested in dura mater.The
dura mater can stimulate bone growth that resultsinthe
midline spur seen in the type I SCM.In Pang'sseriesof
39 patients, 19 patients had type I SCMsand 18patients
had type II SCMs with two patients
having composite
lesions.Althoughit has long been thought that thepres-
ence or absence of medial nerve roots aided indistinguish-
ing diastematomyelia
from simple diplomyelia, he found
that medial nerve roots occurred in 75%of both typeIand
type II SCMS.54
Both conditions may lead to tethering and neurological
deficits. In a study of 60 patients, Hood et al foundthatdi-
astematomyelia occurred from the third thoracicvertebrato
the fourth lumbar vertebra, with a prevalence of50%inthe
thoracicand 50%in the lumbarregions.55Thereisastrong
femalepreponderancefor diastematomyelia.Inastudyof
43 affected patients, Milleret al found that 79%hadcongen-
ital scoliosis and 84% had some neurological manifesta-
tion.56
There is a high association between these lesionsand
the presence of a hairy patch.53.57The diagnosis maybe
suggested on plain x-rays by the presence of a midline
bony spur, a widened interpedicular distance, scoliosis.or
bony segmentation
errors.
Although
MRI is a good
method for screening modality, many authors believethat
CTmyelography remains the imaging procedure ofchoice
to define the anatomy of the hemicords and the presence
of a tethering midline spur, which may be bony or fibrous
(Fig. 47-5).
All patients,
even those who may be asymptomatic,
should be explored.53.55.58The laminectomy shouldbecar-
ried at least one segment above and below the septum.
Patients with two hemicords in a single dural sacwithouta
demonstrable spur need exploration because fibrousadhe-
sions are usually present and cause tethering of the cord.
Care must be taken during the laminectomy to recognize

47
CongenitalAbnormalities
361
Figure47-5
Diastematomyelia.Axialsection of a thoracic spine computed tomographic scan. Note the presence of the diagnostic midline bony spur.
anydorsalattachments
of the median
septum
that
may
torquethe cord on removal. The bony spur may be re-
movedbya rongeur or a high-speed
drill (Fig. 47-6).
The
ventraldura is usually violated but need not be closed. All
midlineadhesionsare lysedand the dura is closed posteri-
orly.Painresponds best to surgical
therapy,
followed
by
sensorimotorcomplaints.
Bowel and bladder
loss is least
likelyto return after surgery, stressing
the need for early
surgicalintervention.
Figure47-6
Diastematomyelia. intraoperative view after removal of
bonyseptum. Note the presence
of the two hemicords.
.
Dermoids, Epidermoids, and Dermal
Sinus Tracts
Dermal sinus tracts occur once in each 1500 births and are
manifested
as a pit that occurs above the intergluteal
crease with a sinus tract lined by squamous epithelium
that penetrates the spinal cord anywhere from the lum-
bosacral spine to the occiput (Fig. 47-7).59 The position of
J
J
,
Figure 47-7
Epidermoid cyst. Tl-weighted magnetic resonance imag-
ing scan. The lesion ischaracteristically isointense with cerebrospinalfluid.

362
Thoracicand Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
the pit above the gluteal crease differentiates the dermal
sinus tract from a benign, blind-end pilonoidal pit (sacro-
coccygealdimple), which is always within the intergluteal
cleft and is an incidental finding in -5% of all newborns.50
Dermal sinus tracts are lined by a stratified squamous ep-
ithelium and may traverse several spinal levels before pen-
etrating the dura and attaching to the filum or spinal cord.
Intradurally, they may be accompanied by any of the major
dysraphic abnormalities and about half end in a dermoid or
epidermoid. Dermoids contain elements from two germ
layers (Le., hair, sweat, and sebaceous glands), whereas
epidermoids contain only desquamated cells from the epi-
dermal layer. These tumors are also encountered within
the subarachnoid space arising from isolated congenital
rests of cells derived from the multi potential caudal cell
mass. Patients present with unexplained bouts of meningi-
tis (usually Staphylococcus aureus or Escherichiacoli) that
recur despite appropriate antibiotic coverage.51 Patients
also present with signs and symptoms related to tethered
spinal cord or neural compression. MRIis the diagnostic
imaging of choice to demonstrate where the tract violates
the dura and to show any associated cyst. Dermoids fre-
quently appear isointense on T1 sequencing and hyperin-
tense on T2-weighted images.52There is no role for conser-
vative
therapy,
and
surgical
intervention
should
be
undertaken once the diagnosis is made. An elliptical inci-
sion is made to excise the pit and the tract is traced to
where it violates the lumbodorsal fascia (Fig. 47-8). It is
then followed down with bone removal done as necessary
until the dural defect is identified. The dura is also opened
elliptically around the tract. After the dura is opened, any
attachments or adhesions are lysed and any associated cyst
is removed.
~
Figure 47-8
Dermal sinus tract. Note the probe passing throughthe
tract and a defect in the lamina.
.
Tethered Cord Syndrome
(Tight Filum Terminale)
The syndrome
of the tethered
cord is usually listed inthe
classifications
for OSD when in fact it is a clinical entity,not
a structural
entity.53 Tethered
cord syndrome
is a seriesof
clinical findings related to traction
on the conus medullaris
when the spinal cord becomes affixed to a structure suchas
a lipoma, lipomyelomeningocele, dermal sinus tract,ordi-
astematomyelia
(Fig. 47_9A,B).54-57The spinal cord canalso
B
Figure 47-9
Tethered cord from a lipoma. (A) Tl-weighted
mag-
netic resonance image (MRI), sagittal view. Note the descended
position of the conus.(8) Tl-weighted MRI,axialview. Note the pos-
terior position of the filum.
A

47
CongenitalAbnormalities
363
be tethered as a result of previous surgery such as in a
myelomeningoceleor lipoma repair. It is believed that is-
chemicchanges in the conus lead to deranged oxidative
metabolismand cord dysfunction.
The term tight filum terminale refers to the condition
wherethe tethered cord syndrome is caused by a filum that
isshort and abnormally thickened (> 2 mm) and tethers
theconus medullaris below the normal L1-L2 level. Often
therewillbe abnormal fat within the filum.66.68
Theclinicalpresentation of patients with a tethered cord
by any mechanism is widely variable but age-specific
patternsare recognized. Children rarely present with pain.
Insteadthey present with bladder dysfunction, gait abnor-
malities,foot deformity or leg-length discrepancy, cuta-
neousstigmata, or progressive spinal deformity.68 Adults
morecommonly present with pain, leg weakness, and uri-
naryfrequency.64.69Radiographic imaging includes MRIto
notethelevelofthe conus,the presenceoffat in the filum,
andany intraspinal pathology. CT myelography helps to
delineatethe direction of the exiting roots.
Treatmentis directed at releasing the cord from whatever
lesiontethers it. Forpatients with abnormal fila sectioning
thefilumis effective but care must be taken to ensure that
it is the filum that is being sectioned and not a caudally
stretchednerve root. Becausethe natural history of tethered
cordsyndrome is one of inexorable progression, and neuro-
logicaldysfunctionis notalwaysreversedwithsurgery,pro-
phylacticsurgery is recommended once a tethering lesion is
recognized.70
Recentattention has focused on the management of pa-
tientswho present with clinical evidence of a tethered cord
withradiographic imaging suggesting that the conus is in
normalposition (L2 or above).71 Sectioning the filum in
thesepatientshas been showntobe effectivebut the num-
bersof patients studied has been small, and long-term
follow-uphas been limited.
. Congenital Anomalies of Vertebral
Bodies
Congenital Scoliosis
Congenitalscoliosis is an abnormal curvature of the spine
inthe coronal plane that develops when anomalous verte-
braeare present at birth. Bydefinitioncongenitalscoliosis
differsfrom the idiopathic scolioses (Le., infantile, juve-
nile,adolescent)
because the idiopathic
forms have no
structural vertebral abnormalities (Table 47-4). The ver-
tebralanomalies in congenital scoliosis are usually due to
failureof formation or segmentation
of one or more ver-
tebrae. Although the vertebral anomalies are present at
birth,in congenital scoliosis the spinal deformity is rarely
noticeable during infancy.72 Patients with mild or com-
pensated deformities are often diagnosed as adults when
vertebral anomalies are discovered
incidentally during
routine radiographs. Differences in number, location, and
Table 47-4
Classification of Scoliosis
Congenitalscoliosis
Scoliosisdueto congenitallyanomalous
vertebraldevelopment
Idiopathicscoliosis
Astructurallateralspinalcurvature for
whichno causeisestablished
Infantilescoliosis
Spinalcurvaturethat developsduring
the first 3 years of life(0-3 years)
Juvenilescoliosis
Spinalcurvaturethat developsbetween
age 3and puberty(3-10years)
Adolescentscoliosis
Spinalcurvaturethat developsat or
about the onset of puberty
(10 years
to maturity)
Neuromuscular scoliosis
Scoliosis due to a known abnormality
of the central nervous system or of
the muscles and nerves
type of vertebral
anomalies
can account for the wide
range
of clinical
presentations
seen
in
congenital
scoliosis.3.73-76Congenital scoliosis is less common than
idiopathic scoliosis. The genetics of congenital scoliosis
are not well understood, but the risk of familial transmis-
sion is inherently low. In one series, the incidence of mul-
tiple family members with congenital spinal deformity
was on the order of 1%.3Additionally, many patients with
congenital
scoliosis have associated
intraspinal
anom-
alies. In a series of 251 patients with congenital scoliosis
reported by McMaster, 18%of patients had an associated
occult intraspinal anomaly.77 The most common finding
by far was a diastematomyelia but neurenteric cysts, der-
moids, epidermoids,
teratomas,
and lipomas were also
noted. Congenital scoliosis can be associated with a vari-
ety of cardiac, genitourinary, and skeletal abnormalities
(Table 47-5).14
Normal growth of the spine occurs at the end plates at
the upper and lower surfaces of the vertebral bodies. Con-
genital vertebral
anomalies
can cause functional defi-
ciency of the growth plates on one or both sides of the
spine. Aspine deformity will occur if there is asymmetric
growth, which occurs as a functional deficiency on one
side as compared with the other. The rate of angulation
and the final severity of the congenital scoliosis are pro-
portional to the degree of growth imbalance produced by
the vertebral anomalies. The portion of the vertebrae with
deficient growth determines whether a pure scoliosis oc-
curs or whether
there will be a component of sagittal
plane deformity with a component of kyphoscoliosis or
lordoscoliosis. In general, 25%of all congenital scoliosesdo
not progress,
50% progress
slowly, and 25% progress
rapidly.76.78To classify and predict the natural history of
congenital scoliosis, Winter and Moe Eilers developed a
classification
system for congenital spinal deformities
based on the embryological development of the spine. This
system divides the anomalies into (1) failures of segmen-
tation, (2) failures of formation, and (3) mixed anomalies.
Using this system they were able to classify up to 80%of
all abnormalities.76

T
364
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
Table47-5
CongenitalSpinalDeformity
Errors of Segmentation
Congenital scoliosis (lateral)
Unilateral bar
Blockvertebrae
Errors of Formation
Congenital scoliosis (lateral)
Fullysegmented
hemivertebrae
Semisegmented
hemivertebrae
Incarcerated hemivertebrae
Nonsegmented
hemivertebrae
Congenital lordosis (posterior)
Congenital kyphosis (anterior)
Wintertype II
Spina bifida (posterior)
Congenital kyphosis (anterior)
Wintertype I
Combined Errorsof Formation and Segmentation
Congenitalscoliosis(lateral)
Unilateralbarwithhemivertebrae
.
Errors of Segmentation
Segmentationfailurecausesa bony fusion between
verte-
brae (Fig. 47_10).79.80Defects of segmentation
can be unilat-
eral or bilateral. A block vertebra is a bilateral segmentation
defect involving two or more vertebrae
resulting in a loss of
Block Vertebra
Bilateral
failure of
segmentation
Hemivertebra
Fully segmented
Semi-segmented
Defects of Segmentation
Unilateral Bar
Unilateral
failure of
segmentation
Congenital
kyphosis (anterior)
Winter type I
the growth plate bilaterally between the vertebrae. The
spine is shortened but there is little propensity for progres-
sion because the disk spaces are either dysplasticor fused.81
On the other hand. a unilateral
unsegmented
bar isa unilat-
eral segmentation
defect
where
one side of the spineis
fused and the other side is left with normal activegrowth
Unilateral Bar &Hemlvertebra
Wedge Vertebra
Figure 47-10
Congenital
scoliosis (reproduced
with permission from MacMaster82).
Defects of Formation
Incarcerated
Nonsegmented

47
Congenital Abnormalities
365
Figure47-11
Hemivertebra
with contralateral
unsegmented
bar.
plates.Thisimbalance in growth results in scoliosis with the
unsegmentedbar in the concavity.Becausegrowth potential
existson only half of the spine the potential for deformity is
significant.On average these curves deteriorate at a rate of
-5 degrees per year and will result in a significant defor-
mityby puberty.81The unsegmented bar in association with
acontralateralhemivertebra has the highest risk of progres-
sion,up to 10 to 12 degrees per year (Fig.47-11 ).81.82In a re-
cent series of 43 patients with this specific anomaly re-
portedby McMaster, these deformities progressed at a rate
ofat least 6 degrees per year and all exceeded 50 degrees by
age4.83Surgical treatment in children over 5 years old was
unsuccessfulin correcting these rigid deformities. Therefore,
McMasterrecommended a combined anterior and posterior
prophylacticsurgical treatment in the first year of life.Surgi-
caloptions include posterior spinal fusion with or without
instrumentation,or anterior and posterior exposure with fu-
sion,epiphysiodesis,or hemivertebral excision.Epiphysiode-
sis relies on growth (preferably normal growth) on the
concaveside of the curve to achieve correction.
. Errors of Formation
Failureof formation can range from mild wedging to total
absenceof the vertebra (Fig.47-10). The complete absence
ofhalf of the vertebra results in a hemivertebra that has
halfof a vertebral body, one pedicle, and one hemilamina.
Inthe thoracic spine there is a rib attached to the hemilam-
inaresulting in an unequal number of ribs. The hemiverte-
bra is the most common cause of congenital scoliosis.
Thereare three types of hemivertebra, which are classified
both by the relationship of the hemivertebra to the adja-
centvertebrae and whether the associated disks are mor-
phologically normal. A hemivertebra's potential to cause
significant scoliosis depends on its type, location, the num-
ber of hemivertebrae, their relationships (ipsilateral
or
contralateral), and, finally,the patient's age and growth po-
tential. Forexample two fullysegmented hemivertebrae on
the same side of the spine will have a much greater poten-
tial for deformity than either a single hemivertebra or two
hemivertebrae
on opposite sides of the spine. Also, a
hemivertebra located at the thoracolumbar or lumbosacral
junction is much more likely to cause deformity and clini-
cal symptoms.
Afully segmented hemivertebra has a normal disk space
above and below the formed portion of the vertebral body
and no vertebral body on the unformed side. Becausenor-
mal growth occurs on one side only the potential forsignifi-
cant deformity exists. The hemivertebra acts like an enlarg-
ing wedge and is located at the apex of the convexityof the
scoliosis. The rate of progression for a single fully seg-
mented hemivertebra depends on its location in the spine,
with the worst prognosis for those located at the thora-
columbar junction. The normal rate of curve progression is
1 to 2 degrees a year but some will have a more rapid pro-
gression requiring surgical correction.81,84
An incarcerated hemivertebra is a variant of the fullyseg-
mented hemivertebra in which the hemivertebra is set into
defects in the vertebrae above and below it. The incarcer-
ated hemivertebra is small, ovoid, with poorly formed disk
spaces. The defects in the adjacent vertebrae tend to com-
pensate for the hemivertebra, and the poor growth poten-
tial of the malformed growth plates results in less scoliotic
deformity
when
compared
with
the
standard
fully
segmented hemivertebra.84
Asemisegmented hemivertebra is fused to either the ver-
tebrae above it or those below it. This results in the absence
of one disk space on the side of the hemivertebra with
obliteration of two growth plates (one from the hemiverte-
bra and one from the adjacent vertebrae). This results in
similarly impaired growth on both sides of the spine be-
cause two active growth plates exist on each side. Scoliotic
deformity is usually mild to modest in this situation and
most patients with semisegmented vertebrae do not require
treatment.
Anonsegmented hemivertebra is fused to the adjacent ver-
tebrae above and below it with no disk spaces or growth
potential present. The wedge shape of the hemivertebra
may cause a small amount of nonprogressive deformity,
which may in fact be slowly corrected with growth on the
opposite side.
There are three treatment choices for the patient with a
fully segmented hemivertebra. A combined anterior and
posterior fusion can be performed to prevent progression
of the deformity. A second option is hemiepiphysiodesis.
An anterior and posterior hemiepiphysiodesis is a two-step
procedure to halt growth on the convexity of the curve and
allow for compensatory growth to remain on the concavity
of the curve with subsequent correction of the deformity.
Through an anterior approach, the convexity of the curve is
identified and half of the vertebral end plates are removed
in conjunction
with an anterior spinal fusion to halt
growth. A similar procedure is performed via a posterior
approach. Young patients with a curve that involves five or

.
366
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
fewer segments and has a magnitude less than 50 degrees
are suitable candidates for this procedure. The third option
is hemivertebra excision.This is the procedure of choice for
lumbar hemivertebrae, particularly for an L5hemivertebra,
which has a high risk of later truncal imbalance. Hemiver-
tebral excisionfor a single hemivertebra had been reported
in the early literature
to have a high morbidity
with
surgery. Slabaugh et al reviewed
eight patients
with
hemivertebrae treated with excision and noted one death
and three patients with significant but transitory neurolog-
ical deficits.85Recently, Callahan et al reported a series of
10patients with a single hemivertebra treated with a com-
bined anterior/posterior
approach for excision and fusion
and reported no morbidity with surgical treatment.86 Other
recent reports have shown improved outcomes with this
procedure.3.87
.
CongenitalKyphosis
Congenital kyphosis is an uncommon sagittal plane defor-
mity.Although it is rarer than other forms of scoliotic defor-
mities, its consequences are more severe, with a high likeli-
hood of neurological deficit if left untreated. It is the most
common cause of paraplegia in patients with noninfectious
spinal deformity.89-94The cause of the kyphosis is failure of
either formation or segmentation of a portion of the ante-
rior column (Le.,the vertebral body). Winter et al classified
congenital kyphosis into three patterns: type I-failure of
vertebralbodyformation,type II-failure ofanterior verte-
bral body segmentation
resulting in an anterior unseg-
mented bar, and type III-a mixed failure of formation and
segmentation (Fig.47-12A-C).75The type Ikyphotic defor-
mity is the most common and the most likely to progress
rapidlyand cause neurological deterioration. The severity of
the deformity is directly proportional to the amount ofver-
tebral body that fails to form (Fig. 47-13A,B). Avariantof
the type I error is a central and anterior failure of formation
producing
a "butterfly
vertebra"
(Fig. 47-14).95 The typeII
kyphotic
deformity
is rarer and produces
a less severede-
formity that is less likely to progress to neurological deficit.
The etiology of the vertebral
body aplasia or hypoplasiais
not well defined.
Initially, sclerotomal
absence or malfor-
mation was proposed
but total disruption
of the sclerotome
would lead to posterior
arch abnormalities,
which are not
typically seen in pure congenital kyphosis. One current the-
ory proposes
that there
is a lack of vascularization
ofthe
developing
centra
of the vertebra
during the end of chon-
drification or during ossification.
The kyphosis
is progressive
and -50% of these patients
will present
with
some neurological
signs or symptoms.
Symptoms are a result of compression of the spinalcord
and nerve roots. The most common
initial presentation is
neurogenic
bladder. Other symptoms
include lower extrem-
ity abnormalities
such as pain and weakness
as well asor-
thopedic
abnormalities
such as equinocavocarus
deformi-
ties of the feet. The inherent instability of these kyphotic
deformities places these patients at significantriskforcata-
strophic neurological injury after minor falls or trivial
trauma. Children often present with acute paraplegiaanda
"dislocated"
spine.96.97
There is no clinical experience to support bracingorother
nonoperative management for congenital kyphosis.Fortype
I lesions, the ideal treatment is a simple posterior fusion
without instrumentation
provided the child is between1
and 5 years of age. Forchildren older than 5 years,posterior
fusion can be done if the angle of kyphosis is lessthan55
degrees. If a posterior
approach alone is employedin
patients
with
greater
than
55 degree
kyphosis,the
pseudarthrosis
rate may be as high as 54%.Therefore, forall
adults and for children
over 5 years of age whose kyphosis
is greater
than 55 degrees,
a combined
anterior/posterior
approach is preferred.93.98The anterior surgery allowsthe
A
Figure 47-12
CongenitalkyphosisWinterclassification.(A)TypeI:failureofformation.(8) TypeII:failureof segmentation. (C)TypeIII:Mixedfail-
ure of formation and segmentation.

47
CongenitalAbnormalities
367
A
-,"0/"
BII!lig=::~::l:;;;;~2ig::::;;;:::":
.':_;::
B
Figure47-13
Congenital kyphosis. (A. B)Anteroposterior
and lateral radiographs of a 6-year-old male who was noted to have an abnormality on a
chestfilmduringasthma evaluation. He has a Winter type Icongenital kyphosis with failure of formation of the anterior elements of T11.
Figure47-14
Butterfly vertebra.
releaseoftethering structures that prevent the correction of
thekyphosisand allows insertion
of bone grafts to restore
heightandachievesolidunion. Forthe less common type II
kyphosis,treatment is posterior fusion one level above and
belowthesegmentationdefect. Ifthe kyphotic deformity is
advanced,then it may be necessary
to perform an anterior
osteotomyof the unsegmented
bar followed
by posterior
stabilization.
.
CongenitalLordosis
Congenitallordosisis rarer than either congenitalscoliosis
or congenital kyphosis.99.lOo
This condition results from dor-
sal defects in segmentation growth. Congenital lordosis is not caused by a failure of for-
mation. There may also be a deformity in the coronal plane
with a lordoscoliosis when the location of the unsegmented
bar is dorsolateral. The most common complication ofcon-
genital lordosis is development of a severe impairment of
pulmonary function, making it a potentially lethal defor-
mity. Winter et al report the case of a child with congenital
lordosis who died at age 9, whose autopsy revealed that the
anterior aspect of the spine was only 8 mm from the poste-
rior wall of the sternum.3
There is no role for conservative therapy once the diagno-
sis is made. The plan for surgical correction is either one of
stabilization or one of correction depending on whether the
patient has presented prior to the onset of major deformity.
Apreventive operation requires anterior arthrodesis of the
involved segments and one or two vertebrae above and be-

368
Thoracicand Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
low the lesion. Acorrective operation for major deformity
requires a combined anterior/posterior
approach. First an
anterior approach is performed with generous osteotomies
removing the disk and anulus but leaving the posterior lon-
gitudinalligament
and posterior anulus intact as a stable
hinge and close when the posterior operation is completed.
A second posterior procedure requires multiple posterior
osteotomies at the same levels of the anterior osteotomies.
Sublaminar wires are then passed and contoured over a
Luquerod for correction use of a posterior rod construct to
create
a kyphosis.IOO
.
Segmental Spinal Dysgenesis
Segmental spinal dysgenesis is a rare congenital anomaly of
the thoracolumbar spine consisting of focal agenesis or dys-
genesis of one or more vertebrae resulting in severe spinal
deformity or instability.lol-104The lesion is most commonly
located at the thoracolumbar junction. The defect includes
hypoplasia of all the vertebral elements, including the ver-
tebral body, pedicles, lamina, and spinous process (Fig.
47-15). The result is an amorphous osseous ring with focal
and severe spinal stenosis. Thiscondition differs from other
agenesis syndromes such as sacral agenesis in that it lacks
spinopelvic instability, lower extremity malformations, and
fixed neurological deficit. Interestingly, the distal bony ele-
ments and spinal canal are usually normal. Neurological
function in these patients ranges from normal to paraplegic.
Thecause is unknown but an association with various med-
ications, toxins, and maternal diabetes has been noted.IOI
Others have suggested
an aberrant
or absent vascular sup-
ply.lo2A radiographic
definition
proposed
by Faciszewskiet
al includes the following characteristics: (1) focalareaof
stenosis, (2) spinal canal of hourglass shape with noneuro-
central junctions,
(3) ring of bone encircling the posteriorly
positioned
spinal canal with no pedicles or spinous process
attached at this level, (4) a fat-filled space anteriortothe
bony ring, and (5) no osseous
abnormalities
caudad tothe
involved level.lol
This disorder
most commonly
results in kyphosis andis
differentiated
from the congenital
kyphosis with failureof
formation
described
by Winter by the presence ofpedicles
and posterior elements
and the absence of spinal stenosisin
congenital
kyphosis.
Also, the severe spinal stenosis isab-
sent in congenital
kyphosis. Segmental
spinal dysgenesisis
differentiated
from the kyphosis
of myelomeningocele by
the absence
of stenosis
and the presence
of a fixed neuro-
logical deficit in the latter.
In a series of patients followed by Flynn et al severalpa-
tients experienced significant neurological deficitwhile
awaiting
surgery,
leading
them
to recommend
that pa-
tients
should
be
operated
on
once
the
diagnosis is
made.102 Treatment
should
be directed
at the establish-
ment and maintenance of spinal stability and to arrestthe
progressive kyphosis. Surgical treatment usually requires
a combined
anterior
and posterior
arthrodesis
and isbest
performed as early as possible. Contrary to early reports,
use of instrumentation
even in the very young has been
shown
to be a safe and valuable
adjunct
to achieve solid
bony fusion.
Figure 47-15
Segmental spinaldysgenesis.Axialsec-
tion of a thoracic spine computed
tomographic scanina
13-year-old patient with segmental
spinal dysgenesis.
Note the absence of the pedicles.

. Dysplastic (Congenital)
Spondylolisthesis
Spondylolisthesisis the slippage of all or part of one ver-
tebraontoanother.105Several different etiologies have
beenidentified with this condition. The role of upright
posturecontributing
to this condition
is well recog-
nized.lOG
Spondylolisthesisis extremely rare during in-
fancy.107.108
Newmannoted the associationof spondyloly-
siswiththe onset of ambulation in early childhood.lo9.noIt
hasbeen suggested that spondylolisthesis
results from a
congenitaldefect or dysplasia that causes the develop-
mentofa pars defect due to the stresses of upright pos-
Normal
Type I
TypeII-A
Type II-B
Type IV
47
Congenital Abnormalities
369
ture and lumbar lordosis. The most widely accepted clas-
sification of spondylolisthesis is by Wiltse et al. They di-
vided spondylolisthesis into five types: type I-dysplastic
spondylolisthesis. type II-isthmic spondylolisthesis. type
III-degenerative
spondylolisthesis.
type IV-traumatic
spondylolisthesis. and type V-pathological
spondylolis-
thesis.111Wiltse and Rothman later suggested a common
congenital component in the etiology of dysplastic and
isthmic spondylolisthesis
and further refined classifica-
tion of spondylolisthesis (Fig.47-16).112
Dysplastic spondylolisthesis accounts for 14 to 21%of the
cases of spondylolisthesis with a 2:1 female to male ratio.107
This type is characterized by structural anomalies of the
Type II-C
Type V
Figure 47-16
Wiltse classification of spondylolisthe-
sis (reproduced
from Wiltse et al and Bradford and
Hu111.113).Type I:dysplastic congenital deficiency ofthe
superior sacral and inferior fifth lumbar facets. Type II:
isthmic; II-Alytic (fatigue fracture of the pars): II-Belon-
gated but intact pars: 11-(acute fracture of the pars.
Type III:degenerative
(facet joint degeneration
allows
translation,
usually L4on LSin older patients). Type IV:
traumatic
(acute fracture in a region other than the
pars). Type V: pathological attenutation
of the pedicle
secondary to structural weakness in the bone.

370
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar
Spine
lumbosacraljunction, including dysplasia of the lamina and
facetjoints. The lack of the normal facet buttress provided
by normal facet joints predisposes toward slippage of the
superior vertebra on the inferior one. The dysplastic articu-
lar processes may be oriented in the axial or sagittal planes.
In axial dysplasia, the articular processes have a horizontal
orientation and this condition is often associated with spina
bifida. In sagittal dysplasia, the facet joints are often asym-
metric but the neural arch is usually intact and therefore
high-grade slippage seldom occurs. Both types can present
with hamstring spasm, back or leg pain, or neurological
deficit including paresthesia, weakness, or, rarely, inconti-
nence of the bowel or bladder. Neurologicaldeficits are usu-
allyassociated with high-grade slips.
Axially oriented facet joints associated with spinal bi-
fida have an increased risk for high-grade spondylolisthe-
sis. The pars interarticularis is often poorly developed and
may elongate, develop a defect, or remain intact. If the
pars interarticularis
remains intact, neurological symp-
toms usually occur only when the spondylolisthesis
ex-
ceeds 35%.Progression of spondylolisthesis is more likely
in younger or skeletally immature patients and patients
with wide spina bifida. Initial treatment should be nonop-
erative unless progression is documented in the younger
patients or slippage is greater than 50%at time of initial
evaluation.
Fusion in situ is the most frequently
per-
formed surgical procedure, although some surgeons uti-
lize reduction and fixation, especially in high-grade slips
(Fig. 47_17).108.113
Figure 47-17
Spondyloptosis.SagittalTl-weighted magnetic reso-
nance image of an 8-year-old asymptomatic patient with a grade V
spondylolisthesis(spondyloptosis).
Spondylolisthesis in patients with sagittally oriented
facet joints and intact L5 lamina is frequently
treated with
decompression along with fusion resulting in morerapid
resolution
of hamstring
tightness and spasm.
.
Klippel-FeilSyndrome
Klippel-Feil syndrome
was initially described as a triadcon-
sisting of a low hairline, short or absent neck, and restricted
neck range of motion. The syndrome
is commonly applied
to patients with congenital fusion of the cervicalspinebut
it often has associated
fusion abnormalities
of the thoracic
and thoracolumbar
spine.1I4 Thomsen et al divided patients
into three types.liS Type Ipatients (40%of their group)hada
combination
of lower cervical and upper thoracic congeni-
tal fusion. Type II patients
(47%) had cervical spine involve-
ment only, and type III patients
(13%) had involvementof
both cervical and lower thoracic or upper lumbarspine.
They found an incidence
of associated
scoliosis in up to70%
of these patients
but with very slowly progressing curves.
Conversely,
Klippel-Feil
occurs
in 25% of patients with
congenital
scoliosis. In his review of Klippel-Feil patients.
Winter
et al found
that
only
2% of cervical anomalies
required treatment
but the associated scoliosis in other
parts of the spine was treated in the majority of cases.116
.
IntraspinalCysts
The congenital
spinal meningeal
cyst is an uncommon clini-
cal entity with a confusing terminology.
These cysts maybe
either
intradural
or extradural
in 10cation.117.lIsRecently,
Nabors et al proposed
a classification
system based onloca-
tion and histological diagnosis.1I9 They proposed three
groups: (1) extradural
meningeal
cysts without spinalnerve
root fibers (dural diverticula, root sleeve dilatations,per-
ineural
cysts,
sacral
meningoceles);
(2)
extradural
meningeal
cysts with spinal nerve root fibers (Tarlov'scysts,
perineural
cysts,
spinal
nerve
root diverticula);
and (3)
intradural
meningeal
cysts (arachnoid
cysts,leptomeningeal
cysts, ependymal
cysts ).117.119-124
.
Intradural
Spinal Cysts
Arachnoid
cysts (leptomeningeal
cysts) would correspond
to a Nabors type IIIintradural spinal meningeal cyst.These
cysts can occur anywhere
along the spinal arachnoid space
although they are most common in the thoracic region
(Fig. 47-18A,B).
They most commonly
assume a position
dorsal to the spinal cord although anterior cases havebeen
reported. There has been an association with spinal arach-
noid cysts and neural tube defects. Several theories have
been proposed
for their etiology.12s Perret
et al proposed
that
these
cysts originated
from arachnoid
faults in the
septum
posticum
of Schwalbe,
which
divides the dorsal

47
CongenitalAbnormalities
371
A
.~~
B
Figure47-18
Arachnoid cyst. (A) Sagittal Tl-weighted
image of a large thoracic arachnoid cyst. (8) AxialT2-weighted
image in same patient.
"Jotecompression of thecal sac.
I
,
subarachnoid
spacein the midline from the cervical to the
lumbaregion.126Tengand Rudner proposed that normal
variationsof intraspinal CSFpressure
lead to cyst forma-
tionthroughdilatation of low-resistance
areas in the
arachnoid.127Fortuna et al proposed
that arachnoid
cysts
arisedueto hypertrophy, proliferation, and dilatation of
arachnoidgranulations.128If the dilatation
was confined by
aresistantdura then an intradural
arachnoid
cyst would
result.whereas a weakened or insufficient
dura would al-
lowherniation,causing an extradural
cyst or meningocele.
Clearly,arachnoid cysts may also be noncongenital
in ori-
ginwithsome cysts forming after a history of trauma.
Still,
thepresenceof familial occurrence
supports
a congenital
originforthese lesions. Histologically, these cysts have no
epitheliallining or an attenuated
layer of arachnoid
cells.
Howintradural arachnoid
cysts communicate
with
the
normal(SF pathways
is unclear
but
a ball valve-like
mechanismhas been postulated
for enlarging
cysts caus-
ingcompression. The fluid contained
in spinal arachnoid
cystsis identical to that found in intracranial
arachnoid
cystsand is similar to CSF in appearance
and chemical
compositionunless hemorrhage
within
the cyst has oc-
curred.Patients present
with signs and symptoms
of a
compressivemyelopathy
similar
to that
seen
in tumor,
spondyliticdisease, or tumor. The onset is often insidious
withslowlyprogressivemyelopathy with or without radic-
ularsymptoms.In one series, 85%of patients
had objective
neurologicalfindings at the time of diagnosis,
including
sensoryloss,spasticity, or motor deficit. Pain was present
in 90%of patients at presentation.
A fluctuating
course
I
Ilk
with exacerbations and remissions may also be seen. Plain
radiographs are usually normal and the diagnosis is made
with a combination of MRIand CTmyelography with de-
layed images. Sometimes it is necessary to tilt the patient's
head up or head down to allow for better filling of these
lesions. Treatment for symptomatic cysts is complete sur-
gical excision.133An exception to this would be patients
with a large arachnoid cyst spanning many levels in whom
a long-segment laminectomy might cause morbidity or in-
stability. In this situation a limited laminectomy with wide
fenestration is usually adequate. Cysts located anterior to
the cord may also be fenestrated instead of excised to pre-
vent cord manipulation and injury. Shunting of the cyst is
not the first treatment
option but may be helpful in the
management of recurrent cysts.
Ependymal cysts (neuroepithelial
cysts) are cysts lined
by a simple columnar or cuboidal to columnar epithelium
with or without cilia.134They are extremely rare with less
than 20 cases reported in the literature in an intraspinal 10-
cation.135These cysts are believed to arise from ectopic
ependymal fragments displaced from the central canal dur-
ing development and can occur potentially anywhere along
the spinal axis. They are intradural in location and often
anterior
and
would
also be classified as a type III
meningeal cyst in the Nabors classification. They are less
likely to be connected to CSFpathways and can be demon-
strated by CTmyelography as an intradural filling defect.
More recently they have been studied by MRIwith the
cysts having a variable appearance on both T1- and 12-
weighted images that often differs from CSFcharacteristics

.
372
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
(perhaps due to secreted proteins from the cyst wall cells).
Patients present with either a slowly progressive myelopa-
thy or sudden deterioration after trauma. At surgery there
is often no plane between the cyst wall and the com-
pressed thecal sac. The surgical goal in these cases is not
total excision but decompression of the cyst and its con-
tents because recurrence of this type of cyst has not been
reported.
.
ExtraduralSpinal Cysts
These cysts are a group of congenital diverticula of either
the spinal meningeal sac, nerve root sheath, or arachnoid.
Although anatomically
these
lesions are truly spinal
meningeal diverticula, the term spinal meningeal cyst (MC)
is more commonly used in the Iiterature.136
.
Extradural Meningeal
Cysts
Extradural meningeal cysts are dural diverticula that may
occur anywhere along the thecal sac and are called sacral
meningoceles when found in the sacral region. They are
classified by Nabors as type I MCsdue to absence of nerve
root fibers in the cyst wall. These lesions are believed to be
related to transmitted hydrostatic pressure of the CSF.They
are most commonly found as enlargements
of the sub-
arachnoid space up to the level of the dorsal root ganglia
and are likely related to congenital defects in the dura at
this location. In the thoracic spine they more commonly
present in adolescents and the younger age of presentation
is thought to be due to the smaller diameter of the thoracic
spine. Patients present with thoracic radicular pain or
paresthesias. Treatment for the symptomatic cyst is surgi-
cal with simple ligation of the ostium usually sufficient for
cure, although in rare cases the cysts reaccumulate and re-
quire treatment by ventriculoperitoneal shunt to lessen the
hydrostatic pressure.
.
Tarlov's Perineural Cysts
Tarlov's perineural cysts (spinal nerve root diverticula) ap-
pear grossly as dilations of the spinal nerve root sleeves at
the dorsal root ganglia. They are classified as type II MCs
by Nabors due to the presence of nerve root fibers in the
cyst wall. These cysts may be multiple and are more com-
mon in the lumbar and sacral regions. Only one quarter
are reported to be symptomatic, usually with radicular
pain. Because these lesions do not have a true pedicle
amenable to closure, treatment has ranged from simple
bony decompression to partial resection with oversewing
of the cyst wall.
.
Extradural Arachnoid Cysts
Arachnoid cysts may also occur in an extradural location.
These cysts are more likely to be familial and associated
with other disorders. An association with extraduralarach-
noid cysts and Scheuermann's kyphosis and a syndromeof
districhiasis (double row of eyelashes) with lowerextrem-
ity lymphedema has been reported. Presentation andclini-
cal management are similar to those for intraduralarach-
noid cysts.
. lateral
or
Anterior
Thoracic
Meningoceles
An intrathoracic
meningocele137.138is to be differentiated
from the posterior meningocele associated withspinal
dysraphism
described
earlier.139-141An intrathoracic
meningocele is a herniation of the dura mater andarach-
noid out of the spinal canal in either a lateral or anterior
direction. The herniation usually occurs into theretro-
pleural space in the region of the posterior mediastinum.
These meningoceles are usually asymptomatic andmay
appear as a possible mediastinal
mass seen on routine
chest radiographs. When symptomatic, the patient may
present with chest or back pain often in a radicularna-
ture secondary
to distortion
of the nearby intercostal
nerves. The diagnosis
is usually
made in the fourth
decade. There is a slight female preponderance (3:2).The
lateral meningocele is the more common of the anom-
alies (9:1) and usually exits through
enlarged neural
foramina. Up to 61% of these lateral meningoceles are
found in association
with Recklinghausen's diseaseor
Marfan's syndrome and this is thought to be due tothe
presence of bony dysplasia and dural ectasia with these
disorders, permitting the development of a meningocele
at the intervertebral
foramen.142When kyphoscoliosisis
present, the lateral meningocele
usually arises on the
apex of the curve on its convex side. Although mostoften
single, there have been numerous reports of bilateralor
multilateral thoracic meningocelesin patients withneu-
rofibromatosis. Anterior thoracic meningoceles aremuch
rarer and not usually found in association with neurofi-
bromatosis.
Instead they are thought
to result froman
embryologicaldefect in the anterior vertebral bodythat
allows herniation
of the dura and arachnoid into the
chest.
Of 100 cases of intrathoracic
meningocele
reported by
Wilkins, the clinical presentation was as follows: 40pa-
tients
were asymptomatic,
30 patients
had chest or back
pain that was often radicular in nature, 24 patients had
symptoms of pulmonary compression or cough, 11patients
were myelopathic, and eight patients presented with scolio-
sis. Delayed images on CTmyelography are most usefulin
establishing
the diagnosis.143 Percutaneous
aspiration orin-

47
Congenital Abnormalities
373
jectionof the cyst is not recommended. If surgery is indi-
cated,treatment is directed toward ligating the meningo-
celepedicle in a watertight fashion, usually via an antero-
lateralapproach.
. Hydrosyringomyelia
Anydiscussion of cystic lesions of the thoracic cord should
includesyrinxes. The terms syringomyelia and hydromyelia
havebeen given to intramedullary
cystic lesions of the
spinalcord(Fig.47-19A,B).Hydromyeliarefers to dilatations
of the central canal that are at least partially lined by
ependymalcells. Syringomyelia refers to all other cavities of
thespinal cord outside of the central canal, which may be
linedby glial cells. The term hydrosyringomyelia has been
suggestedto better describe the pathological findings of
asymmetricalcavitation of the central canal lined by both
ependymaland glial tissue. Williams has proposed a classifi-
cationsystem based on the anatomical abnormality causing
thecavitation.92.144
Syrinxes associated with developmental
abnormalitiesof the hindbrain (Chiari malformations) (73%)
werethe most common followed by other causes (17%)in-
cludingtumor, postarachnoiditis, and trauma.145A critical
distinction,especially when considering therapy, is whether
ornot these cavities communicate with the CSFpathways.
Thesyringomyelia associated with Chiari malformations is
of the communicating type whereas syrinxes associated
with trauma or neoplasm are noncommunicating.
The term ChiariI malformation refers to downward dis-
placement of the cerebellar tonsils greater than 3 mm be-
low the foramen magnum and is associated
with sy-
ringomyelia.146 The Chiari II malformation
seen
in
myelodysplasia is also associated with hydrosyringomyelia.
Several theories have been proposed regarding the patho-
physiology of the syrinx. Gardner put forth the hydrody-
namic theory where failure of the embryonic posterior
medullary velum to perforate trapped spinal fluid and pro-
duces a water hammer pulse pushing CSFfrom the fourth
ventricle into the upper end of the cervical canal.68The
problem with this theory is that it is often impossible to
demonstrate
a communication
between the spinal cord
cavity and the floor of the fourth ventricle.147Williams
studied the problem of hydrosyringomyelia extensivelyand
proposed a theory based on the disassociation between
intracranial
and intraspinal
CSF pressures. By directly
measuring both the intraspinal and intracranial compart-
ments, he noted that when a patient coughs or strains the
intracranial and intraspinal CSFpressures both rise in tan-
dem. The spinal compartment,
however, dissipates the
pressure more rapidly leaving a brief period of time when
there is net downward pressure into the central canal. Over
time, this is the driving force for the formation of the
syrinx. Patients usually have a slow insidious clinical
presentation.
The classic suspended
sensory loss in a
B
A
Figure 47-19
Hydrosyringomyelia.(A) Axial and (B) sagittal view of Tl-
weighted magnetic resonance image of the typical appearance of asyrinx.

374
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar
Spine
capelike distribution is often hard to demonstrate. Asym-
metric limb sensory or motor changes are most common as
is spasticity in one or both legs. Bowel and bladder symp-
toms may be present. It is not uncommon for patients to
present with scoliosis related to muscular imbalance re-
lated to loss of paraspinal musculature.148.149MRI is the
study of choice to evaluate both the syrinx and the hind-
brain hernia if it is present. Treatment of the syrinx is sur-
gica1.31.150
Prior to any other considerations for treatment,
raised intracranial pressure must either be excluded or
shunted if present. Ifa hindbrain hernia is present, the pos-
terior fossa should be decompressed. These maneuvers are
usually sufficient to arrest or decrease the syrinx. Attempt-
ing to drain the syrinx with a syringosubarachnoid shunt is
often problematic because the pressure outside of the cord
is often higher than that within the syrinx. Draining the sy-
rinx into a low pressure area such as the pleural space is
more effective but in large multiloculated
syrinxes it is
possible that not all of the syrinx will be drained.
.
Terminal Syringohydromyelia
Aterminal syrinx is a cystic dilatation of the lower third of
the spinal cord usually occurring cephalad to other mani-
festations of 050.151It is present in at least a third of 050
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48
Disk Disease of the Thoracic
and Thoracolumbar Spine
Nicholas Post and Anthony K. Frempong-Boadu
.
Epidemiology
.
Pathophysiology
.
ClinicalEvaluation
ThoracicRadiculopathy
ThoracicMyelopathy
.
Differential Diagnosis
.
Radiological Evaluation
.
Treatment
.
Conclusion
Thoracic disk herniation is an uncommon entity that may
occur in any age group and can be difficult to diagnose.I-4
The clinical diagnosis is difficult because the symptoms of
thoracic disk disease vary based on the anatomicalloca-
tion of the herniated disk materia1.1.5-9Lateral thoracic
disk herniations present with radicular symptomatology.
In contrast, central thoracic disk herniations present with
either or both thoracic myelopathy and spinal cord syn-
dromes.s.1o
Radicular symptoms are caused by nerve root compres-
sion by laterally herniated disk material or by foraminal
stenosis caused by osteophyte
formation. Myelopathic
symptoms are caused by spinal cord dysfunction due to
extradural compression of the spinal cord caused by herni-
ated disk material, osteophyte formation, or a combination
of both.s.8.11
This chapter describes the signs, symptoms, and contem-
porary management of symptomatic thoracic disk disease.
. Epidemiology
Thoracic disk disease is most common in the middle to late
fifties, although rare cases have been reported in the pedi-
atric population.12-14There is slight male to female predom-
inance (1.5:1).The incidence of symptomatically significant
thoracic disk herniations is low. It has been estimated at
one per million per year, underscoring the rarity of this
378
disease process. It may occur after spinal trauma.2 However,
the onset
is more likely to be insidious.
Haley and Perry
showed
that
11% of unselected
autopsies
revealed pro-
truded thoracic disks.2,15
. Pathophysiology
Thethoracicspineis composedoftwo regionswithdistinct
biomechanical properties. The upper thoracic spine-Tl to
T9-is considered the fixed thoracic spine. The biomechani-
cal properties of the upper thoracic spine are governedby
the rib cage, which arises dorsally at the costotransverse
articulation and travels ventrally to join the sternum.The
coronal orientation of the facet joints in the upper "fixed"
thoracic spine provide mechanical resistance to anterior
translation.16Theseanatomical aspects of the uppertho-
racic spine contribute to its structural
rigidity, limiting
movement.17.18
The lower thoracic spine extends from no to T12andis
much more mobile. This lower segment of the thoracic
spine,termedthe transitionalspine,bridgestheuppertho-
racic spine to the lumbar spine both structurally andfunc-
tionally. The vertebral bodies of the thoracic spine increase
in size, and the facets joints assume a more sagittalorienta-
tion as they become more structurally similar to the lumbar
spine.Theno to L1ribs are "free"and lackventralsternal
fixation. This transitional
area
endures
much of the

48
DiskDisease
379
mechanicalstress in the thoracic spine.19Anatomical factors
affectingthe biomechanical stresses at the thoracolumbar
junction include the transition from the kyphotic thoracic
spineto the lordotic lumbar spine, as well as the change in
thefacets from a coronal to a sagittal orientation.17.19These
uniquebiomechanical properties contribute significantly to
thedegenerative pathology seen in this region.1S
Thusthe rarity of symptomatic thoracic disk herniation is
secondaryto the relative immobility of the thoracic spine.
However,as the mobility of the thoracic spine increases
fromrostral to caudal it becomes progressively more sus-
ceptibleto disk degeneration and herniation. In fact, 75%of
symptomaticthoracic disk herniations occur below the T8
level,with herniations at the T11-T12 level being the most
common.2.7.S
Thepathophysiology of thoracic disk degeneration paral-
lelsthat in the cervical or lumbar spine, and the mecha-
nismsare similar. The radiographic changes and symptoms
associatedwith nontraumatic thoracic disk disease are due
tothe expected degenerative changes observed in the aged
population.20Thoracic disks, like cervical and lumbar disks,
arecomposed of the gel-like nucleus pulposus surrounded
by the fibrous anulus fibrosus. The nucleus pulposus is
madeup of proteoglycan units electrostatically bound to
watermolecules embedded in a type 2 collagen superstruc-
ture.It allows for dynamic compressibility because of its
highwater content (-85% at birth). This water content
decreaseswith age, decreasing the ability of the nucleus to
resist compressive
forces.s.21
Theanulus fibrosus is made up of collagen formed in a
latticework.It is the peripheral supporting structure of the
diskfirmly anchoring it to the cartilaginous end plates of
thevertebrae above and below. The anulus fibrosus resists
thetorsional and tensile stresses of axial loading. The func-
tionalvertebra-disk-vertebra
motor unit is efficient in its
abilityto withstand axial loading because of the shock-ab-
sorbingcharacteristic of the combined anulus and nucleus.
Thedisk acts like a viscoelastic shock absorbing structure.21
Withage the disk undergoes a process of degeneration and
collapse. These degenerative
changes are heralded
by
changesin the glycosaminoglycan ratio within the disk and
bydecreases in both the proteoglycan and water content.
Whichnegatively affect the functional ability of the disk
withdehydration and loss of compressibility, the disk/inter-
spaceheight diminishes. This leads to laxity of the anulus
anddecreased ability ofthe disk to resist tensile forces.2o-22
Theseage-related osteoarthritic changes are responsible for
thedegeneration of the intervertebral disk. Osteoarthritic
changesalso account for osteophyte formation. This occurs
secondaryto the tilting of the vertebral bodies as the disk
degeneratesand loses height and function stimulating aber-
rantboneformationand remodeling.21
. ClinicalEvaluation
Thereis wide variation in the clinical presentation of tho-
racicdisk herniation. The signs and symptoms depend on
thelocationof the herniation, size of the lesion, duration of
compression,and relative size of the bony canal. In general.
the condition is dynamic and the symptoms are slowly pro-
gressive. The clinical presentation can be broadly divided
into two groups: thoracic radiculopathy
and thoracic
myelopathy.2.3.10.23.24
Thoracic Radiculopathy
Thoracic radiculopathy is caused by lateral thoracic disk
herniations. The hallmark of a laterally herniated thoracic
disk is radicular pain. The location of pain depends on the
level of the herniation. Lateralherniations are less common
than central herniations and cause compression of the tho-
racic nerve roots, rather than the spinal cord.Thusthere are
no signs of spinal cord dysfunction. Patients often report
burning or lancinating pain, which radiates laterallyand an-
teriorly in a beltlike fashion. The pain is dermatomal in na-
ture and is rarely bilateral. Ifthe pain is left-sided midtho-
racic, it can be easily confused with myocardial ischemia
pain. Some patients also report severe localized tenderness
with hyperpathic sensations that can be confused with her-
petic
pain.5.S.25.26
Back pain is frequently the first symptom. Because the
thoracic nerve roots innervate the intercostal muscles,there
is usually no discernible motor deficit. On examination
there may be dermatomal sensory loss. Careful sensory ex-
amination is necessary to localize the level of pathology.26
Thoracic Myelopathy
Centrally herniated thoracic disks cause thoracic myelopa-
thy. The majority of thoracic disk herniations occur in the
midline. Symptoms are caused by spinal cord dysfunction
secondary to extradural compression of the spinal cord by
herniated disk material, osteophytes, or a combination of
both.2
Most patients have long-standing symptoms with insidi-
ous onset and slow progression over a period of months to
years. Sensory loss and paresthesias on the trunk and legs
are frequent early complaints. These symptoms progress to
gait unsteadiness, spasticity, sexual dysfunction, and bowel
and bladder dysfunction. Lower extremity weakness is a
late finding.2.5.27
Physicalexamination usually shows a diminished sensory
level to pin prick one or two spinal segments below the
level of the disk herniation. Symptoms are usuallybilateral.
Patients will frequently have increased lower extremity
deep tendon reflexes with normal upper extremity reflexes
and motor/sensory function. Diminished lower extremity
joint position sense is also a common finding.
Surgery is indicated in patients with symptomatic tho-
racic disk herniations to both treat and prevent the sequelae
of thoracic spinal cord compression.2.24
.
DifferentialDiagnosis
Thoracic myelopathy is often confused with
cervical
myelopathy, but there are no concomitant upper extremity
motor/sensory
or deep
tendon
reflex
symptoms
or

380
Thoracic and Thoracolumbar
Spine: Pathology of the Thoracic and Thoracolumbar
Spine
findings.28.29Painless thoracic myelopathy has historically
been confused with other neurological syndromes, such as
multiple sclerosis, but careful physical exam and radiologi-
cal evaluation can easily distinguish the two.30
When a patient presents with the onset of pure thoracic
myelopathy a compressive
lesion must be ruled out.
The most common cause of dysfunction in younger patients
is an intradural tumor such as a meningioma or neurofi-
broma.3! Neurofibromas, which usually originate from the
sensory portion of a nerve root, may mimic a thoracic disk
by compressing the nerve root producing pain and radicular
sensory loss. Myelopathy occurs as these lesions grow and
eventually compress the spinal cord. Magnetic resonance
imaging (MRI) can readily distinguish intradural tumors
from thoracic disk herniations.30
Intramedullary tumors such as astrocytomas and ependy-
momas and syringomyelia can also present with thoracic
myelopathy. They are frequently associated with dyses-
thetic pain but signs and symptoms may otherwise be in-
distinguishable from other causes of thoracic myelopathy.
MRIalso readily distinguishes intramedullary tumors and
syrinx formation from thoracic disk herniations.3o.3!
.
Radiological Evaluation
Patients should undergo complete radiological workup in-
cluding plain films and MRI.Myelography and diskography
are indicated in unclear cases. Patients must have a clear,
well-defined neurological deficit with confirmatory radi-
ographic studies before any attempt should be made at op-
erative management,2.8
References
1.
Lesoin F. Rousseaux
M, Autricque
A. et al. Thoracic
disk herniations:
evolution
in the approach
and indications.
Acta Neurochir
(Wien)
1986;80:30-34
2.
Stillerman
CB.Weiss MH. Management
of thoracic
disk disease.
Clin
Neurosurg
1992;38:325-352
3.
Wilke A. Wolf U. Lageard P, et al. Thoracic disk herniation:
a diagnos-
tic challenge.
Man Ther 2000;5: 181-184
4.
Wood KB,Blair JM. Aepple DM. et al. The natural
history of asympto-
matic thoracic disk herniations.
Spine 1997;22:525-530
5.
Benjamin
V.Diagnosis and management
ofthoracic
disk disease.
Clin
Neurosurg
1983;30:577-605
6.
Carson J.Gumpert J.Jefferson A.Diagnosisand treatment of thoracic
intervertebral
disk
protrusions.
J Neurol
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Psychiatry
1971 ;34:68-77
7.
Dickman CA,Theodore
N, HurlbertJR.
et al. Thoracic disk.J Neurosurg
1996:85:187-188
8.
Dietze DD Jr, Fessler RG.Thoracic disk herniations.
Neurosurg
Clin N
Am 1993;4:75-90
9.
Le Roux PD, Haglund
MM, Harris AB. Thoracic
disk disease:
experi-
ence
with
the transpedicular
approach
in twenty
consecutive
pa-
tients.
Neurosurgery
1993;33:58-66
10.
Tokuhashi
Y, Matsuzaki
H, Uematsu
Y. et al. Symptoms
of thora-
columbar
junction
disk herniation.
Spine 2001 ;26:E512-E518
11.
Stillerman
CB.Chen TC. Couldwell
WT, et al. Experience
in the surgi-
cal management
of 82 symptomatic
herniated
thoracic
disks and re-
view ofthe
Iiterature.J
Neurosurg
1998:88:623-633
12.
Dhammi
IK, Arora A, Monga J. Calcified thoracic
intervertebral
disk
at two levels as a cause
of mid-back
pain in a child:
a case report.
J Orthop Sci 2002;7:587-589
.
Treatment
Patients with progressive thoracic myelopathyrequire
thoracic spinal cord decompression to prevent progression
of symptoms. Patients with severe thoracic radicularpain
that have failed conservative
management
should also have
thoracic nerve root decompression.
The operative management
of symptomatic thoracic
and thoracolumbar disk disease has evolvedin recent
years. Laminectomy and disk excision are no longer
performed because of the significant risk of neurological
deterioration.32 There are several anterior and posterolat-
eral approachesthat havebeen developedtodealwiththis
very interesting surgical problem.I.5.9.25.33-40
Operativeman-
agement of thoracic and thoracolumbar
disk diseaseand
the various anterior and posterolateral surgicalapproaches
for this problem are discussed in detail throughout this
book.
. Conclusion
Thoracicdisk disease is an uncommondiseaseentitythat
affects mostly the aged population. It can be difficultto
diagnose; the clinician can be easily confused as to the
cause of the patient's complaints. However, with careful
history and physical examination and proper radiological
workup, it can be readily distinguished from other disease
entities with seemingly similar presentations. Withcare-
ful preoperative
evaluation and thoughtful selectionof
surgical approach, it can be a very satisfyingdisease
entity to treat.
13.
Heithoff KB.Gundry CR. Burton CV.et al. Juvenile
diskogenic disease.
Spine 1994;19:335-340
14.
Kozlowski
K. Anterior
intervertebral
disk
herniations
in children:
unrecognised
chronic
trauma
to
the
spine.
Australas Radiol
1979;23:67-71
15.
Haley J.Perry J.Protrusions
of intervertebral
disks: the study oftheir
distribution,
characteristics
and effects on the nervous system. Am]
Surg 1950:80:394-404
16.
Maiman
D. Pintar
F, Groff M. et al. Concepts
and mechanisms ofbio.
mechanics.
In: Winn
H, ed. Youmans
Neurological
Surgery. Vol4.
Philadelphia:
WB Saunders:
2004:4181-4201
17.
Frempong-Boadu
A. Guiot B. Anatomy
and biomechanics
of the tho-
racic spine.
In: Batjer
H, Loftus
C, eds.
Textbook
of Neurological
Surgery. Vol 2. Philadelphia:
Lippincott-Raven;
2003:1544-1551
18.
Resnick DK. Weller SJ, Benzel EC. Biomechanics
of the thoracolumbar
spine. Neurosurg
Clin N Am 1997:8:455-469
19.
Pal GP, Routal RV.Mechanism
of change
in the orientation
of thear-
ticular
process of the zygapophyseal
joint at the thoracolumbar junc-
tion.J Anat 1999;195(Pt
2):199-209
20.
Goh S. Tan C. Price RI, et al. Influence
of age and gender on thoracic
vertebral body shape and disk degeneration: an MRinvestigationof
169 cases. J Anat 2000:197(Pt
4):647-657
21.
Koeller W. Meier W. Hartmann
F. Biomechanical
properties
of human
intervertebral
disks subjected
to axial dynamic
compression:
a com-
parison
of lumbar
and thoracic
disks. Spine 1984;9:725-733
22.
Ghosh
P. Taylor
TK, Braund
KG, et al. The collagenous
and non.
collagenous
protein
of the
canine
intervertebral
disk and their
variation
with
age.
spinal
level
and
breed.
Gerontology
1976:22:124-134

48
DiskDisease
381
23. Mulier S, Debois V.Thoracic disk herniations:
transthoracic.
lateral. or
posterolateral
approach?
A review. Surg NeuroI1998;49:599-608
24. O'Leary PF.Camins MB. Polifroni NV.et al. Thoracic disk disease:
clini-
cal manifestations
and surgical
treatment.
Bull Hosp Jt Dis Orthop
Inst 1984;44:27-40
25. Delfini R, Di Lorenzo N, Ciappetta
p. et al. Surgical
treatment
of tho-
racic disk herniation:
a reappraisal
of Larson's
lateral
extra cavitary
approach. Surg NeuroI1996;45:517-522
26. O'Connor RC.Andary MT. Russo RB, et al. Thoracic radiculopathy.
Phys
Med Rehabil Clin N Am 2002;13:623-644
27. Campbell E. Kite WC Jr. Whitfield
RD.The thoracic
herniated
interver-
tebral disk syndrome.J
Neurosurg
1957;14:61-67
28. Alberico AM. Sahni KS. Hall JAJr, et al. High thoracic
disk herniation.
Neurosurgery
1986;19:449-451
29. Arana E. Marti-Bonmati
L. Molla E. et al. Upper thoracic-spine
disk
degeneration
in
patients
with
cervical
pain.
Skeletal
Radiol
2004;33:29-33
30. Blumenkopf
B. Thoracic
intervertebral
disk herniations:
diagnostic
value of magnetic
resonance
imaging.
Neurosurgery
1988;23:36-40
31. Bose B.Thoracic extruded
disk mimicking
spinal cord tumor. Spine J
2003;3:82-86
32. Fessler RG,Sturgill M. Review: complications
of surgery
for thoracic
disk disease. Surg NeuroI1998;49:609-618
33.
Coleman RJ,Hamlyn PJ, Butler P. Anterior
spinal surgery
for multiple
thoracic disk herniations.
BrJ Neurosurg
1990;4:541-543
34.
Dinh DH. Tompkins J, Clark SB.Transcostovertebral
approach
for tho-
racic disk herniations. JNeurosurg Spine 2001 ;94:38-44
35.
el-Kalliny
M. Tew JM Jr, van Loveren H. et al. Surgical
approaches
to
thoracic
disk herniations.
Acta Neurochir (Wien) 1991 ;111:22-32
36.
Frempong-Boadu
A, Fessler R. Lessons in the techniques
of surgical
exposures
of the thoracic
and lumbar spine: anterior
approaches.
In:
Krisht A. ed. Contemporary
Neurosurgery.
Vol 22. Hagerstown.
MD:
Lippincott Williams & Wilkins: 2000
37.
Frempong-Boadu
A. Fessler R. Lessons in the techniques
of surgical
exposures
of the thoracic
and lumbar spine: posterior
approaches.
In:
Krisht A. ed. Contemporary
Neurosurgery.
Vol 22. Hagerstown.
MD:
Lippincott Williams & Wilkins;
2000
38.
Korovessis
PG. Stamatakis
MV, Baikousis A, et al. Transthoracic
disk
excision
with
interbody
fusion:
12 patients
with symptomatic
disk
herniation
followed
for
2-8
years.
Acta
Orthop
Scand
Suppl
1997;275:12-16
39.
Maiman
DJ.Larson SJ. Luck E, et al. Lateral extracavitary
approach
to
the spine
for thoracic
disk
herniation:
report
of 23 cases. Neuro-
surgery
1984; 14: 178-182
40.
Stillerman
CB. Chen TC, Day JD. et al. The transfacet
pedicle-sparing
approach
for thoracic
disk removal:
cadaveric
morphometric
analysis
and preliminary
clinical experience.J
Neurosurg
1995;83:971-976

49
Tumorsof the Thoracolumbar Spine
AshokModha,
EhudMendel, and
Bernard H. Guiot
. Symptoms
. RadiologicalEvaluation
. MedicalEvaluation
Biopsy
LaboratoryEvaluation
Staging
Neoplasiaofthe spineis a regrettablycommonproblem.As
theincidence of cancer in general rises and the prognosis
improveswith newer treatments, it can be anticipated that
thescopeof spinal involvement will increase with time.
Spinaltumors may be primary or metastatic in origin.
Primarytumors are rare and account for -5% of all new
bone tumors. Benign tumors are more frequent in the
youngerage groups, whereas malignant lesions occur in
adultpopulations, where they account for 80%of tumors
seeninthe spine (Tables 49-1, 49-2),1.2
Primarytumors can be classified on the basis of their cell
oforigin(Table49-3). They may arise from cells directly in-
volvedin the production and remodeling of bone, including
osteoblasts,chondroblasts, fibroblasts, and osteoclasts. AI-
Table49-1
TumorsbyAgeGroups
Young
«2nd Decade)
Middle Age
Old
(2nd to 5th Decades)
(> 5th Decade)
. Treatment
. Prognosis
.
Differential Diagnosis
Benign Tumors
MalignantTumors
MetastaticTumors
ternatively, they may arise from cells found in or near bone
but not directly involved in the production of bone. These
include tumors derived from bone marrow, notochordal
remnants, blood vessels, and the nerve sheath.
Metastatic
tumors
of the spine are 40 times more
common than primary tumors. Fifty to 70%of patients with
carcinoma will develop bony metastases during the course
of their illness, the spine being the most common site of
skeletal disease.3 Indeed, there are an estimated 800,000
new cases of spinal metastases
diagnosed in the United
States each year.1.2These metastases are more likely to be
found in the thoracic spine and thoracolumbar junction and
originate in the breast, lung, prostate, and hematopoietic
system (Table49-3).
Table 49-2
Age, Location of Tumor, and Histopathology
383
Osteoidosteoma
Osteoid osteoma
Chondrosarcoma
Osteoblastoma
Osteochondroma
Plasmacytoma
Osteochondroma
Hemangioma
Multiple myeloma
Aneurysmalbone cyst
Giant celltumor
Lymphoma
Eosinophilicgranuloma
Osteosarcoma
Chordoma
Ewing'ssarcoma
Ewing's sarcoma
Paraspinal soft
tissue tumors
Lymphoma
Metastatic
tumors
Paraspinal soft
tissue tumors
Metastatic tumors
Age
Vertebral
location
Histopathology
< Second decade
Posterior elements
Benign
> Second decade
Anterior colunm (VB)
Malignant
> Fifth decade
Anterior colunm
Metastatic or
(VBand pedicles)
multiple myeloma

384
Thoracic and Thoracolumbar Spine: Pathology of the Thoracic and Thoracolumbar Spine
.
Symptoms
Patients with tumors of the thoracic and thoracolumbar
spine become symptomatic for a variety of reasons. The tu-
mor within the vertebral body may cause expansion of the
cortex,resulting in significant pain. The destructive process
mayresult in pathological fractures and the onset of spinal
instability.The tumor may also manifest itself through the
compression of the epidural venous plexus with resulting
spinal cord vasogenic edema. hemorrhage, demyelination.
and ischemia.There may be compression of the spinal cord,
adjacent nerve roots, or paravertebral structures as a result
of tumor outgrowth. Finally, direct invasion of the nerve
roots can occur.3
Pain and weakness are the most common presenting
complaints.4Painoccurs in 95%of patients and is described
as progressive and unrelenting. It is not related to activity
and is neither relieved with rest nor with recumbence. In-
deed, night pain is characteristic of tumoral invasion of the
spine. Radicular pain also occurs. It is present in 28%of pa-
tients and is the result of irritation, direct compression, or
infiltration of nerve root.s
Weakness occurs in -40% of people. It is more likely in
patients who harbor malignant lesions,where the incidence
is as high as 55%.3It may, however, not become apparent
until months or years after the onset of pain.The symptoms
are part of a myelopathic process, resulting from the com-
pression of the spinal cord in the narrowed thoracic spinal
canal. The clinical manifestations include spasticity, gait
disturbance. paraparesis or paraplegia. and loss of sensa-
tion. Temperature, position, and vibratory sensation are lost
early. whereas
light touch is usually the last sensory modal-
ity to be lost. Patients may also develop bowel and bladder
incontinence
as well as autonomic
dysfunction
such as or-
thostatic
hypotension
and impotence.
Constitutional
symptoms
such as weight
loss, fever,fa-
tigue, anorexia,
cachexia.
and constipation
are features of
spinal neoplasia.
.
Radiological Evaluation
There are several general rules that apply to the radi-
ographicappearanceofspinetumors.Slow-growingtumors
have clearly marginated borders. A well-defined sclerotic
marginis identified.Tumorsthat advancesomewhatmore
rapidly may have lost their sclerotic margins and instead
have ragged edges. They may also be surrounded bya
pseudocapsule. More aggressive tumors that grow rapidly
produce a moth-eaten appearance or permeative patternof
bone destruction.6 They may transgress tissue planes,al-
though intervertebral disks. cortical bone, fascial planes,
and ligaments act as barriers to tumor progression. Benign
lesions are more likely to be found in the posterior ele-
ments (Table 49-4). The majority of malignant tumors,
both primary and metastatic, originate anteriorly, involving
the vertebral body and one or both pedicles. Metastasesin-
volve the vertebral body and pedicles if spread hematoge-
nously. Direct invasion by other tumors may involveany
part of the vertebra and can also lead to extension through
the intervertebral foramina into the vertebral canal.
Table 49-3
Primary Tumors of the Spine
Origin
Benign
Malignant
Bony tumors
Osteoblast
Osteoma
Osteosarcoma
Osteoid osteoma
Osteoblastoma
Cartilaginous tumors
Chondroblast
Chondroma
Chondrosarcoma
Osteochondroma
Chondroblastoma
Giant cell tumors
Osteoclast
Connective tissue
Fibroblasts
Fibroma
Fibrosarcoma
tumors
Adipocytes
Lipoma
Liposarcoma
Malignant
rnesenchymoma
Vascular tumors
Blood vessel
Hemangioma
Angiosarcoma
Glomus tumor
Hemangiopericytoma
Bone marrow
Plasmacytoma
Multiple
myeloma
tumors
Ewing's sarcoma
Malignant
lymphoma
Nerve sheath tumors
Schwann cell
Schwannoma
Neurofibroma
Other
Chordoma
Aneurysmal
bone cyst
Eosinophilic
granuloma

Table49-4
Vertebral Involvement in Various Types of Spinal
Tumors
Anterior Elements
Posterior Elements
Hemaniomaoma
Eosinophilicgranuloma
Giantcell tumor
Osteochondroma
Chondrosarcoma
Osteosarcoma
Ewing'ssarcoma
Plasmacytoma
Multiple myeloma
Lymphoma
Chordoma
Osteoid osteoma
Osteoblastoma
Osteochondroma
Aneurysmalbone cyst
Chondrosarcoma
Plainradiography may reveal osteolytic or osteoblastic
bonylesionsdepending on the type of tumor. Bonedestruc-
tionis usually not apparent until 30 to 50%of trabecular
bonehas been destroyed.3 Vertebral body collapse may oc-
curfollowing extensive
bone erosion. Disk height is usually
maintained, even after
profound
vertebral
damage.
The
"winkingowl" sign on an anteroposterior
view denotes the
unilateral loss of a pedicle ring due to tumor invasion from
thevertebral body. Soft tissue calcifications
or a soft tissue
massmay also be apparent.
Scoliosis
may be present,
al-
thoughthe typical findings of vertebral
rotation
and wedg-
ingassociated with idiopathic
scoliosis are not characteris-
tically found with neoplastic curves.s
Radioisotope(99m-technetium) bone scans are sensitive
teststhat may be helpful in detecting the presence of os-
teoblasticlesions as small as 2 mm. Unfortunately, the test
isnotspecificand false-positive results may be obtained in
thepresenceof infection, fracture, or inflammation. Afalse-
negativescan may also occur, mainly when the spine is
seededwith multiple myeloma, solitary plasmacytoma,
chordoma,or metastases from lung cancer or renal cell car-
cinoma.7Thisphenomenon occursas a result of the rapid
growthof the lesion and the absence of reactive bone for-
mationrequiredfordetectionwithisotopescans.
Computedtomographic (er) scanning is a very important
toolinthe evaluationofspinaltumors.Itis highlysensitive
toalterations in bone mineralization and can delineate the
extentof bony disease. It is useful in identifying the pres-
enceof bone fragments within the canal in pathological
fractures,and when coupled with myelography, can also be
usedin the diagnosis of cord compression. Additionally,soft
tissuemasses may be demonstrated. er is also very impor-
tantforsurgicalstaging and planning. The axial images may
besupplemented with sagittal and three-dimensional
re-
constructionto help in the planning of stabilization and in-
strumentationprocedures. The major disadvantage of er is
the need for myelography to establish the presence of
spinalcord compression. This invasive procedure may not
revealthe existence of a noncontiguous second lesion if
thereisacompleteblockelsewhereinthe spine.
49
Tumors of the Thoracolumbar Spine
385
Magnetic resonance imaging (MRI)is very useful in the
diagnosis and treatment planning of tumors of the spine
and serves as the radiological gold standard.8 MRIprovides
excellent soft tissue detail and can also substitute for CT
myelography. Tumor boundaries and spinal cord compres-
sion are easily appreciated. Images can be obtained in all
three dimensions to improve visual-spatial resolution of
the disease process. Tumor,infection, and fracture are usu-
ally easy to distinguish on MRI.The contrast agent, gadolin-
ium diethylenetriamine pentaacetic acid (GdDTPA)may as-
sist
in
enhancing
some
tumors.
MRI also
detects
significantly more patients with multiple sites of cord com-
pression than myelography.8-loThere are, however,certain
limitations that must be recognized. Bonydetail is not well
visualized
on MRI. Compression
fractures may cause
changes that
simulate tumor
on MRIY Flare reaction
around some benign tumors may give the impression that a
tumor is malignant and invasive with a large amount of soft
tissue involvement.1.12.13Finally, patients who have ferro-
magnetic prostheses may not qualify for this test.
Other studies should be considered in the workup of
spinal tumors. Angiography can be a useful tool in demon-
strating
the anterior
spinal artery
and the artery of
Adamkiewicz for surgical planning. It may confirm the need
for embolization of vascular tumors preoperatively.14Single
photon emission er (SPEer) imaging of the thoracolumbar
spine is useful in determining the precise anatomicalloca-
tion of vertebral abnormalities.ls This test should be consid-
ered in patients who have:
1.
a positive bone scan with no anomalies in the spine
2.
back pain but a normal bone scan
3.
a new abnormality
on bone scan with no typical
metastatic spread in the rest of the skeleton
Finally,in addition to the aforementioned radiological as-
sessments, mammography, bone scan, and CTof the chest
and abdomen are required.
.
Medical Evaluation
Biopsy
When a lesion is diagnosed in the spine, a biopsy is essen-
tial. Soft tissue or lytic areas are the best sites for biopsy.16
Contamination of other tissues must be avoided.3er or flu-
oroscopically guided needle biopsies are accurate, simple,
and cost-effective procedures, which yield tissue sufficient
for diagnosis in -75% of cases.17Incisional biopsy may be
required and is preferred over excisional techniques when
the diagnosis is unknown. Anterior lesions require inci-
sional or needle-biopsy techniques for sampling. Posteriorly
located lesions may be more suitable for excisional biopsy.
Frozen sections should be obtained at the time of biopsy to
ensure that adequate sample for definitive diagnosis has
been obtained. Cytologic specimens can undergo histo-
chemical and immunocytochemical procedures for diagno-
sis. All biopsy specimens must also be sent for culture to
rule out osteomyelitis.