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

892
Peripheral Nerve: Pathology of the BrachialPlexus
especially in the acute setting. Nerve conduction studies,
both sensory and motor, are useful during and after the
first week following an injury to distinguish neurapraxic
from axonotmetic and neurotmetic grades. The hallmark
of a neurapraxic injury is nerve conduction slowing or
a complete block along a segment of nerve. The absence
of a nerve conduction
response
in a distal nerve seg-
ment indicates a loss ofaxons
due to either an axono-
tmetic
or neurotmetic
grade
of injury.7 Serial nerve
conduction studies show a progressive diminution in the
amplttude
of the response
after
48 to 72 hours
as
Wallerian degeneration
of the axons occurs.8 Two to
3 weeks following an axonotmetic or neurotmetic grade
of injury, the EMGbecomes abnormal. Spontaneous ac-
tivity, including fibrillations, fasciculations, and positive
sharp waves, develops in the affected muscles.9 The EMG
following a neurapraxic
injury usually remains normal
and can be used to distinguish
a neurapraxic
from the
more severe axonotmetic
and neurotmetic
grades of
injury.
.
RadiologicalEvaluation
Recent advances in MRI using custom designed phase array
coils have resulted
in MR neurographic
(MRN) imagesof
both normal and abnormal peripheral nerves with im.
proved resolution.IO.1IIn addition, conventional MRI cande.
tect signal changes in denervated muscle earlier thanEMG
abnormalities are usually detected.12MRInerve and muscle'I
.
changes were found to be reversible when recovery offunc.
tion occurred as a result of reinnervation.
. Case History: Part III
Clinical
and electrodiagnostic
examinations
at 4 and6
months following the injury and initial surgical repair
showed no evidence of muscle reinnervation.
MRN per.
formed at 6 months showed persistent increased signalin
the right peroneal nerve at and distal to the site of trau.
matic injury and surgical repair on both T2 and STIR
se.
quence images (Fig. 120-58).
Denervated musclesdis.
Figure
120-5
(A) Intraoperative
photograph
atthetime
of the
second
surgical
repair
of the
tibial
and peroneal
nerves. The tibial nerve (two arrowheads)
has beendis.
sected
from the peroneal
nerve (curved
arrow) and anin.
ternal neurolysis of the peroneal
nerve was performed.
The scarred medial component
of the peroneal nervehas
been
resected
and two sural nerve
grafts
(left, doublear.
rows)
placed
to bridge
the
gap.
Several
intact fascicles
(right, single arrows) can be seen in the lateral component
of the peronealnerve,which continue on into the superfi-
cial peroneal nerve. (B-D)
Coronal T2-weighted magnetic
resonanceimagesof the lower extremity (1.5Tesla
Signa,
GE,Milwaukee, WI; custom phased array coils;fast spin
echo
with
fat
suppression
TR 4600-5000
msec, 1£
90-100
msec).
In all figures,
proximal
is to the topofthe
page and the injury/graft
site is marked by the arrow.The
tibial nerve (small arrowhead)
is to the right. (B) Animage
obtained at 6 months following
the initial
surgical
repair.
Note that
the peroneal
nerve distal to the repair siteis
much higher in signal intensity than the tibial nerveand
proximal
peroneal
nerve
(above
the
arrow). (e) At
8 months
following
the second surgery, the signalinthe
distal peroneal
nerve has begun to decrease.
(D) At16
months,
the signal
in the distal peroneal
nerve hasre-
turned to normal. Note how the nerve signal remainsin.
creasedat the surgicalrepairandsuralnervegraftsite.

120
TraumaticPeripheralNerve Injuries
893
playedincreased signal on T2 and STIRsequence MRI
images.
Thedecision making process in exploring
either a closed
traumatic or previously
repaired
peripheral
nerve injury is
morecomplex (Fig. 120-3).
Important
considerations
in-
cludethe fact that muscles should be reinnervated within 2
yearsfollowinga traumatic nerve injury if recoveryof useful
motorfunction is to occur. Beyond this point in time, dener-
vatedmusclesundergo irreversible atrophy and replacement
withfat.Therefore, it is necessary to time a surgical explo-
rationso that a successful nerve repair results in muscle rein-
nervation within
2 years of the injury. By 4 months,
pure
neurapraxicinjuries should have recovered. Therefore, in the
absenceof clinical or electrodiagnostic
evidence
of muscle
innervation,a surgical exploration
using intraoperative
elec-
trophysiologicalstimulation
and recording techniques should
beperformed to determine
whether
axonal regeneration
is
occurringacross the damaged nerve segment.
. CaseHistory: Part IV
Asecond surgical exploration
was performed
8 months fol-
lowingthe initial injury and surgical repair due to the lack of
functionalrecovery as assessed clinically and electrodiagnos-
tically.Intraoperatively,
both the tibial and peroneal nerves
wereextremely scarred at the injury/repair site. Electrical
stimulation of the tibial nerve elicited vigorous contraction of
thecalf muscles. Stimulation
of the peroneal
nerve elicited
nocontraction
of either foot dorsiflexor
or everter muscles
(Fig.120-6).
Internal
neurolysis
of the peroneal
nerve re-
vealedits medial portion to be scarred and no nerve conduc-
tion response or nerve action potential (NAP) could be
recordedacross this segment. The lateral most portion of the
nervecontained intact nerve fascicles that coursed distally
intothe superficial branch of the peroneal nerve. The medial
scarred portion
of the
peroneal
nerve
was excised
until
Figure120-6
Intraoperative
photograph
at the time of the second
surgicalrepair following an external neurolysis. The tibial (T) nerve has
beendissected from the common peroneal (P) nerve. Twowhite arrow-
headsmark the site of the end-end
anastomosis
of the peroneal nerve
performedpreviously during the first surgery. Focal bipolar stimulation
ofthe peroneal nerve isdepicted prior to an internal neurolysis.
normal fascicular structure was identified both proximally
and distally. The resultant gap was bridged by two sural
nerve grafts each measuring 8 em in length (Fig.120-5A).
.
ElectrophysiologicalMonitoring
The surgeon, with the aid of the electro diagnostician.
should work in the operating room to assess carefully both
the anatomical and functional integrity of motor and sen-
sory peripheral nerves.13During positioning of the patient,
electrodes are placed in relevant muscles as well as adja-
cent to relevant peripheral nerves, either on the skin sur-
face or percutaneously. In addition, electrodes are placed
over the spine and contralateral parietal scalp when central
propagation of sensory nerve impulses is to be monitored.
Use of regional or local anesthetic blocks or a tourniquet is
avoided so as not to compromise intraoperative electro-
physiological testing. In addition, no long-acting muscle
paralytics are given. Direct electrical stimulation of nerves
is performed using bipolar electrodes to reduce stimulus
current spread to generate a biphasic square-wave pulse
with a duration of 0.05 to 0.10 msec. In general. we start
with a stimulus intensity of 0.5 mAand increase the ampli-
tude up to 5 mA using a frequency of 1 per second. The
functional integrity of motor nerve fibers can be assessed
through either visual observation or EMGdocumentation of
muscle contraction. Both the velocity and the amplitude of
a nerve conduction response can be measured. The velocity
of the response is influenced by the degree of myelination
whereas the amplitude of the response is determined by
the number of conducting nerve fibers.
When evaluating a peripheral nerve lesion in continuity,
the presence or absence of a NAPacross the lesion deter-
mines the need for resection of a damaged nerve segment.14
Arecordable response across a traumatic lesion in continuity
indicates the presence of at least several thousand function-
ing nerve fibers.sSuch conducting lesions imply axonotmetic
lesions and therefore require no further surgicalrepair due to
the high probability of clinical recovery of function through
regeneration. In contrast, lesions in continuity without a
nerve conduction response should be surgicallyresected and
the nerve ends approximated usinggrafts when indicated.
. SurgicalTechniques
The surgical techniques applicable to peripheral
nerve
surgery include both external and internal neurolysis. Ex-
ternal neurolysis involves freeing nerves circumferentially
from the surrounding tissues and is almost always per-
formed to isolate nerves so that intraoperative stimulation
and recording can be done (Fig. 120-6). Internal neuroly-
sis is indicated for partial nerve lesions requiring a split re-
pair in which functioning nerve fascicles are separated
from nonfunctioning scarred intraneural tissue.1.1S-17This
procedure has the potential to injure regenerating axons
and should be performed with electrophysiological guid-
ance. The general technique of an internal neurolysis in-
volves first dissecting from a known, unscarred segment of

894
PeripheralNerve:Pathologyof the BrachialPlexus
the nerve to the more scarred region. Conducting fascicles
are spared and nonfunctioning
elements
are repaired
either end to end or with an interposition
nerve graft.
An end-to-end repair is preferred if the gap is small and
the two ends can be approximated without significant ten-
sion becausetension can impair recovery of nerve function. If
not, then the two ends should be approximated using inter-
position nerve grafts to avoid tension with the extremity in
full extension. Common donor nerves for grafting are har-
vested from autologous superficial sensory nerves such as
the sural nerve. Finemonofilament sutures (i.e.,7-0 to 10-0)
placed within the external or internal epineurium should be
used to approximate either single or groups of fascicles.The
nerve ends should be resected back to healthy fascicles and
every attempt should be made to maintain the original orien-
tation of the two nerve ends to optimize recovery of function.
However, anatomical fascicular continuity still does not guar-
antee axonal regeneration.
Two leading causes of regenera-
tive failure across the suture repair site are inadequate prepa-
ration of the nerve stumps and persistent tension. Both of
these factors can lead to the formation of intraneural scar,
which interferes with regenerating
nerve fibers.
.
Case History: PartV
Eight months following the second surgery, the patient be-
gan to show clinical and electrodiagnostic evidence of rein-
nervation of peroneal supplied muscles. MRNperformed at
References
1.
Kline D. Hudson
A. Lower extremity
nerve:
operative
care and tech-
nique.ln:
Nerve Injuries.
Philadelphia:
WB Saunders;
1995:117-146
2.
Mackinnon
S, Dellon A. Nerve repair
and nerve grafts.
In: Surgery
of
the Peripheral
Nerve. New York: Thieme;
1988:89-129
3.
McGillicuddy
j. Clinical decision
making
in brachial
plexus
injuries.
Neurosurg
Clin N Am 1991 ;2:137-150
4.
Seddon H. Three types of nerve injury. Brain 1943;66:237-288
5.
Kline D. Hudson A. Acute injuries
of peripheral
nerves. In: Youmans j.
ed. Neurological
Surgery. 3rd ed. Philadelphia:
WB Saunders;
1990
6.
Zager E. Morphology,
physiology.
and electrophysiology
of peripheral
nerve degeneration
and regeneration.
In: Benzel E. ed. Practical
Ap-
proaches
to Peripheral
Nerve Surgery. Park Ridge, IL: American
Asso-
ciation of Neurological
Surgeons;
1992:13-24
7.
Iyer V.Understanding
nerve conduction
and electromyographic
stud-
ies. Hand Clin 1993;9:273-287
8.
Friedman W. The electrophysiology
of peripheral
nerve injuries.
Neu-
rosurg Clin N Am 1991 ;2:43-56
9.
Kimura j. Electromyography.
In: Electrodiagnosis
in Diseases of Nerve
and Muscle. 2nd ed. Philadelphia:
FA Davis; 1989:209-302
10.
Filler A. Howe F. Hayes C, et al. Magnetic
resonance
neurography.
Lancet 1993;341 :659-661
8 months already showed partial resolution of the high-
intensity
signal on T2 and STIRsequences seen previously
in the peroneal nerve distal to its graft repair site(Fig.
120-5C). At 16 months, the patient showed continued clini-
calimprovementand MRN showed normalization of the1'2
signal in the peroneal nerve distal to the site of surgical
graft repair (Fig. 120-5D).
.
PostoperativeCare
Following a peripheral
nerve injury, it is extremely impor-
tant that patients undergo regular physical therapy,both
supervised and on their own, to maintain range of move-
ment and avoid immobilization as well as to optimizethe
recovery of motor function as reinnervation of musclesoc-
curs. Follow-up electrodiagnostic studies can be veryuseful
in detecting early signs of muscle reinnervation
several
months
prior to clinicallyevident muscle contraction.
. Summary
This review presents a set of general principles that canbe
applied clinically to evaluate and treat traumatic peripheral
nerve injuries. It is our premise that the diagnosis and treat-
ment of peripheral nerve injuries follows logicallyfroman
understanding of the basic biological responses of periph-
eral nerves following injury and during recovery.
11.
Dailey A, Tsuruda jS. Filler AG. et al. Magnetic
resonance
neurography
of peripheral nerve degeneration and regeneration. Lancet 1997;350:
1221-1222
12.
West A, Haynor D, Goodkin
R. et al. Magnetic
resonance
imaging sig.
nal changes in denervated muscles after peripheral nerve injury.Neu-
rosurgery
1994;35:1077-1086
13. Kliot M, Slimp j. Techniques and assessment
of peripheral nerve
function at surgery. In: Loftus C. Traynelis V. ed.lntraoperative
Moni-
toring
Techniques
in
Neurosurgery.
New
York:
McGraw-Hili:
1993:275-285
14.
Oberle j.Antoniadis
G, Rath SA. et al. Value of nerve action potentials
in the surgical management
of traumatic
nerve lesions. Neurosurgery
1997;41 :1337-1344
15. Sunderland S. Nerve Injuries and Their Repair. New York:Churchill
Livingstone;
1991
16. Wood MB. Compressive neuropathy of the lower extremity. In:Gel-
bermann
R, ed. Operative
Nerve Repair
and Reconstruction.
Vol2.
Philadelphia:
j.B. Lippincott;
1991 :1197-1209
17.
Lundborg G. Compression
and stretching.
In: Nerve Injury and Repair.
New York: Churchill Livingstone;
1988:1-37
"'---

121
CompressiveLesions of the Peripheral Nerve
LisaL.Guyot and Setti S. Rengachary
. Pathophysiology
. Entrapment of the Median Nerve bythe
Supracondylar Process of the Humerus
andStruthers' Ligament
Anatomy
ClinicalPresentation
Electrodiagnosis
. Entrapment of the Median Nerve at the Elbow
and Forearm (Pronator Syndrome)
Anatomy
ClinicalPresentation
Electrodiagnosis
. Anterior Interosseous Nerve Syndrome
(Kiloh-NevinSyndrome)
Anatomy
ClinicalPresentation
Electrodiagnosis
. MedianNerve Entrapment at the Wrist:
CarpalTunnel Syndrome
Anatomy
Etiology
ClinicalPresentation
Electrodiagnosis
. Entrapmentofthe RadialNerveabovethe Elbow
Anatomy
ClinicalPresentation
. Posterior Interosseous Nerve Entrapment
Anatomy
ClinicalPresentation
Electrodiagnosis
Entrapmentneuropathies are a group of disorders of the pe-
ripheralnerves that must be suspected in patients with loss
offunction.pain, or paresthesias in the anatomical distribu-
.
Cubital Tunnel Syndrome
Anatomy
ClinicalPresentation
Electrodiagnosis
.
UlnarNerveCompressionat the Wrist
(Guyon'sCanalSyndrome)
Anatomy
ClinicalPresentationand Electrodiagnosis
.
Suprascapular Entrapment Neuropathy
Anatomy
ClinicalPresentation
Electrodiagnosis
.
Thoracic Outlet Syndrome
Anatomy
ClinicalPresentation
Diagnosis/Electrodiagnosis
.
MeralgiaParesthetica:Syndromeofthe Lateral
FemoralCutaneousNerveofthe Thigh
Anatomy
ClinicalPresentation
Diagnosis
.
Saphenous Nerve Entrapment Syndrome
Anatomy
ClinicalPresentation/Diagnosis
.
TarsalTunnel Syndrome
Anatomy
ClinicalPresentation
Electrodiagnosis
tion of the nerve. Most commonly, the entrapment
of a
nerve in the extremities tends to occur at the site of a joint
where a fibro-osseous
tunnel is formed. If the tunnel
895

896
Peripheral Nerve: Pathology of the BrachialPlexus
becomes smaller because of an osteophyte. hypertrophy of
the synovium. abnormal tissue growth. or callus from a
fracture. the nerve becomes compressed.
In addition.
entrapment
can occur when
a fibrotendinous
arcade
compresses down on a traversing
nerve during active
muscle contraction.!
.
Pathophysiology
The pathophysiological changes following nerve compres-
sion are considered a continuum of changes depending
upon several factors-the degree. rate. and duration of com-
pression. Amild and brief compression causes a conduction
block in the nerve that can be transient and reversible. Ase-
vere. sustained compression can cause structural damage
and a permanent deficit.
Different properties of nerve fibers cause them to react
differently
to compression.
Nerves containing
more
epinerium and connective tissue than nerve fascicles are
less susceptible to compression. Nerve compression can
cause impairment of intraneural blood flow. especially the
venous return. which can cause intrafasicular ischemia.
edema. and a subsequent
increase in pressure on the
nerve.2 More centrally located nerve fibers are generally
spared at the expense of the superficial fibers due to the
distance from the compression. The compression can also
impede anterograde
and retrograde
axonal transport.
Blockage of the anterograde
fast and slow transport.
which carry membrane-associated
materials
and cy-
toskeletal proteins. can lead to swelling of the nerve ter-
minal proximal to the site of compression. Blockage of the
retrograde
flow denies
the nerve
cell body of neu-
ronotrophic factors and leads to wallerian degeneration.
The combined loss of anterograde and retrograde axonal
transport leads to impaired membrane permeability and
conduction block.
In cases of diabetes mellitus. in which peripheral neu-
ropathy occurs commonly. the accumulation of sorbitol. a
metabolite of glucose. causes endoneurial edema and in-
creased pressure on the nerve.3 This increase in pressure
can lead to microvascular ischemia and cause even further
damage to the nerve.
.
Entrapmentofthe MedianNerve
by
the
SupracondylarProcessof the Humerus
and Struthers' Ligament
Anatomy
The supracondylar process is a rare anomaly that occurs in
o 0.7 to 2.7%of the population and is seen more commonly
in Caucasians. It is a small bony process arising from the
medial surface of the humerus. 5 to 7 cm above the medial
epicondyle. In most cases.a fibrous ligament (Struthers' liga-
ment) extends from the supracondylar process to the medial
,>--
Mediann.
Brachiala.
Supracondylar
process
Ugament of
Struthers
Figure 121-1
Supracondylar process and the ligament ofStruthe~.
epicondyle. enclosing a fibro-osseous foramen through
which
the
median
nerve.
brachial
artery. and veinpass
(Fig. 121-1).
In cases in which the process is present.there
lies a potential to cause a high median nerve entrapment
neuropathy.
ClinicalPresentation
Patients
with
a supracondylar
process are generally
asymptomatic and the condition is incidentally foundona
physical exam or seen on a plain x-ray. The patientmay
feel a localized aching pain over the elbow or experience
weakness in the hand grip and pronation as wellastin.
gling in the lateral three digits. There may be objective
weaknessin the pronatorteres. flexorcarpiradialis,flexor
pollicuslongus. flexordigitorum sublimis.lateralhalfof
the flexor digitorum profundus. and thenar muscles.There
may be sensory loss in the median nerve distribution.
Pronator weaknessdistinguishes this syndromefromthe
pronator and anterior interosseous nerve syndromes.Pa.
tients may also experience symptoms resultingfrom
brachial artery ischemia. and if this is the case anarteri.
ogram should be performed.
Electrodiagnosis
Nerve conduction
studies may show slowing of the conduc-
tion velocity in the median nerve in the arm. Electromyog.
raphy may show denervation
potentials in the muscles
supplied by the median nerve.

121
Compressive lesions
897
. Entrapmentof the Median Nerve
atthe Elbowand Forearm
(PronatorSyndrome)
Anatomy
Themedian nerve arises from two roots from the medial
andlateral cords of the brachial
plexus
and then crosses
anteriorto the brachial
artery
in the midarm
(Fig. 121-2).
Atthe front of the elbow it lies behind the bicipital aponeu-
rosis(Iacertusfibrosis) and in front of the brachialis muscle.
The nervethen enters the forearm by passing between the
twoheads of the pronator
teres. It is at this point that the
anteriorinterosseous nerve is given off from the posterior
surfaceof the median nerve. The median nerve then passes
under the fibrotendinous arcade that represents the origin
ofthe flexor digitorum
sublimis
muscle.
The nerve
then
continuesdown the forearm superficial to the flexor digito-
rumprofundus
and deep to the undersurface
of the flexor
digitorumsublimis.
ClinicalPresentation
Themediannerveis susceptibleto compressionbyany of
thethree structures in the elbow and proximal forearm:
(1)the lacertus fibrosis, (2) the two heads of the pronator
teres,and (3) the sublimis bridge. It is clinically impossible
todistinguishbetween these different sites of compression,
Mediann.
Pronator teres
Brachiala.
Bicipital
aponeurosis
Pronator teres
Figure121-2
Anatomy ofthe median nerve in the cubital fossa.
and exploration of the nerve in this area should include ex-
amination of all three locations.
Patients generally complain of aching pain in the forearm
or weakness of the forearm muscles or weakness of the hand
grip with tingling in the index finger or thumb. There are
generally no nocturnal symptoms, as in carpal tunnel syn-
drome (CfS). Patients recently starting a new job or hobby
requiring repetitive pronation and supination should raise
suspicion of entrapment at these sites. There may be tender-
ness on palpation and induration of the pronator teres mus-
cle. There may be mild to moderate weakness of median
nerve-innervated
muscles, especially the flexor pollicus
longus and the abductor pollicus brevis. In cases of severe
compression, flexionofthe first three digits may be impaired
leading to the "benediction attitude" formation of the hand.
Electrodiagnosis
Nerve conduction velocity may be slowed in the forearm
segment of the median nerve, but the distal sensory and
motor latencies are normal unless there is an overlying CfS.
Electromyography may show denervation potentials in the
median musculature distal to the compression.
.
Anterior InterosseousNerve Syndrome
(Kiloh-Nevin Syndrome)
Anatomy
The anterior interosseous nerve, which is primarily a motor
nerve, arises from the median nerve as it passes between
the heads of the pronator teres. It then descends in front of
the interosseous membrane between the flexor digitorum
profundus and the flexor pollicus longus, supplying these
two muscles. It then terminates in the pronator quadratus
near the wrist joint.
ClinicalPresentation
This syndrome primarily occurs after forearm fractures.4
Symptoms of anterior interosseous nerve syndrome (AINS)
include an aching pain in the elbow and forearm. The prin-
ciple difficulty in this syndrome is in moving the index and
middle fingers. Physical exam reveals weakness in the long
flexors of the thumb (flexor pollicus longus) and index
finger. This can be demonstrated
by an abnormal pinch
posture of the hand. Thisis caused by extension or hyperex-
tension of the thumb and index finger with a flexion of the
metacarpophalangeal
joint of the thumb and interpha-
langealjoint of the index finger.
The pronator quadratus muscle is difficult to test clini-
cally because of the simultaneous contraction of the more
powerful pronator teres. But, when the elbow is examined
in flexion, the pronator teres is at a mechanical disadvan-
tage, and any weakness of the pronator quadratus may
become apparent. There is no sensory deficit.

898
PeripheralNerve:Pathologyof the BrachialPlexus
Electrodiagnosis
Electromyography may show evidence of abnormal mem-
brane irritability with loss of motor units in any or all of the
muscles supplied by the anterior interosseous nerve.
. Median Nerve Entrapment at the Wrist:
CarpalTunnel Syndrome
Anatomy
as
results from compression of the distal median nerve
within the carpal tunnel. The carpal tunnel is a fibro-
osseous tunnel in the wrist that is bounded dorsally by
the carpal bones and ventrally by the transverse carpal
ligament (a tough, fibrous flexor retinaculum) (Fig. 121-3).
The carpal bones form a shallow trough that is converted
into a tunnel by the carpal ligament. This tunnel contains
the median nerve and the tendons of the flexor digitorum
sublimis, flexor digitorum profundus, and flexor pollicus
longus.
Etiology
There are many causes of CTS,and in the majority of cases
no definite etiology can be found. The most common cause
is repetitive motions of the wrist as with patients who
frequently type, knit, drive, or paint. Some patients are pre-
disposed to this condition because of a congenitally small
carpal tunnel canal. In addition, numerous clinical condi-
tions are associated with as
and are listed in Table121-1.
More common etiologies include pregnancy, maintenance
dialysis,and burns involvingthe wrist.
Clinical Presentation
Women are more commonly affected than men in a ratio of
7:3. Most patients are between the ages of 40 and 60 at the
onset of symptoms. Symptoms include burning, aching, or
Mediann.
Ulnar artery
and nerve
Carpal
bones
Figure 121-3
Anatomy
of the carpal tunnel at the wrist.
tingling in the distribution
of the median nerve,which
includes the radial half of the hand and the lateralthree
digits. Some patients experience symptoms in the entire
hand or even the forearm or shoulder. Often the symptoms
occur at night, and, upon awakening, the patientsfre-
quently shake the hand or massage the wrist to relieve
their symptoms.
Strenuous
use of the hand commonlyex-
acerbates the symptoms, which are usually more promi.
nent in the dominant hand. However, symptoms maynot
developuntil the patient has restedseveralhoursafterac-
tivity. Weakness of the grip is often a late finding,butafew
patients may present with atrophy and weakness andfew
complaints
of pain.5
In the early stages of the syndrome, there are few objective
findings. Two mechanical tests may be useful.ATinel'sign
may be elicited by tapping on the median nerve at thewrist
A positive sign causes tingling or a shocklike sensation overthe
distribution of the nerve. APhalen's test is positive if flexingthe
wrist to 90 degrees for 1 minute results in tingling overthedis-
tribution of the nerve. These tests have a high incidenceof
false-positivesand must be used as onlya part ofthediagnosis.
A loss of light touch or pinprick over the mediannerve
distribution may be observed. Weakness of the opponens
pollicis muscle may be present. Advanced cases mayshow
signs of atrophy of the thenar eminence, especiallyinthe
abductor pollicis brevis.
Electrodiagnosis
The most important and sensitive test for as
isprolonged
sensory latency. The sensory evoked response willshowa
reduction in amplitude and may even be absent. Motor
latency abnormalities occur late in the course of thedis-
ease. Needle electro myographic test may show lossof
motor unit potential
and the presence
of denervation po.
tentials in the thenar muscles. It is important to testthe
ulnar nerve in the hand to rule out the possibilityof
peripheral neuropathy.
.
Entrapment of the Radial Nerve
above the Elbow
Anatomy
The radial nerve originates from the posterior cordofthe
brachial plexus. It primarily supplies the extensorsofthearrn
and forearm.Aftergivingoffa branch to the tricepsthenerve
curves around the humerus. Just prior to entering thefore-
arm, the nerve gives off branches to the brachioradialisand
extensor carpi radialis.In the proximal forearm it dividesinto
two branches: the sensory nerve, which innervatestheskin
over the dorsum and radial side of the hand, thumb, andin.
dex and middle fingers, and the posterior interosseous nerve
(PIN).Entrapmentofthe sensorybranchofthe radialnerve
leads to a sensory deficit in the previously mentioned
anatomical distribution. The PINenters the supinatormuscle
where it is bound (30%) by the arcade of Frohse (Fig.121-4~
It then continues into the forearm and gives offbranchesto
the extensor muscles of the wrist and fingers.
l

121
CompressiveLesions
899
Table121-1
RiskFactorsinthe Pathogenesis of CarpalTunnelSyndrome
Local Factors
REDUCTION
IN THE CAPACITY
OF THE CARPAL
CANAL
Idiopathic or familial thickening of the transverse carpal ligament
Congenitally small carpal canal
Malunion or callus following Colles' fracture or fracture of the carpal bones
Improper immobilization of the wrist ("cotton loader position")
Unrestricted dislocations of the wrist or intercarpal joints
Compression by cast
INCREASED
VOlUME
OF THE CONTENTS
OF THE CARPAL
CANAL
Anomalous muscles and tendons
Hypertrophic tenosynovitis
Persistent median artery with or without thrombosis, aneurysm, arteriovenous malformation
Acute palmar space infections
Masses: neurofibroma. hemangioma,
lipoma. ganglion cyst. gouty tophus, xanthoma
Systemic
Factors
INFLAMMATORY
AND AUTOIMMUNE
DISORDERS
Rheumatoid arthritis
Dermatomyositis
Scleroderma
Polymyalgia rheumatica
Increased Susceptibility of Nerves to Pressure
Amyloidosis
Hereditary neuropathy with liability to pressure palsies
Alcoholic or diabetic polyneuropathy
Proximiallesions of the median nerve ("double crush" syndrome)
Other poyneuropathies
Metabolic Disorders
Mucopolysaccharidoses
Mucolipidoses
Amyloidosis
Gout
Factors Unique to Women
Pregnancy and lactation
Contraceptive
pills
Menstrual cycles
Menopause
Toxicshock syndrome
Eclampsia
Other Hormonal Factors
Myxedema
Acromegaly
Other Systemic Factors
Obesity
Raynaud'sdisease

900
Peripheral Nerve: Pathology of the BrachialPlexus
ClinicalPresentation
Entrapment of the radial nerve above the elbow occurs
most commonly in patients who are using crutches. Also
known as the Saturday Night palsy, this can occur with dis-
placed fractures of the humeral shaft. In these cases, there
will be paralysis of the (brachialis), wrist extension, digital
extension, and sensory deficits over the dorsum of the ra-
dial aspect of the hand.
.
PosteriorInterosseousNerve
Entrapment
Anatomy
The PINsupplies the extensor carpi radialis brevis and the
supinator muscle before entering the arcade of Frohse.This
arcade is a tough fibrotendinous structure at the origin of
the supinator muscle and is the most common site of en-
trapment for the nerve. Fullpronation of the forearm causes
pressure on the nerve by the sharp tendinous edge of the
origin of the extensor carpi radialis brevis muscle.
The PIN, which has no cutaneous sensory component,
traverses the supinator muscle then winds around the lat-
eral side of the radius to emerge on the dorsal aspect of the
forearm in the interval between the superficial and deep
Radialn.
Posterior
interosseous
n.
Arcadeof
Frohse
Figure 121-4
Anatomicaldiagramofthe arcade of Frohse.
extensor muscles. It then gives off many muscular branches.
which supply the extensor
digiti minimi, extensor digito-
rum, extensor carpi ulnaris, abductor pollicislongus,exten.
sor pollicis longus, and brevis and extensor indicis.
ClinicalPresentation
Patients
present
with paralysis
in the distribution ofthe
nerve;
however, there is no wrist drop. This is becausethe
extensor carpi radialis longus is supplied by the radialnerve
proximal
to its terminal
branching.
When the patient at.
tempts
to extend
the wrist, it deviates
radially due tothe
weakness of the extensor carpi ulnaris. The cardinalfinding
is "finger drop" -the
inability to extend the metacarpopha.
langeal joints of the fingers and thumb. Extension ofthefin.
gers at the interphalangeal
joints
of the fingers is possible
because this is an ulnar and median nerve mediated action.
Extension
of the thumb
at the interphalangeal
joint isnot
possible
because
of the weakness
of the extensor pollicus
longus. There is no sensory loss.
Electrodiagnosis
Needle electromyography may show denervation ofthe
nerves innervated by the PIN.Absence ofthese findingsin
the brachioradialis,extensorcarpiradialislongus,extensor
carpiradialisbrevis,and supinatorhelpslocalizethelesion
to the area of the arcade of Frohse. Nerve conductionstud.
iesmayshowslowinginthe caseofentrapment.
. Ci,ibital
Tunnel
Syndrome
Anatomy
The cubital
tunnel
syndrome
(CuTS), or tardy ulnar
palsy/Feindel-Osborne
syndrome,
results
from entrapmem
of the ulnar nerve at the elbow. The cubital tunnel (CuT)is
located
medial
to the elbow joint
and is a fibro-osseous
tunnel
that is roofed by the aponeurotic
attachment ofthe
two heads
of the flexor carpi ulnaris
and a tough fascial
band that bridges these two heads (Fig. 121-5). The flooro[
the CuTis the medial collateral ligament of the elbow.This
fascial band spans, in an arcade-like manner, the medial
epicondyle,
and the olecranon
process. The aponeurosisis
referred to as the arcuate ligament,
Osborne's band. cubital
tunnel
retinaculum,
or triangular
ligament.
During flexion.
the volume of the tunnel decreases,
causing entrapmento[
the nerve. This occurs because the attachments of the flexor
carpi
ulnaris
(the
medial
epicondyle
and the olecranon
process)
are farthest
apart
during
flexion. This increased
distance stretches
the fascial band between
the two anden-
croaches on the cubital tunnel. This is aggravated if flexion
of the elbow is coupled with contraction of the flexorcarpi
ulnaris to initiate wrist movement, as during hammeringor
shoveling.
The ulnar nerve arises from the most distal branch ofthe
medial cord of the brachial plexus. It has no branches inthe
arm. Prior to entering
the cubital tunnel
it does giveoffar.
ticular
branches
to the elbow joint.
The branches tothe

121
Compressivelesions
901
Humerus
Ulnarn.
Medial
epicondyle
Radius
Fascialroof
ofcubital
tunnel
Ulna
Olecranon
Aexor carpi
ulnaris
Rgure121-5
Anatomy of the cubital tunnel.
flexorcarpi ulnaris and the medial half of the flexor digito-
rumprofundus are given off distally to the cubital tunnel;
yet,because the fasicles that innervate these two muscles
aresituated deeply in the nerve, they are generally not in-
volvedin the entrapment syndrome.
ClinicalPresentation
Themajor presentingsymptomsof CuTSincludeweakness
andatrophy of the intrinsic hand muscles and tingling and
numbnessof the medial two fingers. Patients may complain
ofhaving a clumsy hand and dropping things. Men are af-
fectedthree times more commonly than women and the
syndromeis most common between the agesof 30 and 60.
Inthe majority
of cases no etiologic factor is identified.
However,the entrapment
syndrome can be caused by
trauma(heterotopic bone formation), encroachment on the
nerveby soft tissue (rheumatoid
arthritis),
or congenital
anomalies.There are two congenital anomalies that may af-
fectthe nerve: the presence of the epitrochleoanconeus
muscleor a partial (10%) or complete (2%) subluxation of
thenerve at the elbow. The subluxation occurs secondary to
laxityof the arcuate ligament, variations in the depth of the
ulnargroove, or hypertrophy of the medial triceps muscle.6
Paresthesiasalong the inner border of the hand or the
fourthor fifth digits are the most common symptom. Sen-
sorylossto light touch and pinprick may be detected along
themedial one and one half fingers and the hand. Because
theulnar nerve contains a greater number of motor than
sensoryfibers at the elbow, motor findings are a more sig-
nificant part of the clinical
picture. On objective testing
thereis weakness of the ulnar innervated musculature of
the hand including
the palmaris
brevis, abductor digiti
quinti,opponens digiti quinti, flexor digiti quinti, adductor
pollicus,medial two lumbricals, and all of the interossei. An
earlysign of ulnar nerve entrapment
is weakness of the
third palmar interosseous muscle, which
results in an
abductedsmall finger (Wartenberg's sign). There may be a
positive Tinel's sign elicited at the elbow. Froment's sign
may be elicited by asking the patient to grasp a piece of
cardboard between the index finger and the thumb against
resistance. In patients
with
weakness of the adductor
pollicus, there will be flexion of the first interphalangeal
joint and the thumb. Weakness in the flexor carpi ulnaris
and medial half of the flexor digitorum profundus is present
infrequently for reasonsalready stated.
Electrodiagnosis
The characteristic
electrodiagnostic
finding
is a delay in
the conduction of the ulnar nerve across the elbow. It is
important
to flex the elbow during the examination
in or-
der that the nerve is maximally stretched. The sensory la-
tency is prolonged and the amplitude
of the motor re-
sponse in the abductor digiti quinti
is reduced. A needle
examination
of the ulnar-innervated
muscles may show
denervation potentials. The CuTSshould be differentiated
from lesions affecting the spinal cord or nerve roots at C8
and n,
including
spinal cord tumors, syringomyelia,
or
cervical disk disease. These lesions can also present with
Horner's syndrome, which can help in the differential
di-
agnosis. In addition, lesions affecting the brachial plexus at
the lower trunk or medial cord should also be ruled out
such as Pancoast tumor, entrapment of the ulnar nerve at
the wrist (Guyon's canal), or polyneuropathy
(due to dia-
betes or alcoholism)
. Ulnar Nerve Compression at the Wrist
(Guyon's Canal Syndrome)
Anatomy
The ulnar nerve descendsin the distal forearm and lies
lateral to the flexor carpiulnaristendonand medial to the
ulnar artery. Approximately 5 to 8 cm above the wrist
crease, it gives off the cutaneous branch to the hand. At
the wrist it enters Guyon's canal, which is an oblique fi-
bro-osseous tunnel that lies within the proximal part of
the hypothenar eminence. The roof of the tunnel is
formed by the volar carpal ligament and the floor is
formed by the transverse carpal ligament. The pisiform
bounds the canal proximally and medially and the hook of
the hamate bounds the canal distally and laterally. There
is no lateral wall proximally due to the fusion of the pal-
mar fascia with the transverse carpal ligament. The ulnar
nerve and artery pass through the tunnel and in the mid-
dle of the canal the nerve divides into superficial and
deep branches. The superficial branch proceeds in line
with the main nerve and, upon exiting the canal, supplies
a branch to the palmaris brevis muscle
and sensory
branches to the little fingerand ulnar half of the ring fin-
ger. The deep motor branch, along with the ulnar artery,
turns around the hook of the hamate. At this turn, it
passes under a tough fibrotendinous arch (pisohamate
hiatus), which gives rise to the hypothenar musculature.
This is the most vulnerable site of compression of the
deepmotorbranchofthe ulnar nerve.

902
PeripheralNerve:Pathologyof the BrachialPlexus
TypeI
Figure121-6
The three types of ulnar nerve compression
near the wrist.
Type I!
Type III
Clinical Presentation and Electrodiagnosis
There are various etiologies of this entrapment syndrome,
the most common being occupational trauma and external
compression from a ganglion cyst. Also,anomalous muscles
can encroach on the canal; the most common (61%)being
the accessory digiti minimi muscle, which has its origin
from the anterolateral fascia and traverses the canaJ.7En-
trapment of the ulnar nerve at the wrist must be suspected
if the nerve is nontender at the elbow, elbow flexion does
not reproduce the symptoms, and dorsal ulnar sensation in
the hand is intact. This is due to sparing of the dorsal ulnar
branch, which divides from the main trunk of the nerve
9 cm proximal to the pisiform (Cases from hand surg).
There are three
types of syndromes
that
have been
described depending on the location of the entrapment4
(Fig.121-6).
In the type I syndrome, the nerve is compromised just
proximal to or in Guyon's canal. Sensory loss is in an ulnar
distribution and there is weakness of all ulnar innervated
muscles in the hand. Electrodiagnostic results include nor-
mal conduction velocity of the ulnar nerve across the elbow,
prolonged distal latency to the abductor digiti minimi and
first dorsal interossei, and prolonged sensory latency and
diminished evoked sensory responses.
The type 1\ syndrome, which is the most common,
spares sensation of the hand but causes weakness in the
muscles of the hand innervated by the deep branch of the
ulnar nerve. The nerve in the syndrome is compressed at
the pisohamate hiatus. The branch to the abductor digiti
quinti and other hypothenar muscles is frequently spared
because it arises just proximal to the pisohamate hiatus.
To distinguish
between
ulnar
nerve
compression
atthe
cubital
tunnel
and the wrist
it is helpful
to elicit a "pal-
maris brevis sign." Normally, when the patient abducts
the little finger, there
is simultaneous
contraction ofthe
palmaris
brevis. If this is absent,
the entrapment
oftheul-
nar nerve is at the cubital tunnel. This response isusually
preserved if the compression of the ulnar nerve isatthe
wrist. Electrodiagnostic
tests may reveal normal motor
conduction velocities across the elbow and wrist, normal
sensory latencies and evoked responses,
normal distal
motor latency to the abductor
digiti quinti with prolonged
latency
to the first dorsal
interossei,
or denervation
potentials
in the first dorsal interossei
but not in the
abductor
digiti quinti.
The type 11\syndrome is characterized by sensoryloss
alone due to compression
at the distal portion of Guyon's
canal. It is caused by pathology affecting the superficial
branch at the most distal part of the canal. This syndromeis
rarely seen.
.
Suprascapular Entrapment Neuropathy
Anatomy
The suprascapular nerve arises as a large branch from the
superior trunk (C5-C6) of the brachial plexus. Its motor
component
supplies
the supra-
and infraspinatus
muscles
and its only sensory component supplies the posterior
L

121
CompressiveLesions
903
capsuleof the shoulder joint. The nerve travels through the
posteriortriangle of the neck and parallel to the body of
theomohyoid muscle (Fig. 121-7). It then courses under
thetrapezius, through the suprascapular notch below the
suprascapular ligament to the supraspinous
fossa. The
suprascapular artery
passes
over
the
suprascapular
ligamentto join the nerve in the supraspinous fossa. After
supplyingthe supraspinatus, the nerve travels around the
lateralborder of the spine of the scapula to the infraspinous
fossawhere it supplies the infraspinatus muscle.
Entrapment may occur at two places: the lateral edge of
thescapula in the spinoglenoid notch from a hypertrophied
inferior transverse
scapular
ligament causing selective
infraspinatusdenervation or the more common site of en-
trapment,which is within the suprascapular notch under
thesuprascapular ligament.
ClinicalPresentation
Shoulderpain is the most common presenting symptom in
suprascapular entrapment neuropathy (SEN).The onset of
the pain may be insidious or acute due to trauma. This
painis deep and is most likely due to compression of the
articular branches supplying the capsule of the shoulder
joint.The pain is referred to the posterior aspect of the
shoulder joint
and adjacent
scapula. Weakness of the
supra-and infraspinatus muscles is common as well as at-
rophyofthese muscles.Theatrophy may be pronounced
Dorsalscapular
n.(C5)
lavatorscapulae
(C5,6)
Suprascapular m.
I
Suprascapular n.
Rhomboideous
minorm.
Infraspinatus m.
Rhomboideous
majorm.
Lowersubscapular
n.(C5, 6)
Figure121-7
Anatomy of the suprascapular
nerve.
and mere inspection of this region can make the diagnosis.
The atrophy of the infraspinatus, which is a more superfi-
cial muscle, is more readily apparent than atrophy of the
supraspinatus,
which lies deep to the trapezius muscle.
Supraspinatus weakness is manifested by a decrease in the
first 15 degrees of abduction of the arm. Infraspinatus
weakness results in decreased external rotation of the arm
with the elbow in 90 degrees of flexion. There is no sen-
sory loss seen in this syndrome. Often, one must attempt
to differentiate between a suprascapular entrapment neu-
ropathy and a rotator cuff tear. Both cases may have atro-
phy of the supra- and infraspinatus muscle atrophy and
difficulty abducting the shoulder in the presence of a nor-
mal deltoid muscle. Electrodiagnostic tests are helpful be-
cause in the case of rotor cuff tears there are no denerva-
tion potentials; the atrophy is due to disuse. Arthrography
demonstrates
the communication
between the gleno-
humeral joint and the subacromial bursa through the tear
in the cuff.
Electrodiagnosis
The presence of denervation potentials confined to the
supra-
and infraspinatus
muscles is the most helpful
diagnostic test. Because the suprascapular nerve runs deep,
measurement
of its conduction
velocity
is difficult.
However, delayed conduction
from Erb's point to the
supraspinatus, can indicate nerve entrapment.
Deltoidm.
Teres minor m.
Axillaryn.
(C5,6)
Superior
lateralbrachial
cutaneous n.
Radialn.
(C5, 6, 7, 8, T1)

904
PeripheralNerve: Pathologyof the BrachialPlexus
. Thoracic Outlet Syndrome
Anatomy
The thoracic outlet is bordered by the vertebral column
posteriorly, the sternum and clavicleanteriorly and the first
rib laterally. The anterior and middle scalene muscles arise
from the cervical vertebral column and insert on the first
rib. The resultant triangle contains the subclavian artery
and the brachial plexus. The subclavianvein crosses the first
rib ventral to the anterior scalene muscle. The rib, artery,
vein, and brachial plexus pass between the clavicle and the
first rib then continue behind the pectoralis minor muscle
into the arm.
Entrapment of this neurovascular bundle may occur at
three different sites: between the anterior and middle sca-
lene muscles and the first rib, between the first rib and the
clavicle,and beneath the pectoralis minor muscle.
Clinical Presentation
The thoracic outlet syndromes (TOSs)are a heterogeneous
group of disorders. The etiology of patients'
symptoms
must be differentiated according to the arterial, venous, or
neurological structure in the thoracic outlet that is being
compressed. The neurological thoracic outlet syndrome is
found primarily in young to middle-aged females. They
have clinical features related to the compression of the
(8- T1 nerve roots or proximal lower trunk of the brachial
plexus by a constricting band extending from the first rib
to a rudimentary "cervical rib" or a prominent (7 trans-
verse process.Theycomplain of pain in the medial forearm
and can exhibit decreased sensation along the medial fore-
arm or the fourth and fifth digits. They may also have
wasting of the lateral thenar muscles, especially the ab-
ductor pollicus brevis.s The atrophy may be limited to the
thenar eminence or include the intrinsic muscles of the
hand, the hypothenar eminence, or the medial forearm
muscles. There are no symptoms of arterial or venous in-
sufficiency seen.
Diagnosis/Electrodiagnosis
The diagnosis of this type of thoracic outlet syndrome can
be made based on clinical signs and symptoms as well as
plain x-ray of the neck, which may reveal a cervical rib or a
prominent C7 transverse process. Three-dimensional
CT
scans have been used with some success in delineating the
anatomy of the thoracic outlet in patients with suspected
TOS.9Electromyography (EMG)may show chronic axonal
loss in the lower trunk of the brachial plexus, and nerve
conduction studies show low amplitude median and ulnar
motor responses and lowulnar sensory responses with nor-
mal median sensory responses.
The signs and symptoms ofrOS, including the wasting of
the muscles in the hand along with the sensory changes in
the arm and hand, may be confused with entrapment neu-
ropathies of the elbow and hand. It is important, using
x-ray, EMG,and nerve conduction studies, to differentiate
these syndromes.
.
Meralgia Paresthetica: Syndrome
of the Lateral Femoral Cutaneous
Nerve of the Thigh
Anatomy
Meralgia paresthetica is a clinical syndrome causedbyen-
trapment
of the lateral
femoral
cutaneous
nerve. It isa
purely sensory nerve that arises from the second andthird
lumbar nerves ofthe
lumbar plexus. The nerve emergesat
the lateral margin of the psoas major muscle at the levelof
the crest of the ilium and descends
obliquely and forward
under the iliac fossa (Fig. 121-8). It then passes throughthe
inguinal ligament
near the anterior
superior iliac spine.The
nerve then proceeds under the fascia lata of the thighfor-5
em, and then becomes subcutaneous by piercing thefascia
lata. The nerve supplies the skin of the anterior lateralthigh
and gluteal region. The nerve can be entrapped at anyof
these
sites where
it traverses
through
or near one ofthe
above fascial bands, but the most common
site of entrap-
ment is at the inguinal canal. Anyfactor that causestraction
or pressure on the inguinal ligament, such as an obeseand
pendulous
abdominal
wall or an occupation
that requires
prolonged standing, tends to aggravate the symptoms.
Clinical Presentation
Obese, middle-aged males are the most common to present
with meralgia paresthetica.ln
20% of cases, the syndromeis
bilateral. It may also present during pregnancy with thein-
Figure 121-8
Anatomyofthe lateralfemoralcutaneous nerve.

..
121 Compressive
lesions
905
creased
tensioninthe anteriorabdominalwall.Inaddition,
bindingbelts or clothes or local irritations can cause the
syndrome.Local irritation includes direct trauma to the
nervesuchas a hematoma after iliac crest bone graft har-
vesting.Patients with this syndrome often complain of a
tingling,pricking, or crawling sensation in the distribution
ofthenerve-rarely do they describe pain. Sensory com-
plaintstend to be localized to the area innervated by the
anteriorbranch of the nerve. This may be because the ante-
riornervefibersare located directlybeneath the inguinal
ligamentand are more susceptible to compression. Sensory
lossmaybe present depending on the degree of compres-
siononthe nerve. There are no motor or reflex changes in
thisyndromeand, if present, should redirect the diagnosis.
Differentialdiagnosis in this syndrome should include up-
perlumbarintraspinal pathology or pelvicdisorders.
Diagnosis
Electrodiagnostictests are not usually helpful in making a
diagnosis.Thediagnosiscanbe madebasedon clinicalhis-
toryandthe sensorysymptomsinthe regionofthe nerve.
Asimplediagnostic test consists of administering a local
anesthetic(5 mLof 1%lidocaine) just medial to the ante-
riorsuperioriliac spine and waiting to see relief of the
symptoms.Ifthe sensory loss is more extensive or there is
muscleinvolvement,
appropriate
studies such as EMG, MRI
ofthelumbar spine, and computed tomography (Cf) of the
abdomenshould be performed to rule out another lesion.
. Saphenous Nerve Entrapment
Syndrome
Anatomy
Thesaphenous nerve arises from the femoral nerve in the
femoraltriangle and descends in the leg with the greater
saphenousvein to supply the skin on the medial aspect of
theleg and foot. After arising just below the inguinal
ligament,it enters the adductor canal (subsartorial canal,
Hunter'scanal), crosses the femoral artery from lateral to
medial,and then leaves the canal by piercing the subsartor-
ialfasciaalong with the descending genicular artery. It is a
purelysensorycutaneous nerve.Thearea where the nerve
traversesthe subsartorial fascia is the most common site of
entrapment.
ClinicalPresentation/Diagnosis
Thisyndrome is more common in young or middle-aged
individualsand in women more often than men. The
symptomsare typically aggravated by activity such as
climbingstairs and relieved with rest. Patients often com-
plainof pain along the medial aspect of the knee and
commonlythey have had an extensive workup with x-
raysandarthroscopyto rule out anyjoint problems.Often
thereis point tenderness
-10 to 12 em above the medial
aspectofthe knee where the saphenous nerve penetrates
the subsartorial fascia. Relief of the symptoms with a local
nerve block highly suggest
the diagnosis.
Again, any
motor or reflex changes should redirect the diagnosis.
Electrodiagnositic studies are usually not helpful in the
diagnosis.
.
TarsalTunnelSyndrome
Anatomy
Encroachment
on the tarsal tunnel causes compression
of the posterior tibial nerve, which is a terminal branch
of the sciatic nerve. The tarsal tunnel is posterior and in-
ferior to the medial malleolus. The roof of the tunnel is
formed by the flexor retinaculum
(lancinate
ligament),
which is a continuation of the deep fascia spanning this
area (Fig. 121-9). The bony floor is formed by the medial
aspect of the calcaneus and the posterior aspect of the
medial malleolus.
Numerous fibrous septa divide the
tunnel into rigid fibro-osseous compartments
that con-
tain tendons
and synovial sheaths and neurovascular
structures. The contents of the tunnel include (from an-
terior to posterior), the tendon of the tibialis posterior,
the tendon of the flexor digitorum longus, the posterior
tibial vessels, the tibial nerve, and the tendon
of the
flexor hallicus longus.
The posterior tibial nerve descends in the posterior as-
pect of the leg deep to the soleus muscle and enters the
tarsal tunnel behind the posterior tibial vessels. At this
point, or just distal, it divides into three branches:
the
calcaneal, medial plantar, and lateral plantar nerves. The
calcaneal branches have a variable origin and are purely
sensory branches. The medial and lateral plantar nerves
pass through individual fibrous septa in the origin of the
abductor
hallucis muscle. This is a point
of possible
entrapment.
These two branches
supply the intrinsic
muscles of the foot and provide sensory innervation
to
the sole of the foot.
Clinical Presentation
Approximately 50%of the patients who present with tarsal
tunnel syndrome have a history of trauma involving the
ankle. Tenosynovitis or venous
stasis
from prolonged
standing are other common causes. Men and women are
affected equally. Patients commonly present with symp-
toms of burning pain and paresthesias
in the plantar as-
pect of the foot.The pain may radiate up the medial aspect
of the calf.The heel is usually spared because the calcaneal
branches are variable in origin and may be given off prior
to the entrance of the nerve into the tunnel. Activity or
prolonged standing typically exacerbate
the symptoms
whereas rest relieves them. As is the case in CTS, the
symptoms are occasionally worse at night. There may be
weakness of the intrinsic muscles of the foot and a sensory
loss consistent with the distribution of the nerve. ATinel's
sign or point tenderness
may be elicited over the tarsal
tunnel.

906
PeripheralNerve:Pathologyof the BrachialPlexus
Posterior
tibial n.
Posterior
tibial a.
Flexor
retinaculum
Flexor
digitorum
tendon
Tibialis
posterior
tendon
Medialand
lateral
plantarnn.
Figure 121-9
Anatomyofthe tarsal tunnel.
Electrodiagnosis
Electrodiagnostic studies may reveal the following: (1)
normal conduction velocity of the posterior tibial nerve in
the leg, (2) prolonged distal motor latency to the abductor
hallicus (this represents the medial plantar branch) and
References
t.
Novak CB.Mackinnon
SE. Nerve injury in repetitive
motion
disorders.
Clin Orthop 1998;351 :10-20
2.
Friedman WA.The electrophysiology of peripheral nerve injuries. In:
Burchiel
Kj. ed. Neurosurgery
Clinics of North America.
Vol 2. no. 1.
Philadelphia:
WB Saunders;
1991 :43-56
3.
Dahlin LB.Archer DR. Mclean
WG. Treatment
with an aldose
reduc-
tase inhibitor can reduce the susceptibility of fast axonal transport
following nerve compression
in the streptozotocin-diabetic
rat.
Diabetologia1987;30:414-418
4. Tindell sc. Chronicinjuries of peripheral
nerves by entrapment.
In: Youmans JR. ed. Neurological Surgery. 3rd ed.
Philadelphia:
WB Saunders;
1990:2511-2542
Calcaneal
\ branches
abductor digiti quinti
(this represents
the lateral plantar
branch),
(3) decreased
amplitude
of evoked muscle
potentials
in the abductor hallicus and abductor digiti
quinti, and (4) absence of orthodromically inducedsensory
nerve
potentials
or decreased
sensory
nerve conduction
velocity.
5.
Szabo RM. Carpal tunnel
as a repetitive
motion
disorder.
(Iin Orthop
1998;351
:78-89
6.
Childress
HM. Recurrent
ulnar
nerve
dislocation
at the elbow.Clin
Orthop
1975;
108: 168-173
7.
Jeffery
AK. Compression
of the palmar
branch
of the ulnar nerveby
an anomalous
muscle.j
Bone joint
Surg
Br 1971 ;53:718-723
8.
Hardy
RW. Wilbourn
Aj. Thoracic
outlet
syndromes.
In: WilkinsRH.
Rengachary
SS. eds.
Neurosurgery.
2nd
ed.
New
York:
McGraw-Hili:
1996:3069-3072
9.
Remy j. Remy-jardin M.Artaud
D. et
al.
Multiplaner
and three.
dimensional
reconstruction
techniques
in CT: impact
on chestdis.
eases.
Eur RadioI1998;8:335-351

122
SupraclavicularApproach to
BrachialPlexus Surgery
DanielH. Kim, Steven D. Chang, and David G. Kline
. Indications
. Contraindications
. Advantages
. Disadvantages
. Anatomy
. Objective
. Surgical Technique
Themost common cause of injury to the supraclavicular
brachialplexus is trauma
sustained
from high-speed
motorcycleor automobile accidents, sports injuries, or
work-relatedaccidents, which usually result in stretch in-
juries.1-4Otherknowncausesof brachialplexusinjuryre-
quiringthe need for surgical intervention are listed later.
. Indications
. Tractioninjury
. Lacerationinjury (sharp knife or glass, blunt transection
frompropeller or chain saw)
. Penetrating injury from gunshot wound (GSW)or metal
fragments)
. Iatrogenicinjury
. Injectioninjury (regional anesthesia)
. Compressioninjury (thoracic outlet syndrome)
. Obstetricinjury (birth palsy)
. Nervesheath tumor, metastatic tumor
. Radiationinjury
. Contra indications
. Brachial plexitis
. Transientradiationplexopathy
. Multiplepseudomeningoceleon myelogram
Anesthesia and Positioning
Incision
Dissection
Donor Nerve Graft Harvesting
.
Surgical Repair
Laceration
Penetrating/GSW
Stretch Injury
.
Advantages
. Supraclavicular approach gives the surgeon complete
access to the entire high cervical plexus and C5 to T1
roots;
the
spinal
nerves,
trunks
and
their
branches; the phrenic, dorsal scapular, long thoracic,
and suprascapular nerves; as well as the spinal acces-
sory nerve.
.
Complete access to the anterior and posterior divisions;
the lateral, posterior, and medial cords of the brachial
plexus and their branches; and to the musculocuta-
neous, subscapular, thoracodorsal, axillary, radial, ulnar,
median, lateral, and medial pectoral nerves
.
Disadvantages
.
It is difficult to visualize or obtain full access to the roots,
trunks, or branches of the brachial plexus, which lie be-
neath the clavicle or distal segment of the brachial
plexus, without extending the incision for infraclavicular
dissection.
. Anatomy
The brachial plexus is formed by the union of the ventral
rami of C5,C6,0, C8,and n. The supraclavicular portion of
the brachial plexus includes C5to n spinal nerves and the
three trunks of the plexus, whereas anterior and posterior
divisions lie beneath the clavicle. Lateral, posterior, and
907

908
Peripheral Nerve: BrachialPlexus
Figure 122-1
Overview of the anatomy of the brachial plexus.
medial cords are infraclavicular,where they provide the ori-
gin of the major nerves of the upper extremity (Fig. 122-1).
The spinal nerve, or root of the plexus, begins as multiple
sensory rootlets from the dorsal root entry zone, and usu-
ally includes one motor rootlet from the spinal cord. The
dorsal root ganglion is located at the intraforaminallevel,
and both roots come together to form the spinal nerve. The
primary posterior branches go to the paraspinal muscles
and the large anterior branch contributes to the brachial
plexus.
The extraforaminal course of C5is along the lateral edge
of the anterior scalene muscle, where it unites with C6,
which runs between the anterior and middle scalene mus-
cles, to form the upper trunk of the plexus.
The dorsal scapular nerve arises from the proximal level
of C5, lateral to the contribution of the long thoracic nerve
near the foramen, and then pierces through the middle sca-
lene muscle to reach the deep surface of the levator scapu-
lae. The dorsal scapular nerve runs parallel with the dorsal
scapular artery along the medial border of the scapula to in-
nervate the rhomboids.
The long thoracic nerve arises from the dorsal surface of
C6close to the junction of the upper trunk and also receives
contribution
from C5 and C7. It runs posterior to the
brachial plexus. then descends laterally and distally into the
thoracic wall to innervate the serratus anterior muscle.
C5 also supplies a branch to the phrenic nerve, running
anteriorly to the brachial plexus on the lateral border of the
anterior scalene muscle. The subclavial muscle nerve arises
from the anterior surface of the upper trunk and passesan.
teriorly to the lower portion of the plexus, innervatingthe
subclavius.
The suprascapular nerve arises from the posterolateral
portion of the upper trunk and runs beneath the posterior
belly of the omohyoid. parallel to the suprascapular vessels,
running distally through the scapular notch to innervatethe
supraspinatus and infraspinatus muscles.
The C7 spinal nerve emerges from the posterior tothe
medial edge of the anterior scalene muscle to formthemid.
dIe trunk. The C8spinal nerve, combined with Tl, formsthe
lower trunk, which lies behind the subclavian arteryandon
top of the middle and posterior scalene muscles. Themid-
dle and lower trunks do not generate branches. Thetrunks
of the brachial plexus lie in the posterior cervical triangle
area, bounded by the posterior border of the sternomastoid
muscle. the anterior border of the trapezius, and thesupe.
rior border of the clavicle. The middle trunk is smallerin
caliber than the upper or lower trunks.
The vertebral artery originates
from the subclavian artery,
ascending anteriorly toward the lower trunk to enterthe
foramen transversarium
of C6. Small branches fromthis
vessel supply the spinal nerves and anastomose withspinal
cord vasculature.
Suprascapular
and transverse
cervicalar.
teries from the thyrocervical
trunk run laterally acrossthe
anterior
surface
of the lower plexus
and branches ofas-
cending
cervical
and deep
cervical
arteries
anastomoses
with vertebral arteries. Beneath the clavicle. each trunk sep-
arates, forming anterior and posterior
divisions.

122
SupraclavicularApproachto BrachialPlexusSurgery
909
. Objective
Toexpose and obtain direct access to the supraclavicular
portionof the brachial plexus, including spinal roots or
nerves,trunks and their branches for the purpose of neurol-
ysis,direct end-to-end
suture or graft repairs, or nerve
sheathtumor resection
. SurgicalTechnique
Anesthesiaand Positioning
Becausebrachial plexus surgery requires extensive opera-
tivetime, general anesthesia is recommended. The neuro-
muscularblockade used for induction must wear offduring
theearly phase of the dissection so that intraoperative elec-
tricalrecording of the effects of muscle contraction from
stimulation can be tested. Local anesthetic
should be
avoideddue to the possibility of nerve conduction block,
whichmay cause errors in recording intraoperative nerve
action.
Thepatient is placed on the operating table in a supine
positionwith the head resting on a circular roll,away from
theside of the lesion. The patient's shoulder and clavicleare
broughtforward by placing a small roll or bolster behind
the scapula on the ipsilateral side. The head of the bed
shouldbe elevated 20 degrees, creating a semiseated posi-
tion,to decrease bleeding into the operative field (Fig.
122-2).
Theentire upper extremity of the patient's surgical side
shouldbe prepped and draped free and the patient's arm
extended onto a board at the side of the operating table.
./
.-
Figure122-2
Surgical positioning
and incision marking for the
supraclavicular
approachto the brachial plexus.
Thesurgeonshouldbe able to manipulate the position of
the arm to improve surgical exposure. Both lower extremi-
ties need to be prepped for possiblesural nerve graft har-
vesting. Placement of tourniquets around the extremities is
seldom required. Meticulous hemostasis can be achieved
through the use of the bipolar cautery throughout the dis-
section. The prolonged use of tourniquets can cause further
ischemic tissue or nerve injuries to an already compro-
misedarm.
Incision
After the site is marked with crosshatch lines, a no. 10 blade
is used to make an oblique incision along the posterior bor-
der of the sternocleidomastoid
muscle toward the medial
portion of the clavicle.The incision curves parallel along the
clavicle toward the proximal part of the deltopectoral
groove.The marked line should also extend below the clavi-
cle, toward the axillary crease, if it becomes necessary to
expose the infraclavicular portion of the brachial plexus.
Dissection
After the skin incision is made, a thin layer of platysma
muscle is encountered and sharply incised. The posterior
cervical triangle is bound by the posterior border of the
sternocleidomastoid muscle medially, the anterior border of
the trapezius muscle laterally, and the clavicle at the base.
After sharply incising the superficial investing fascia layer,
supraclavicular fat is dissected and pulled away laterally
from the posterior edge of the sternocleidomastoid muscle.
The branches of the supraclavicular cervical plexus and ex-
ternal jugular vein are identified and dissected laterally.
During dissection along the upper part of the posterior cer-
vical triangle, great caution must be taken to avoid injury to
the spinal accessory nerve where the nerve emerges from
just abovethe midpointofthe posteriorborderofthestern-
ocleidomastoid muscle. The posterior belly of the omohyoid
muscle is divided and pulled laterally after it is tagged with
sutures for later approximation. As the posterior cervical
triangle fat is dissected from the edges of the sternocleido-
mastoid muscle and clavicle, the transverse cervical artery
and vein, which cross the plexus, can be seen, ligated, and
divided (Fig.122-3).
When the sternocleidomastoid muscle is retracted medi-
ally, the phrenic nerve can be identified as it runs along the
superolateral border on the surface of the anterior scalene
muscle. The phrenic nerve is an important landmark for lo-
cating the (5 spinal nerve, which unites with (6 to form the
upper trunk of the brachial plexus. The nerve stimulator, set
at 1 mA,can be used to stimulate the phrenic nerve, causing
contraction of the ipsilateral hemidiaphragm. The phrenic
nerve is dissected and mobilized medially with a vascular
loop around the nerve so that the upper trunk can be dis-
sected.
Another helpful anatomical landmark is identification of
the transverse cervical rami. It emerges from the posterior
border of the sternocleidomastoid muscle, loops around it,
and can be traced proximally to identify (4 inferiorly to the
(5 spinal nerve.

Sternocleido-
mastoid
Levator
scapulae
.
.;',# "
,
Scalenus
medius
,.
-r---;r-
~
B,
'
,
'
"
"
C5 rool
~.
C6 root
, ..
Phrenic N.
.~ ~~
.
"
,Superior
belly
,
of omohyoid
1..:
Scalenus anticus
910
Peripheral Nerve: BrachialPlexus
Trapezius
Ext. jugular V.
Suprascapular
N.
Inferior belly of
omohyoid
Upper trunk (UT)
Clavicle
Proximal dissection of the CSnerve often requires the re-
section of the transverse process with a high-speed drill or
with a no. 2 Kerrison punch. Venous plexus around the
spinal nerve close to the foramen requires meticulous he-
mostasis with bipolar use of Gelfoam with thrombon or
Surgicel. Special attention is required during dissection of
CS at the foramen to avoid injuring the dorsal scapular
nerve, which originates from the posterior aspect ofCS,lat-
eral to the small branch given off of it, to form the long tho-
racic nerve.
The long thoracic nerve arises from the dorsal surface of
the C6 spinal nerve with contributions from CS and C7.It
pierces through the middle scalene muscle and runs poste-
rior to the brachial plexus and continues inferiorly to inner-
vate the serratus anterior muscle in the chest wall.
The nerve to the subclavius arises from the anterior as-
pect of the upper trunk. This nerve has no clinical signifi-
canceexcept it is the origin of the phrenic nerve.
During dissection along the posterolateral aspect of the
upper trunk, the suprascapular nerve can be identified and
isolated from the upper trunk. It runs toward the scapular
notch. level with the clavicle and the suprascapular artery
and vein.
The C7spinal nerve emerges from between the anterior
and middle scalene muscles inferior to CS and C6 spinal
nerves. Toimprove exposure of the proximal middle trunk
and C7spinal nerve, the anterior scalene muscle is often re-
sected while protecting the phrenic nerve.
The C8 and n spinal nerves are located posterior to the
subclavian artery. The lateral portion of clavicular insertion
of the sternocleidomastoid
muscle is detached from the
clavicle,and retraction of the subclavian artery inferiorly by
using a vein retractor can further expose C8, n, and the
lower trunk (Fig. 122-4). Resect the anterior scalene mus-
Transverse
cervical
A.
Figure 122-3
Surgical dissectionofthe
posterior
cervical
triangle,
which is boundee
by the
posterior
border
of the sternocleido-
mastoid
muscle
medially,
the anterior borde
of the trapezius
muscle
laterally, and the ciai'!'
cle at the base.
cle, excise the Sibson's, and mobilize the subclavianartery
by using a Penrose drain looped around the artery.Special
caution
must
be taken
when
dissecting
around the 11
spinal nerve to prevent injuries to the vertebral artery,cer.
vicothoracic
ganglion (stellate ganglion), apex of pleura,and
thoracic duct in left-side dissection.
If the surgeon inadver.
tently enters
the pleura during
dissection
of the T1spinal
nerve, the pleura can be repaired
with 4-0 silk suturesand
controlled
ventilation
by an anesthesiologist.
Plan toobtain
an intraoperative chest x-ray in the operating roomafter
closure for chest tube placement if there is significantpneu.
mothorax.
There are no nerve branches originating fromthemiddle
or lower trunks in the supraclavicular
region. The clavicleis
dissected
circumferentially
by isolating both the subclavius
muscle and the vessel beneath
the clavicle. The segmentof
the subclavius
muscle and vessel are ligated and resected.
A moistened
sponge
gauge
is placed
around
the clavicle
and clamped
with a large hemostat,
which can be usedto
pull the clavicle inferiorly, giving a better view ofthestruc.
tures underneath the clavicle. Anterior and posteriordivi.
sions from three trunks are located under the clavicle.
Donor Nerve Graft Harvesting
The most common source of donor nerve grafts are the
sural nerves from both lower extremities. Alongitudinalin.
cision is made at ankle level between the Achillestendon
and medialmalleolustowardthe poplitealfossa,thenalong
the posterior calf where it lies subcutaneously. Theentire
length of the sural nerve can be harvested as it generally
from peroneal nerve.Anaverageof 25 to 35 cmlengthof
sural nerve can be harvested from each leg.

......,,~
i
122
Supraclavicular Approach to BrachialPlexus Surgery
911
Omohyoid
Suprascapular
N.
Scalenus medius
External
jugularV.
---LUT
--."
..
I
MT
Clavicle_
. SurgicalRepair
Laceration
Transectionor acute laceration injuries to the plexus are
bestrepairedimmediately while exploration and repair is
mostprudent.
Acuteexploration
and direct
end-to-end
suture
repair
(neurorrhaphy)of supraclavicular
brachial
plexus injuries
thatare a result
of sharp
laceration
have very favorable
functionalsurgical outcomes.
If bluntly transected
injuries
frommotorblades or chain saws are observed during acute
explorationfor vascular
repair,
each stump
needs
to be
tackeddownto the adjacent soft tissue. This will maintain
thelength of the lesion
and minimize
the length
of any
nervegrafts that may be required
after resection
of both
endsofthe nerve stumps
until healthy fascicles can be ob-
servedinsubsequent surgeries
Penetrating/GSW
Mostpenetrating injuries. like G5W,produce complete or
incompletelesions. Asmall number result in total physi-
caldisruption.If no signs of reinnervation
are seen after
severalmonths, exploration and intraoperative nerve ac-
tionpotential(NAP)should be performed and recorded.
Externalneurolysis is performed only if NAPis recorded
across
thelesion.Ifno NAPis recorded, a segment ofthe
lesionis resected and repaired with direct end to end
suturerepair, or more frequently, nerve graft repair is
necessary.
IT
Scalenus anticus
Subclavian A.
Transverse
cervicalA.
Figure 122-4
Exposureofthe upper (UT),
middle (MT), and lower (LT)trunks and
suprascapular nervethrough the supraclavic-
ularapproach.
Stretch Injury
Most stretch or traction injuries do not avulse or pull the
plexus elements away completely. Most injuries are lesions
in continuity, along with severe internal disruption and for-
mation of the neuroma mass. The dissection should be ex-
tended proximally and distally to the injured nerve seg-
ment, as well as to other neural elements of the brachial
plexus, so as to understand the extent of the injury and its
relationship to the surrounding anatomy. It is essential that
the surgeon record intraoperative NAPacross the lesion to
determine internal fascicular disruption and to assess the
extent of axonal regeneration.
Because spontaneous recovery may be expected, lesions
in continuity with positive NAPshould not be resected after
external neurolysis is performed to free the nerve from the
surrounding dense fibrotic scar tissue.
Largeneuromas, combined with the absence of NAP,indi-
cate internal disruption of fascicles.These are resected with
a sharp no. 15 blade until healthy-appearing fascicular pat-
terns are observed on the cross sections of both nerve
stump ends (Fig. 122-5). Nylon sutures (8-0 or 9-0) are
used to perform interfascicular graft repair. It is essential
that proper decisions are made as to which proximal lead-
out grafts go with what distal segments. Determining the
number of nerve grafts to be used and their proper lengths
will minimize tension at the repair sites and are also impor-
tant factors to keep in mind. The length of the nerve gap can
be shortened by mobilizing the nerve. This is done by
extending dissection of the nerve longitudinally along the
nerve, joint mobilization, and nerve transposition, which
provides a more direct route to the nerve.

912
Peripheral Nerve: BrachialPlexus
A
B
Most stretch injuries of the supraclavicular
brachial
plexus cannot be repaired by direct suture repair. Autolo-
gous interfascicular nerve grafts are required to repair the
gap, after resection of the nonrecordable NAPportion of the
nerve (Fig.122-6).
Ifavulsed spinal nerves are identified, proximal dissection
at the foramen levelis necessary so that the surgeon may find
a potentiallead-out stump for possiblenerve graft repair.
Figure 122-5
(A) Surgical dissection
of the lesion in continuitywith
neuroma formation
in the upper trunk. (8) Sharp resection oftheneu-
roma until normal-appearing
fascicles are observed
in both proximal
and distal stumps.
If complete spinal root avulsion occurred, and proximal
lead-outs cannot be established for direct nervegrafting,
then neurotizationusingdescendingcervicalplexus,distal
spinal accessory nerve, or intercostal nerves to musculocu.
taneous nerve is required.
Surgeons must be prepared to extend their exploration
into the infraclavicular brachial plexus to obtain adequate
access when it is necessary.
L

122
SupraclavicularApproachto BrachialPlexusSurgery
913
Figure 122-6
Interfascicular sural graft
repair from proximal stumps of (5 and (6 to
anterior divisions.
References
1. KlineDG.Hackett ER.Happel LH.Surgery for lesions of the brachial
plexus. Arch NeuroI1986;43:
170-181
2.
Kline DG. Perspectives
concerning
brachial
plexus
injury and repair.
Neurosurg Clin N Am 1991 :2:151-164
3.
Lusk MD. Kline DG. Garcia CA.Tumors ofthe
brachial
plexus. Neuro-
surgery
1987:21 :439-453
4.
Kline DG. Hudson AR.Nerve Injuries: Operative Results for Major Nerve
Injuries.
Entrapments.
and Tumors. Philadelphia:
WB Saunders;
1995

123
Infraclavicular Approach to
Brachial Plexus Surgery
Daniel H. Kim, Steven D. Chang, and David G. Kline
.
Indications
.
Contraindications
.
Advantages
.
Disadvantage
.
Objective
Infraclavicular brachial plexus injury is most commonly
caused by stretch injuries; contusive injuries to the cords;
cords to nerve lesions with associated axillary artery in-
jury; shoulder dislocation or fracture; and humeral frac-
ture.
Infraclavicular stretch injuries
may often spare
shoulder function, but damage extends from divisions of
the cords to more distal nerves.1.2Isolated axillary palsy
associated with injuries to cords or cords to nerves is also
common. With the the infraclavicular approach the sur-
geon has complete access to the anterior and posterior di-
visions; the lateral, posterior, and medial cords of the
brachial plexus and their branches; and the musculocuta-
neous, subscapular, thoracodorsal, axillary, radial, ulnar,
median, lateral, and medial pectoral nerves.1.2.3
.
Indications
.
Tractioninjury(motorcycle,automobile,sports,orwork
related)2.3
.
Lacerationinjury(sharpknifeor glass,or blunt transec-
tion from propellers or chain saws )2.3
.
Contusiveinjury(associatedshoulder or humeral frac-
tures)
.
Penetratinginjuryfromgunshotwound(GSW)or metal
fragments2.3
.
Iatrogenic injury (head and neck, shoulder orthopedic
surgeries)
.
Compression injury
.
Injection injury (regional anesthesia)
.
Nerve sheath tumor, metastatic tumort
.
Radiation injury
914
. Anatomy
.
Surgical Technique
Anesthesia and Positioning
Incision and Dissection
Surgical Repair
.
Contraindications
. Brachialplexitis
.
Transient radiation plexopathy
.
Advantages
.
Complete access to the anterior and posterior divisions
ofthe brachial plexus
. Good exposure
of the lateral, posterior, and medial cords
.
Ability to visualize the cord branches including from
proximally to distally; the lateral cord's lateral pectoral
and musculocutaneousnerves;the posteriorcord'stho-
racodorsal, subscapular, axillary, and radial nerves;the
medial cord's ulnar nerve; and the lateral and medial
cord's formation of the median nerve
.
Complete access to the entire high cervical plexusandCS
to T1 roots; the spinal nerves, trunks, and their branches:
the phrenic,dorsalscapular,longthoracic,and supras-
capular nerves; as well as the spinal accessory nerve
.
Disadvantage
.
Difficultto visualize or obtain full access to the roots,
trunks, or branches of the brachial plexus without ex-
tending the incision supraclavicularly
.
Objective
Toexpose and obtain direct access to the infraclavicular
portion of the brachialplexus,includingdivisions,cords.
and
their
branches;
to
perform
neurolysis;
direct

123
InfraclavicularApproachto BrachialPlexusSurgery
915
end-to-end suture or graft repairs; or nerve sheath tumor
resection.
. Anatomy
Beneath the clavicle, each trunk separates
into anterior and
posteriordivisions. The anterior division contains fibers to the
flexormuscles or anterior surface of the arm or forearm, and
theposterior division distributes fibers to the extensor muscles
anddorsal surface of the upper extremities. The divisions of all
threetrunks help form the three cords of the brachial plexus.
The anterior divisions of the upper and middle trunks unite
toform the lateral cord, distal to the clavicle. The lateral cord is
thefirst neural element to be encountered during infraclavicu-
lardissection. It is situated
in the anterolateral
aspect of the
axillaryartery. The anterior division of the lower trunk contin-
uesto form the medial cord, which is medial to the axillary
artery.All posterior divisions of the three trunks unite to form
theposterior cord of the brachial plexus, which is situated be-
hind the axillary artery.3 Cords are named relative to their
proximityto the axillary artery at the pectoralis minor level.
The lateral cord runs in a medial to lateral direction
over
the artery
and terminates
to form the musculocutaneous
nerve after giving off a lateral contribution
to the median
nerve.The musculocutaneous
nerve descends into the biceps
and the brachialis
after supplying
branches
to the coraco-
brachialis muscle. The lateral pectoral nerve arises from the
lateral cord and sends a ramus to the medial pectoral nerve,
which forms a loop and penetrates
through the cIavipectoral
fasciato innervate the pectoralis major muscle.1.3
The posterior cord is situated deep behind the axillary
artery and gives off upper subscapular, thoracodorsal, lower
subscapular, axillary, and terminal branch radial nerves. The
upper subscapular nerve is a small branch that runs poste-
rior to the axillary artery and innervates the upper part of
the subscapular muscle. The thoracodorsal nerve emerges
between the upper and lower subscapular nerves and runs
in the posterior axillary wall, innervating the latissimus
dorsi muscle. The lower subscapular nerve innervates lower
part of the subscapularis and teres major muscles. The axil-
lary nerve generally arises from the posterior cord but can
also arise from the posterior divisions of the upper and
middle trunks. It runs anterior to the subscapularis muscle
and passes through the quadrilateral space, which is bound
above by the subscapularis and teres minor muscles, below
by the teres major muscle, medially by the long head of the
triceps, and laterally by the surgical neck of the humerus.
The axillary nerve innervates the articular shoulder joint,
the deltoid and teres minor muscles, and the skin overlying
the deltoid. The radial nerve is a large terminal branch of
the posterior
cord, which
runs inferiorly toward the
humeral groove and wraps around the humerus.l
The medial cord provides a major contribution to the me-
dian nerve, the medial brachial cutaneous nerve, the medial
antebrachial cutaneous nerve and its terminal branch, and
the ulnar nerve.3The medial pectoral nerve arises from the
medial cord and connects with the lateral pectoral nerve
through a communicating
100p.3 It divides into several
branches and innervates both pectoralis major and minor
muscles (Fig.123-1).
Figure123-1
Overview anatomy of the brachial plexus.

916
Peripheral Nerve: BrachialPlexus
.
SurgicalTechnique
Anesthesia and Positioning
Becausebrachial plexus surgery requires extensive operative
time, general anesthesia is recommended. The neuromuscu-
lar blockadeused for induction must wear offduring the early
phase of the dissection so that intraoperative electrical
recording and the effects of muscle contraction from the
stimulation maybe tested. Localanesthetic should be avoided
due to the possibility of nerve conduction block,which may
cause errors in the recordingof intraoperative nerve action.l3.4
The patient is placed supine on the operating table with
the head supported on a circular head rest. The patient's
clavicle is raised with a small bolster beneath the scapula
posteriorly. The affected upper limb is supported on an ex-
tended arm board in a 60 degree abducted position.
Incisionand Dissection
The surgical incision follows the deltopectoral groove, be-
ginning proximally at the clavicle and extending distally to-
ward the axilIary crease (Fig. 123-2). The lateral border of
the pectoralis major muscle is dissected from the clavicle
and split along the deltopectoral groove. The cephalic vein
(deltopectoral) is usually ligated as it crosses the axilIary
vein close to the clavicle.Afterthe subclavicular muscle and
vessel are dissected and ligated, the clavicle can be mobi-
lized and retracted superiorly by using a moistened sponge,
which is placed under and around the clavicle to expose the
infraclavicularportion of the brachial plexus.
After self-retaining
retractors,
such as an Adson,are
placed between
the deltoid and pectoralis
major muscles
along the deltopectoral
groove, the clavi pectoral fasciais
identified
and then divided to expose the origin ofthepec.
toralis minor muscle at the coracoid process. (Fig. 123-3
The tendon belonging
to the pectoralis
minor muscleisdi.
vided after it is tagged with two sutures on either sidefor
later approximation. Distal exposure is gained by elevating
and pulling the pectoralis
major muscle inferiorly on asling
with a sponge gauge to expose a broad expanse of the infra.
clavicular space.
The first neural element
the physician encounters isthe
lateral cord, which is created from contributions fromthean.
terior divisions of the upper and middle trunks, whichliesu-
perficial and lateral to the axilIary artery. The lateralcord
gives off the lateral
pectoral
nerve and branches intothe
musculocutaneous
nerve and lateral cord and contributesto
the median nerve. The musculocutaneous
nerve, a terminal
branch of the lateral cord, dives into the biceps and brachialis
after piercing and supplying the coracobrachialis muscle.
The posterior
cord is formed by the posterior divisionso!
all three trunks and lies posterior
to the axillary artery.The
posterior
cord gives off subscapular,
thoracodorsal, axillary.
and radial nerves. Several subscapular branches arise,usu.
ally from the posterior
cord or axilIary, and run inferiorly
and obliquely, innervating
the subscapularis
and teresma-
jor muscles. The thoracodorsal
nerve arises from the paste.
rior cord, innervating
the latissimus dorsi.
The posterior
cord then divides into its two major
branches,
the axilIary
and the radial
nerves. The axillary
nerve
dives down
into the quadrilateral
space, with the
Figure 123-2
Surgical positioning
and inci.
sion marking for the infraclavicular approachto
the brachial plexus.

123
Infraclavicular Approach to Brachial Plexus Surgery
917
DeltoidM.-+--
..' -
Lateral cord
Subclavian
A.& V.
_Clavide
Lateral pectoral N.
Thoracoacromial
A.
Pectoralis major
(partiallyreflected)
Figure123-3
Dissection along the deltopectoral
groove and incision of the clavipectoral fascia to expose the lateral cord gives off the lateral pec-
toralnerve and branches into the musculocutaneous
nerve under the pectoralis minor muscle.
posteriorhumeral circumflex vessel, innervating the deltoid
andteres minor muscles (Fig. 123-4). The terminal outflow
oftheposterior cord is the radial nerve, which runs inferiorly
towardthe humeral groove and winds around the humerus.
Averyimportant anatomical landmark is the medial relation
betweenthe radial nerve and the profundus branch of the
axillaryartery. This can be used to locate the proximal radial
anddifferentiate it from the more lateral axillarynerve.
Themedial cord is formed from the lower trunk, which
emergesbetween the axillary artery and vein. It gives off
themedial pectoral nerve; the medial brachial cutaneous
nerve;the medial antebrachial cutaneous nerve (a major
contribution to the median nerve, which wraps around
Deltoid
Lateral cord
AxillaryN. &posterior
circumflex humeral a.
inthe quadrangular space
" ·~J
~~
- .,.,,\
-'~
~I
.~
i
Musculocutaneous
N. ~'~
-
. .~t;--
'
Biceps brachii'
~
~
~_
Coracobrachialis ~
. .
r-
.
_.~.
.
~
~;~.
. .;
.,
<&,
...~
Median N.
'
MedialcutaneousN.~.,
a,(
offorearm
Latissimusdorsi
the medial and superior side of the axillary artery); and its
terminal branch, the ulnar nerve. These neural structures
remain medial to the brachial artery as they begin their de-
scent down the upper arm (Fig.123-5).
Ifthere is extensive scarring, exploration should begin as
far away distally as possible, to locate normal tissue before
proceeding proximally.3.4
Surgical Repair
Methods of recording intraoperative nerve action potential,
neurolysis, and direct end-to-end suture and graft repair
have been described in Chapter 122.
-
Suprascapular N.
\
~ ~
~'
.~
..
.
C5. C6 & phrenic N.
_
! Long thoracic N.
'"
".
C7
.'
-,
~~C8
. _~...}.
>~.
T1
-:~
'J
/'~
, ,
,
..
.
. ~"
. c
.
...
Postenor cord
,,~
.
.
Medialcord
RadialN.
Thoracodorsal
N.&A.
Figure 123-4
Exposure of the posterior cord. which lies posterior to the axillary artery and its branches: the subscapular. thoracodorsal,
axillary,
andradial nerves.

918
Peripheral Nerve: BrachialPlexus
Clavicle
Suprascapular
N.
Lateral cord
Thoracoacromial
A.
~ectoralis
minor
Subclavian
A.& V.
Lateral pectoral N.
Pectoralis
major
(reflected)
Medial pectoral N.
Medial cutaneous
N
of forearm
Figure 123-5
Exposure of the medial cord and its branches: the medial brachial and antebrachial cutaneous
nerves and ulnar nerve.
References
1.
Kline DG. Hackett
ER. Happel
LH. Surgery
for lesions
of the brachial
plexus.
Arch
NeuroI1986:43:170-181
2.
Kline DG. Perspectives
concerning
brachial
plexus
injury and repair.
Neurosurg
Clin N Am 1991 :2:151-164
3.
KlineDG. Hudson AR.Nerve Injuries: Operative Results for MajorNer"
Injuries.
Entrapments.
and
Tumors.
Philadelphia:
WB Saunders: 19"
4.
Lusk MD. Kline DG. Garcia CA. Tumors
of the
brachial
plexus. Neu~
surgery
1987:21
:439-453

124
SurgicalApproach to the Spinal
Accessory Nerve
StevenD. Chang, Daniel H. Kim, and David G. Kline
. Indications
. Contraindications
. Advantages
. Disadvantages
. Objectives
. Anatomy
Acommon cause of spinal accessory nerve injury is iatro-
genicdamageasa resultofsurgicaltraumato the posterior
cervicaltriangle region. such as lymph node biopsy, exci-
sionofneck tumor, or carotid endarterectomy. Other causes
ofspinal accessory nerve injury include traumatic stretch,
lacerations from knife or glass, and penetrating injuries
causedby gunshot wounds (GSW)or stab wounds.! Injury
to the spinal accessory nerve results in paralysis of the
trapeziusmuscle, causing inferior translation of the shoul-
der,occasional winging of the scapula, and pain in the
shoulder.Surgical correction becomes necessary.
. Indications
. Iatrogenic injury
. Stretchinjury (associated with shoulder and neck injury)
. Lacerationinjury
. Penetrating injury
. Contra indications
. Scapular winging not caused by a long thoracic nerve
palsy. In spinal accessory nerve (SAN) palsy, lateral
movement of the arm accentuates the winging; in long
thoracic palsy, pushing forward against resistance with
the arm extended forward produces winging.
.
Surgical Technique
Anesthesia and Positioning
Incision and Dissection
Neurolysis
Repair
Closure
.
Advantages
.
Frequentlyreducespain and improvesshoulderabduc-
tionevenin patientswith residualweakness
.
Disadvantages
. Recovery is not perfect.
.
Although shoulder shrug often recovers, some winging
ofthe scapula and lack offull abduction often remains.
.
The shoulder on the affected side versus the contralat-
eral frequently is carried at a lower level.
.
Objectives
Toexpose and obtain direct access to the SANas it emerges
from the sternocleidomastoid
muscle (SCM) to innervate
the trapezius muscle, to perform neurolysis, direct suture,
or nerve graft repairs
. Anatomy
TheSANis formedwith cranial rootlets fromthe medulla
and from cervical rootlets from the first through sixth
cervicalsegments.It exitsthroughthejugular foramenand
919

920
Peripheral Nerve: BrachialPlexus
descends between the internal carotid artery and jugular
vein into the posterior stylohyoid muscle and diagastric
muscles. piercing the SCMas it innervates the muscle. The
SCMis also innervated by branches from C2. C3, and C4
such that even if there is complete SANinjury, it does not
produce paralysis to the SCM.The SANemerges from the
posterior border of the SCM.4 cm below the tip of the mas-
toid process. or just above the midpoint of the SCMat its
length from the mastoid eminence to the clavicle.
The nerve enters the posterior cervical triangle of the
neck. bound by the anterior border of the trapezius muscle
laterally, the clavicle as its base. and the posterior border of
the SCMas the medial border.
The great auricular nerve loops around the lateral border
of the SCM as it ascends superiorly. The SAN always
emerges superior to the great auricular nerve,alongtt,
SCM.
Often C2, C3, and C4 give branches
to the SANasitdt-
scends to innervate
the trapezius
muscle, but the trapezi~
muscle is predominantly
innervated
by the SAN.
The SAN descends
obliquely along the anterior surface"
the levator scapulae muscle and passes through theposten
cervical triangle fat, lymphatic chain. and dense fascia.then
gives off several branches
as it passes underneath theant~
riar border of the trapezius
muscle (Fig. 124-1 ).Inthis~
terior cervical triangle.
the SAN is covered only bytheS~I"
and the investing cervicalfasciaofthe neck.whichmakes the
SANvulnerable to operative injury.Thecervicallymphnode~
often lie beneath
the path of the SAN.making the nervew,
nerable during cervical lymph node biopsy procedures.
- -- --~
--"
(
Figure 124-1
Overview anatomyofthe
spinal accessory nerve in posterior cervi-
cal triangle.
....
' -
,
I
/'

124
Surgical Approach to the SpinalAccessory Nerve
921
. Surgical Technique
Anesthesia and Positioning
Generalanesthesia is recommended. The neuromuscular
blockadeused for induction
must wear off during the early
phase of the dissection
so that
intraoperative
electrical
recording and the effects of muscle contraction
from stimu-
lationmay be tested. Local anesthetic should be avoided
dueto the possibility
of nerve conduction
block, which can
causeerrors while recording intraoperative
nerve action.
The patient
is situated
on the operating
table in a semi-
seated position with the head on a horseshoe
headrest,
fac-
ingaway from the side of the lesion.
Incisionand Dissection
Priorto making any incision, the surgeon must be able to
visualizethe course of the SAN,utilizing surface anatomical
landmarks.The SANemerges from the posterior border of
theSCMat the level just above the midpoint, between the
mastoideminence and the clavicle. It then runs obliquely
andinferiorlytoward the tip of the shoulder.
Anoblique skin incision is made from the midpoint of the
posterior margin of the SCMto the anterior border of the
trapeziusmuscle (Fig. 124-2). Ifa horizontal surgical inci-
sionhas been established from prior surgery, make a verti-
callimb incision through it to expose the lateral border of
theSCMand the anterior border of the trapezius muscle.
/
\
Figure 124-2
Surgical incision for the spinal accessory nerve expo-
surein posterior cervical triangle.
Figure 124-3
Dissectionalong the posterior border of the stern-
ocleidomastoid muscle to identify the transverse cervical and great
auricular nerves.
During the initial dissection along the posterior border of
the SCM,identify the transverse cervical and great auricular
nerves as they curve around the SCM(Fig. 124-3). They are
important surgical landmarks to help locate the SANas it
emerges within 1 to 2 cm superior to these nerves. Make a
sharp dissection using Metzenbaum scissors to identify the
proximal and distal stumps within the fibrous fatty subcu-
taneous tissue.
The dissection should be carried through from the nor-
mal proximal or distal segment of the injured nerve, then
extend carefully toward the main pathology.1Anerve stim-
ulator can be used to localize the proximal nerve stump by
observing contraction ofthe SCM.
The difficulty of this operation is locating the distal
stump ofthe SAN;thus the surgeon must use caution dur-
ing the dissection to preserve the nerve branches that are
encountered
along the anterior border of the trapezius
muscle.
The proximal and distal stumps are prepared in the stan-
dard fashion after appropriate electrophysiological evalua-
tions are performed.
Neurolysis
Ifa lesion in continuity is found, external neurolysis is per-
formed along the nerve and nerve action potential (NAP)is
recorded across the lesion. If NAPcan be recorded across
the lesion, then the patient has a good prognosis for func-
tional recovery.

Repair
922
Peripheral Nerve: BrachialPlexus
Ifsharp transection is identified during the surgery, direct
end-to-end suture repair of the transected stumps can be
achieved by using 9-0 nylon sutures. But most frequently
performed cases on SANinjuries are delayed operations.
wherein the nerve gap is present from the defect where di-
rect end-to-end suture repair is often impossible. In these
cases. both proximal and distal stumps are identified and
trimmed until healthy-appearing
fascicles are seen and
then the nerve graft repair is performed to reestablish con-
tinuity (Figs. 124-4 and 124-5). The great auricular nerve
can be used as a donor nerve. as can the sural nerve.
Closure
APenrose drain is used as the gravity drain. without using a
closed suction system, to prevent accidental disruption of
graft repair while pulling the drain postoperatively.
After subcutaneous and skin closure, an arm sling is used
to support the shoulder for 3 weeks. after which passive
range-of-motion exercises may be started.
Trapezius
Splenius capitis
Lesser occipital
N.
Levator scapulae
Accessory
N.
Scalenus medius
Supraclavicular Ns.
Reference
1. Donner TR. Kline DG. Extracranial spinal accessory nerve injury.
Neurosurgery
1993;32;907-911
Figure
124-4
Proximal and distal stumps are identifiedand
trimmed
until healthy-appearing
fascicles are seen.
Greater auricular N.
Sternocleido-
mastoid
Cervical
plexus
Ext. jugular V.
Omohyoid
Clavicle
Figure 124-5
Interfascicular sural nerve
graft repair of the spinalaccessory
nerve.

125
SurgicalApproach to the Axillary Nerve
StevenD. Chang, Daniel H. Kim,and David G. Kline
. Indications
. Contraindications
. Advantages of Anterior Approach
. Disadvantages of Anterior Approach
. Advantages of Posterior Approach
.
Disadvantages of Posterior Approach
.
Objectives
Themost common causes of axillary nerve injury are stretch
orcontusive injury associated with a humoral neck fracture,
shoulderdislocation, or a sharp upward blow directly under
thearmpit. Isolated axillary injuries can occur but usually
occurin conjunction with a diffuse injury to the infraclavic-
ularbrachial plexus. Other mechanisms of axillary nerve in-
jury include laceration, gunshot wound (GSW),and com-
pression(quadrilateral space syndrome ).1-3Paralysis of the
deltoidmuscle resulting from axillary nerve injury creates
subluxationof the glenohumeral joint and significant loss of
shoulder abduction. Because of the relatively short time it
takes for target muscles to reinnervate, favorable surgical
outcomes may be anticipated, even after nerve graft repair.
Ifthere is no significant functional return within 3 to 4
months,further surgical exploration isindicated.
.
Indications
. Stretch/contusive injury
. Laceration
. Penetrating injuries
. Iatrogenic injury (orthopedic operations)
. Compression injury
. Injection injury
. Nervesheath tumor
.
Contraindications
. Brachialplexitis
. Transient radiation plexopathy
. Anatomy
.
Surgical Technique
Anesthesia and Positioning
Incision and Dissection: Anterior
Incision and Dissection: Posterior
Decompression/Neurolysis
Suture Repair
Graft Repair
Closure
.
Advantages of AnteriorApproach
. Good exposure of the origin of the posterior cord and
the thoracodorsal and subscapular branches
.
Disadvantages of Anterior Approach
.
Difficultyofexposureofthe distal portion ofthe nerve
enteringthe quadrilateralspace
.
Advantages of Posterior Approach
.
Excellentdelineationofthe distalaxillarynerve
.
Disadvantages of Posterior Approach
.
Difficultyin tracing the damaged portion of the nerve to
more healthy proximal tissue within the posterior cord
in some patients
.
Objectives
Toexpose and obtain direct access to the proximal part of
the axillary nerve as it arises from the posterior cord at
infraclavicular brachial plexus for neurolysis, direct suture,
or nerve graft repair
923

924
PeripheralNerve:BrachialPlexus
. Anatomy
In most cases, the axillary nerve arises from the posterior
cord of the brachial plexus, lateral to the radial nerve, but in
some cases it arises from the posterior divisions from upper
or upper and middle trunks. The axillary nerve runs obliquely
A
B
and laterally along the anterior
surface of the subscapular
muscle with the posterior
circumflex
humeral vesseland
contains fibers from (5, (6, and minimal contributions from
C7,and exits the axilla through the quadrilateral space.
The quadrilateral
space is superiorly bounded by thesub-
scapularis
and teres minor, inferiorly bounded by theteres
Figure 125-1
Overview(A)anterior and (B)posterior anatomyofthe
axillary nerve.

125
SurgicalApproachto the Axillary Nerve
925
major,medially
bounded
by the long head of the triceps,
andlaterally bounded
by the surgical neck of the humerus.
The axillary nerve then divides into two major branches.
Thefirst first branch innervates the teres minor muscle, which
usuallyemerges within the quadrilateral space, but in some
casesit can arise prior to entering
the quadrilateral
space,
then it innervates
the posterior
deltoid muscle and covers
sensation to the lower part of deltoid region, where it contin-
uesto form the upper-lateral
brachial-cutaneous
nerve. The
secondbranch travels with the posterior circumflex humeral
vesselaround the humeral neck to innervate the anterior and
middledeltoid muscles. The axillary nerve also gives a branch
tothe capsule of the shoulder joint (Fig. 125-1).
. SurgicalTechnique
Anesthesia and Positioning
General anesthesia
is recommended
because brachial
plexussurgery requires extensive operative time. Preopera-
tively,the surgeon needs to advise the anesthetist that the
neuromuscular blockade used in induction must wear off
duringthe early phase of the dissection so that intraopera-
tiveelectrical recording, as well as the effects of appropriate
musclecontraction from the stimulation, may be tested.
Localanesthetic should be avoided due to the possibility of
nerveconduction block, which may cause errors in record-
ingthe intraoperative nerve action.
The patient is positioned in a lateral decubitus position
withthe affected side up. The patient's head is placed on a
horseshoe holder, and the entire shoulder and upper ex-
tremity of the surgical site should be prepped, draped free,
andplaced along the patient's side. The surgeon should be
ableto manipulate the position of the arm to improve surgi-
calexposure. The patient's leg is prepped for possible sural
nervegraft harvesting.
Incision and Dissection:
Anterior
Thesurgicalincisionfollowsthe deltopectoralgroove,be-
ginningproximally at the clavicle and extending distally to-
ward the axillary crease (Fig. 125-2). The lateral border of
the pectoralis major muscle is dissected from the clavicle
andsplit along the deltopectoral groove. The cephalic vein
(deltopectoral vein) is usually ligated as it crosses the axil-
laryvein close to the clavicle.Afterthe subclavicular muscle
andvessel are dissected and ligated, the clavicle can be mo-
bilized and retracted
superiorly by placing moistened
sponges under and around the clavicle, exposing the infra-
clavicularportion of brachial plexus.
After self-retaining
retractors, such as an Adson, are
placed between the deltoid and pectoralis major muscles
along the deltopectoral groove, the clavipectoral fascia is
identified and divided to expose the origin of the pectoralis
minor muscle at the coracoid process. The tendon belong-
ing to the pectoralis minor muscle is divided after it is
taggedwith two sutures on either side for later approxima-
tion.Distal exposure is then gained by elevating and pulling
the pectoralis major muscle inferiorly for exposing a broad
expanseof the infraclavicular space.
_/
Figure 125-2
Surgical incision for the anterior exposure of the axil-
lary nerve.
The first neural element encountered in this procedure is
the lateral cord created from contributions of the anterior
divisions of the upper and middle trunks, which lie superfi-
cially and laterally to the axillary artery. The musculocuta-
neous nerve is dissected and protected as it arises from the
lateral cord. The axillary artery is then dissected and mobi-
lized inferiorly with the vein retractor.
At the level of the coracoid process, axillary and radial
nerve branches from the posterior cord can be seen. Dissec-
tion should follow the axillary nerve as it runs along the
anterior aspect of the subscapular muscle into the quadri-
lateral space (Fig.125-3).
The most damaged segment of the axillary nerve's stretch
injury should be identified proximally before entering the
quadrilateral space. Dissection should occur proximally into
the infraclavicular portion of the brachial plexus to evaluate
the extent of the injury.
Incision and Dissection: Posterior
Exposure to the quadrilateral space from the posterior ap-
proach is done by tilting the patient anteriorly. The prepped
arm is then brought forward across the chest to expose the
posterior shoulder so that access to the distal axillary nerve
may be achieved.
An incision is made along the posterior border of the del-
toid muscle from the spine of the scapula and extends to-
ward the posterior axillary fold. It is often unnecessary to
detach the lateral half of the posterior deltoid muscle, due
to atrophy of the deinnervated deltoid muscle, which can
easily be retracted for better exposure. As the surgeon
dissects along the teres minor, the quadrilateral space and
axillary nerve with posterior humeral circumflex artery can
be identified (Fig. 125-4).

926
Peripheral Nerve: BrachialPlexus
Figure 125-3
Exposure of the axillary nerve as it branches off from the posterior cord and enters into the quadrilateral space.
Axillary N.
Phrenic N.
Transverse
cervicalA.
UT
Omohyoid
LT
MT
Slbclavian
A. &V.
Lateral cord
S,-"rascapular
N. &
vessels
Thoracoacromial
A.
Thoracodorsal
N.
& vessels
Musculocutaneous
N.
Deltoid
Biceps brachii
Tendon of
latissimus dorsi
Figure 125-4
Posterior of the quadrilateral
space to expose the axillary nerve and poste-
rior humeral circumflex artery.lAQ4)

Decompression/Neurolysis
125
SurgicalApproachto the Axillary Nerve
927
Ifscartissue is encountered during the exploration of the
axillarynerve, external neurolysis and mobilization of the
nerveare performed. Stimulating and recording electrodes
arethen used to measure nerve action potential (NAP)
acrossthe lesion. If positive
NAP is recorded,
neurolysis
is
usuallysufficient for favorable recovery.
SutureRepair
Iftransectionof the axillary nerve is recognized during the
surgery,then direct end-to-end
suture repair is possible,
butit is frequently
difficult
to obtain secondary
suture
re-
pairwithout significant tension at the suture repair site as a
resultof retraction
at both ends of the nerve stumps.
GraftRepair
Discontinuous lesions require nerve graft repairs to reestab-
lishcontinuity between
the proximal and distal nerve
stumps.Generally, a sural nerve is used as the donor nerve.
Thelength of the nerve grafts are measured
to avoid suture
References
1. Friedman AH, Nunley JA. Urbaniak JR. et at. Repair of isolated axillary
nerve lesions
after infraclavicular
brachial
plexus
injuries:
case re-
ports. Neurosurgery
1990;27:403-407
2. McKowen He. Voorhies RM. Axillary nerve entrapment
in the quadri-
lateral space: case report.J
Neurosurg
1987;66:932-934
repairs from the tension, which can lead to poor results. If
neuroma in continuity is encountered,
NAP across the
lesion is recorded. IfNAPcannot be measured across the le-
sion, a sharp no. 15 blade is used to cut the injured segment
until healthy-appearing fascicle on the cross sections is ob-
served in both proximal and distal segments. Graft repair is
then performed to reestablish continuity. If the lesion ex-
tends through the quadrilateral space, then posterior expo-
sure is necessary to identify the distal extent of the lesion.
After preparation of the distal stump, the grafts are sutured
to the distal segment and then passed through the quadri-
lateral space from posterior to anterior. The posterior
incision is then closed and the operating table is rotated
posteriorly for better anterior exposure of proximal graft
anastomosis.
Closure
Thedetachedpectoralisminormuscleisreapproximatedto
the coracoid process, and then the deltopectoral groove is
closed in layers. Postoperatively, an arm sling is used to im-
mobilize the shoulder for 3 weeks and then passive to pro-
gressive range-of-motion therapy may be started.
3.
eoene
lN, Narakas AO. Operative
management
of lesions ofthe
axil-
lary nerve, isolated or combined
with other nerve lesions. etin Neurol
Neurosurg
1992;94(Suppl):S64-S66

126
The Musculocutaneous Nerve
Robert Tiel
. AnatomicalVariations
.
Indications
.
Surgical Technique
Positioning
Incision
Transpectoral Dissection
Closure
The musculocutaneous nerve is one of the two terminal di-
visions of the lateral cord, the other being the lateral cord
contribution to the median nerve. This division occurs un-
der cover of the pectoralis major muscle and usually distal
to the pectoralis medius muscle. It is the continuation of the
lateral cord after the contribution destined for the median
nerve is given off. It is a mixed sensorimotor nerve, which
contains anterior motor and sensory fibers from the ante-
rior divisions of the upper and middle trunks which them-
selves are derivatives of the first three cervical roots of the
brachial plexus: (5, (6, and C7(Table 126-1).
This nerve supplies three anterior muscles of the arm, the
coracobrachialis, the biceps, and the brachialis. The biceps
and the brachialis are major flexors of the elbow. The sen-
sory fibers will form the lateral antebrachial cutaneous
nerve as the nerve pierces the biceps fasciadistally.
.
AnatomicalVariations
Anatomical variations in the pattern and formation of the
musculocutaneous nerve do exist, are relatively common,
and may be quite confusing to the occasional operator.1.2
The most frequently encountered variations are summa-
rized in Table 126-2. Although the most common pattern is
that of a single branch from the lateral cord to the median
nerve, there often maybe multiple smaller communications.
In a similar fashion there may appear to be no communicat-
ing branches and a large lateral cord/musculocutaneous
nerve going into the coracobrachialis. In the latter case, the
communicating
branches to the median territory occur
more distally
in the
nerve between
the biceps
and
brachialis.
928
.
Indications
The musculocutaneous nerve is seldom injured in isolation
but
there
are
occasions
when
the
sole exposure of
this
nerve
is warranted.
These
indications
are listedir.
Table 126-3. More commonly the musculocutaneousnerve
is injured
in association
with other elements of the infra-
clavicular
brachial
plexus. Occasionally
it may be theonly
element
not to recover spontaneously.
Sharp lacerations
to the anterior
shoulder and proximal
arm and immediate
loss of function
in the distributionof
the musculocutaneous
nerve warrant acute explorationand
repair of the nerve.
In stretch and gunshot injuries that fail to showclinical
evidence of recovery within 3 to 4 months ofinjury,opera.
tion is indicated both to evaluate the damaged nervewith
nerve action potential
(NAP) recordings
and repair thein-
jury if indicated.3
Sometimes
the nerve is divided by a more blunt mecha.
nism whereby
the ends of the nerve are contused anda
clean margin of viable nerve cannot be reliably determined.
In these cases a delay of 2 to 3 weeks may be indicatedto
allow this demarcation
between
viable and nonviablenerve
to be determined.
Exposure of this nerve is also indicated for nerve transfer
operations to restore elbow function after root avulsionin.
juries. Depending upon the extent of root avulsionsand
donor nerve availability for transfer the donor nervedissec-
tion may vary; however, the exposure
of the musculocuta-
neous nerve will nerve be the same irrespective of donor
nerve.
This nerve may be involved with primary nerve sheathtu.
mors such as schwannoma, neurofibroma,and neurofi.
brosarcoma
for which operative removal is indicated aswell.

Table126-1
MusculocutaneousNerve
126
Musculocutaneous Nerve
929
TheMusculocutaneous
Muscles
NerveIsa Derivative of
Supplied
Sensory
(5,(6, C7
Upper trunk
and
middletrunk
anteriordivisions
lateralcord
Coracobrachialis Lateralantebrachial
Biceps
Cutaneousnerve
Brachialis
Table126-2
Variationsofthe MusculocutaneousNerve
Singlebranch from lateral cord to median nerve (usual)
Multiplecommunicating
branches from the lateral cord to the
mediannerve
Noapparent branches from the lateral cord to the median nerve
. Surgical Technique
Positioning
Generalanesthesia is used. Paralyzingagents are avoided, to
allowmuscle stimulation to be observed intraoperatively.
Short-acting paralytics
for induction and intubation
are pre-
ferred. The patient
is positioned
prone with the affected
armextended
on an arm-board.
The shoulder
is mildly ele-
vated with a folded
sheet
and the head is rested
upon a
foamcushion and turned
away (Fig. 126-1).
Incision
Alineis drawn starting at the proximal third of the clavicle
coursingjust above the axilla to a point in the middle ofthe
armat the end of the deltopectoral groove (Fig.126-1). The
skin incision is made and dissection
is carried down
throughthe subcutaneous fat to the depth of the pectoralis
majormuscle investing the fascia.
Transpectoral Dissection
Thedeep exposure starts with a muscle-splitting incision of
thepectoralis major muscle along the run of the fibers ex-
tending from the medial third of the clavicle to the pec-
Table 126-3
SurgicalIndicationsand Timingfor
MusculocutaneousNerveInjuries
Surgical Indications
Timing
Stab wounds,
sharp lacerations
Blunt lacerations
with loss of continuity
Stretch injury,
gunshot wound
Nervetransfersfor
root avulsions to
restore elbow flexion,
nerve sheath tumors
Acute
Delayed 2-3 Weeks
Delayed 3-4 Months
Nonacute
toralis tendon (Fig. 126-2). Along exposure is indicated to
achieve the maximum width allowable at the operative
depth. Acauterizing scalpel will minimize muscle distortion
by electrical stimulation and provide excellent hemostasis.
Bilateral angled retractors are then inserted and the muscle
is spread. Immediately underneath the pectoralis major will
lie the pectoralis minor, fat, the elements of the brachial
plexus, the axillary artery, and vein (Fig. 126-3A). The pec-
toralis minor muscle arises from the third through fifth ribs
and inserts upon the coracoid process, which at this time
may be directly palpated.
Figure 126-1
Thepatient ispositioned supine with the affected arm
extended and supinated on an arm board. The shoulder is elevated
with a folded sheet. Theskin incision is made from the proximal third
of the clavicle,abovethe axillaand terminating in the distal deltopec-
toral groove.

930
Peripheral Nerve: BrachialPlexus
Figure 126-2
The pectoralis major is divided parallelto its fibers
starting at their insertionat the proximalthird ofthe clavicleand con-
tinuingto the beginningofthe pectoralistendon.
The coracoid process is identified by palpation and the
distal border of the pectoralis minor muscle is dissected
from the surrounding fatty tissue. The most superficial and
lateral element of the brachial plexus is the lateral cord, and
this element is usually encountered first. With further dis-
section into the fatty tissue distal to the lateral border of the
pectoralis minor this element is circumferentially dissected
or neurolysed by either scissors or scalpel dissection. A
Penrose drain is placed around the element to assist in this
dissection of the backside of the nerve. The pressure of
manipulation is thereby distributed more evenly over the
nerve than with vessel loops or vein retractors. Often lateral
pectoral branches are identified, which when electrically
stimulated will cause contraction of the pectoralis major
muscle. These branches may be tracked backward to aid in
identification of this element if required. In an undamaged
nerve, a simple disposable nerve stimulator may be used on
a setting of 2 mAand will give a robust contraction of the
muscle. The lateral cord is dissected distally until it bifur.
cates into its two terminal divisions. The lateral branchwill
be the musculocutaneous and the more medial, thelateral
cord contribution to the median nerve. Deeperto thelateral
cord element will be the axillary artery, which willusually
be pulsatile
and pass under the lateral cord contributionto
the median nerve.
The musculocutaneous
nerve
usually
gives off a small
branch to the coracobrachialis muscle before enteringinto
the coracobrachialis
muscle.
Usually
this point of entry
into the muscle
will occur
proximally
to the pectoralis
major tendon. The thin portion of this tendon maybesplit
without subsequent
repair. Oftentimes a small retractor
such as an AIm or Heitz will assist in exposing the nerve
at this location
(Fig. 126-3A).
If dissection
is then inade.
quate, the pectoralis
major muscle will require lateraldis.
section
and mobilization,
the use of a pediatric
laparo-
tomy sponge,
and a large Kelly hemostat
to function asa
retractor.
Adequate
exposure
can be achieved
without
surgical
compromise
to satisfactorily
expose this branch.
ing (Fig. 126-38).
Ofcourse the pectoralis tendon may be dividedtofurther
facilitate
surgical
exposure.
If this is deemed
necessary.
tagging sutures are placed to facilitate reapproximation,the
tendon is cut, and each end is retracted
out of the operative
field.
The musculocutaneous nerve then enters the bodyofthe
coracobrachialis muscle. It will give one or two twigswhile
passing through the body of this muscle. There is character-
istically a small branch to this muscle in the first centimeter
or two of its division from the lateral cord. This fasciclecan
usually be sharply dissected with a small no. 15scalpelboth
into the body of the muscle as well as into the musculocu-
taneous nerve to allow greater mobilization of the nerve
without
risk of traction
injury. Similarly the musculocuta.
neous nerve and its lateral contribution
to the median
nerve may be split proximally
until crossing
fasciclesare
seen. This maneuver will allow greater mobilization ofthe
musculocutaneous
nerve with less traction
on connected
structures
(Fig. 126-3C).
On rare occasion
when
the nerve has been divided and
has retracted into the coracobrachialis
the fibers ofthis
muscle
will need
to be cut to uncover
the distal nerve.
The musculocutaneous
then runs between
the brachialis
and the biceps, giving branches to both heads of thebi.
ceps and the brachailis muscle. It then continues asthe
lateral antebrachial cutaneous nerve exiting lateral tothe
biceps tendon to provide cutaneous sensation to thelat-
eral forearm.
At this nerve may be inspected from its origin to the
point where it disappears into the coracobrachialis muscle.
NAPrecordings maybe undertaken and if indicated neu-
roma resection and either end-to-end repair or graftrepair

126
Musculocutaneous Nerve
931
'\
A
maybe undertaken.
Closure
B
Figure 126-3
(A) The lateral cord can be found distal to the lateral
edge of the pectoralis minor muscle and dissected distally exposing
branches to the coracobrachialis muscle and its division into the mus-
culocutaneous
nerve and the lateral cord contribution to the median
nerve. The musculocutaneous
nerve is mobilized with the gentle re-
traction
of a Penrose drain. The Aim retractor
will spread the pec-
toralis major muscle as the fibers converge upon the pectoralis major
tendon's
insertion into the humerous bone. (B) The pectoralis major
tendon
may be mobilized to facilitate more distal exposure
of the
musculocutaneous
nerve with
sponges
attached
to hemostats.
(C) The fascicles maybe split to allow easier, less traumatic
mobiliza-
tion of plexal elements. The branch to the coracobrachialis may be cut
back into both muscle and the musculocutaneous
nerve. In a similar
manner the division of the musculocutaneous
nerve from its lateral
cord contribution
and the fusion of the two divisions of the median
nerve
may be split to the
point where
branching
fascicles
are
observed.
Once the evaluation and repair of the nerve have been
achieved, all Penrose drains and retractors are removed.
Muscular bleeding is controlled by bipolar coagulation.
The pectoralis
fascia is reapproximated
with 2-0 re-

127
The Median Nerve
Robert Tiel
.
Indications
.
Surgical Technique
Positioning
Incision
Dissection
.
Brachial Exposure
Incision
CubitalExposure
Closure
The median nerve begins as the fusion of major branches of
the lateral and medial cords. As a consequence it carries
nerve fibers to and from all cervical roots with the excep-
tion of (5. It runs the entire length of the arm with only one
major bifurcation. In the forearm a major branch, the ante-
rior interosseous nerve, splits off and runs on the anterior
surface of the interosseous membrane to supply the flexor
pollicis longus, flexor digitorum profundus. digits two and
three, and finally the pronator quadratus.1,2It has no sen-
sory representation. The nerve then continues supplying
the extrinsic flexors of the wrist and hand until it passes
under the flexor retinaculum and into the hand where it
ramifies to supply the intrinsic muscles of the thumb. and
the first two interossei. It further provides palmar sensation
to the thumb. second, and third. and the medial half of the
fourth digit (Table127-1).
As a consequence of its distance the nerve may require
exploration at any point along its course. The surgical
932
exposure
of the median nerve outside the carpal tunnel can
be divided
into the following
regions:
pectoral.
brachial,
and cubital. Each has its particular
anatomy. which requires
special consideration.
.
Indications
.
Stab wounds
.
Sharp lacerations
.
Blunt lacerations
.
Stretch injury
.
Gunshot wounds
. Tumors

Table127-1
127
Median Nerve
933
TheMedian Nerve
Isa Derivative of
Muscles Supplied
Palmaraspect digits 1-3
and medial side of digit 4
e6, 0,
e8, T1, 4
Pronator
teres
Upper trunk
Middle trunk
Lower
tru
n k
Anterior
Interosseous
Branch
Flexor pollicis longus
Pronator quadratus
Digitorumprofundusdigits2,3
Lateral cord
Medialcord
Distal Median Nerve
Flexor digitorum superficialis
Palmaris longus
Flexor carpi radialis
Intrinsic Muscles
Abductor pollicis brevis
Opponens pollicis
Lumbricals digit 1 and 2
. Surgical Technique
Positioning
Thepositioning of the patient for a median nerve exposure
is the same irrespective
of the level of the operation.
Generalanesthesia is used. Paralyzingagents are avoided to
allowmuscle stimulation to be observed intraoperatively.
Short-actingparalytics for induction and intubation are pre-
ferred.The patient is positioned supine with the affected
armextended on an arm board. The shoulder is mildly ele-
vatedwith a folded sheet and the head is rested upon a
foamcushion and turned away (Fig.127-1).
Incision
Alineis drawn starting at the proximal third of the clavicle
coursingjust above the axilla to a point in the middle of the
armat the end of the deltopectoral groove (Figs. 127-2 and
127-3).The skin incision is made and dissection is carried
downthrough the subcutaneous fat to the depth of the pec-
toralismajor muscle investing the fascia(Fig.127-3).
Dissection
Thedeep exposure starts with a muscle-splitting incision of
thepectoralis major muscle along the run of the fibers ex-
tending from the medial third of the clavicle to the pec-
toralistendon. Along exposure is indicated to achieve the
maximumwidth allowable at the operative depth. Direct
Sensory
heat cautery using a cauterizing scalpel will minimize mus-
cle distortion by electrical stimulation and provide excellent
hemostasis. Bilateralangled retractors are then inserted and
the muscle spread. Immediately underneath the pectoralis
major will lie the pectoralis minor, fat, the elements of the
brachial plexus, the axillary artery and vein. The pectoralis
minor muscle arises from the third through fifth ribs and
inserts upon the coracoid process, which at this time may
be directly palpated.
The coracoid process is identified by palpation and the
distal border of the pectoralis minor muscle is dissected
from the surrounding fatty tissue. The most superficial and
lateral element of the brachial plexus is the lateral cord, and
this element is usually encountered first with further dis-
section into the fatty tissue distal to the lateral border of
pectoralis minor. This element is circumferentially
dis-
sected or neurolysed by either scissors or scalpel dissection.
A Penrose drain is placed around the element to assist in
this dissection of the backside of the nerve. The pressure of
manipulation is thereby distributed more evenly over the
nerve than with vessel loops or vein retractors. Often lateral
pectoral branches are identified, which when electrically
stimulated will cause contraction of the pectoralis major
muscle. These branches may be tracked backward to aid in
identification of this element if required. In an undamaged
nerve a simple disposable nerve stimulator may be used, on
a setting of 2 mA,and will give a robust contraction of the
muscle. The lateral cord is dissected distally until it bifur-
cates into its two terminal divisions. The lateral branch will
be the musculocutaneous and the more medial, the lateral
cord contribution to the median nerve. Deeper to the lateral

934
PeripheralNerve:BrachialPlexus
Figure127-1
The patient ispositioned supine withtheshoul-
der elevated with a folded sheet ifa pectoral exposureisantici.
pated. The arm is extended and supinated. The pectoral exposure
uses the same landmarks as exposure of the musculocutaneous
nerve. The brachial exposure
starts
at the distal groove and
extends to a midarm level just above the cubital crease. Cubital
exposure starts above the cubital crease just medial to the distal
biceps. curves medially over the cubital crease and extendsdis-
tally down the midarm.
,
A
I
III.".
I I flff\
g/
\'\" \
B
Figure 127-2
(A) The median nerve is found by first dissecting the lateral card just beyond the pectoralis minor muscle. The lateral cord contribu.
tion is then followed until it joins the main body of the median nerve. The medial cord contribution
of the median nerve is then dissected distalto
proximal. Penrose drains are used to provide gentle retraction of neurolysed plexal elements. (8) The pectoralis major muscle seldom needs to bedi.
vided and may be mobilized with sponges attached to hemostats to facilitate exposure of the high median nerve at an axillary level.

127
Median Nerve
935
I\Cr
~ ~ ..
UI.,}
I,
Figure 127-3
The brachial exposure of the median nerve shows the
intimate association
of the brachial
artery
with the median
nerve as
well as the proximity
of the antebrachial
cutaneous
nerve and the ul-
narnerve with which it maybe sometimes
confused.
Distally the lacer-
tus fibrosis will need to be divided
to expose the distal median
nerve.
cordelement willbe the axillaryartery,whichwillusually
bepulsatile and pass under the lateral cord contribution to
the median nerve. The medially directed element is then
followeduntil it joins with the contribution from the me-
dialcord. At this juncture the median nerve is formed and is
distally followed as long as necessary in the arm to isolate
the pathology. This will usually entail its separation from
thebrachial artery.
Thepectoral exposure ofthe median nerve isa continuation
ofthe dissection of the lateral cord and musculocutaneous
nerve. As a consequence, anatomical variation in this area
must be appreciated to avoid confusion (Table 127-3). In
cases where there is no apparent lateral cord contribution
to the median nerve, dissection of the lateral cord must be
continued distally until such a communication is found,
which is on occasion below the pectoralis muscle tendon.
Once the lateral cord contribution to the median nerve is
identified, it is then neurolysed distally to its junction with
the medial cord contribution to the median nerve. This may
occur under cover of the pectoralis major or distally in the
arm. Once the median nerve is identified, the medial cord
contribution may then be identified and neurolysed by
more proximal dissection back up to its point of issue
Table 127-3
AnatomicalVariationsat the Pectoral Level
Single branch from the lateral cord to the median nerve (usual)
Multiple
communicating
branches from the lateral cord to the
median nerve
No apparent branches from the lateral cord to the median nerve
(Fig. 127-2) from the medial cord, which will be slightly
more posterior and medial to the axillary artery.
.
BrachialExposure
Incision
The initial incision for the brachial exposure of the median
nerve will start just distal to the insertion of the pectoralis
major muscle on the humerus bone and run in the palpa-
ble groove formed by the brachialis and triceps muscles
(Fig. 127-4). The median nerve will run in association
with the brachial artery, at first anterior and lateral, cross-
ing in the middle of the arm to a more medial position in
relationship to the artery as both nerve and artery con-
tinue into the cubital fossa. In the case of nerve trauma,
the presence of scarred tissue and the obliteration of dis-
section planes will obligate the brachial artery dissection
along with neurolysis. In this location it is rare for the
nerve
to branch,
but
on occasion
anomalous
motor
branches may go into the brachialis muscle and there may
be on occasion a sensory branch contribution
to the
medial antebrachial cutaneous nerve. It is rare for a high
median to ulnar communication (Martin-Gruber anasto-
mosis) but if encountered,
such connections should be
preserved. Furthermore, at this level the nerve must be
differentiated from the ulnar and the medial antebrachial
cutaneous with which it may be on occasion confused. The
medial antebrachial cutaneous nerve is smaller in caliber
and runs more medially. At times, due to intense scarring
and tissue distortion, dissection may have to be taken up
under the pectoralis major muscle to confirm the nerve
origins and allow precise identification. The ulnar nerve, in
contradistinction,
is usually
intermediate
in caliber
between the median nerve and the medial antebrachial
cutaneous nerve and will run obliquely in the arm to a
more medial position on the internal superior surface of
the triceps muscle.
Nerve stimulation of functioning elements may be help-
ful but because both nerves stimulate wrist and finger
flexion, distinguishing the two nerves on the basis of in-
complete stimulation with a disposable stimulator may on
occasion result in erroneous conclusions. The medial ante-
brachial cutaneous
is a pure sensory nerve, usually of
smaller caliber between 2 and 3 mm, and will have no
motor function. The nerve usually has no branches in this
location, but a nerve to the pronator teres may arise on
occasion up to 7 cm above the epicondyles. Distally the
lacertus fibrosis will be divided to expose the nerve.

936
Peripheral Nerve: Brachial Plexus
Figure 127-4
The cubital exposure of the median nerve shows prox-
imally the division of the lacertus fibrosis and the mobilization of the
pronator teres muscle and its nerve branches to expose the median
nerve. The anterior interosseous nerve arises at this level.
Cubital Exposure
The cubital exposure of the median nerve will start as the
continuation of the brachial exposure of the median nerve
References
1.
Hollinshead
w. The Back and Limbs. Anatomy
for Surgeons,
Vol 3.
New York: Harper and Row; 1969
2.
Sunderland
S. Nerve and Nerve Injuries.
Edinburgh:
Churchill;
1978
3.
Kline DG, Hudson
AR. Nerve Injuries:
Operative
Results
for Major
Injuries, Entrapments
and Tumors.
Philadelphia:
WB Saunders;
1995
in the arm. The medial groove between the brachialisand
the triceps can be palpated, usually in association witha
brachial artery pulse. Thiswill mark the proximal endofthe
incision. The incision will then be taken distally to thelevel
of the cubital flexion crease. At this level the incisioncon-
tinues medially in the flexion crease and then inferiorlyin
the middle of the forearm.
Thenerveisfoundinassociationwith the brachialartery
medial to the brachialis muscle. From this location it isdis-
sected distally dividing the lacertus fibrosis, a fibrous
aponeurosis arising from the biceps muscle, which overlies
the nerve in this location. Pronator teres branches should
be identified and preserved, They may arise severalcen-
timeters above the condyles to a couple of centimetersbe-
low them. The nerve can then be followed distally to the
point where it goes under cover of the pronator teres mus-
cle.Thismuscleinassociationwith the flexorcarpiradialis
and palmaris longus muscle may be dissected distallyand
retracted medially to allow for further exposure of the
nerve. This exposure can be taken to the point wherethe
nerve divides under the cover of the flexor digitorum su-
perficialis muscle.
Closure
In all exposures
the muscles are split and dissected
freefor
mobilization rather than divided. As a consequence, when
the median nerve has been exposed and operated
upon clo-
sure is quite simple, The Penrose drains that have beenused
to mobilize the nerve and its branches are removed,the
surgical field is irrigated with a saline solution, hemostasis
is achieved with bipolar electrocautery, the retractors are
removed, and the muscles are allowed to fall backintoposi-
tion. The subcutaneous tissue is reapproximated with2-0
resorbable suture, the subcuticular layer is reapproximated
with 3-0 resorbable suture, and the skin is closed with
Steri-Strips.
4.
Tiel RL.Other median nerve compression syndromes. In: KayeAH.
McL Black P, eds. Operative
Neurosurgery.
London: Churchill Living-
stone; 2000

128
Radialand Ulnar Nerves
R.Patrick Jacob and David A. Peace
. Indications
.
Surgical Technique
Incision and Dissection
. UlnarNerve
Incision and Dissection
Exposureof the radial and ulnar nerves in the upper extrem-
ityis a commonly used procedure for surgical exploration.
Theindications for this include trauma requiring decom-
pression or repair. release of entrapment neuropathies. and
removalof nerve sheath tumors. The key elements of expo-
sureof peripheral nerves include limiting injury to overlying
structures. allowing sufficient exposure of the anatomy in
question to allow repair, transposition. decompression or
tumor removal. and minimizing scarring or contractures
postoperatively.
.
Indications
. Trauma
.
Release of entrapped nerves
.
Nervesheath tumors
.
Surgical Technique
Incision and Dissection
Exposureof the radial nerve in the arm begins as the nerve
formsfrom the posterior cord of the brachial plexus.distal to
the axillary nerve. Lesions below the plexus are best visual-
ized from a posterior or posterolateral approach. The origin
and course of the radial nerve make exposure of the entire
length of the nerve very difficult with a single surgical ap-
proach.Atraditional anterior deltopectoral incision for the
lowerplexus will allow exposure of the takeoff of the radial
nerve from the posterior cord of the plexus. but more distal
exposure cannot be reasonably obtained via the technique.
The preferred approach for exposing the nerve is via a
posterior or posterolateral
incision in the upper arm
(Fig.128-tA). Usinga gently curved incision beginning -5 to
7cm below the acromion process. the subcutaneous tissues
and fasciaare incised, exposing the long and lateral heads of
the triceps (Fig.128-18).1 Caremust be taken to avoidinjury
to the posterior cutaneous nerve of the arm traveling in the
subcutaneous tissues. Asthese muscle bellies are separated,
the radial nerve is identified coming from under the teres
major. traveling just deep to the deep brachial artery. over
the medial head of the triceps muscle (Fig.128-1 C).Ifaddi-
tional length is needed for the exposure. the incision may
proceed in an extensile fashion with dissection carried proxi-
mal to the lateral head.2The first branch of the nerve arises in
the axilla.the posterior cutaneous nerve of the arm. and sup-
plies the dorsomedial skin of the upper arm. Branches to the
three heads come off starting -7 cm below the acromion
process. The branch to the long head exits first. followed
quicklyby branches to the medial then lateral heads.
The nerve then traverses the lateral intermuscular septum.
between the brachialis and brachioradialis muscles.Here the
nerve may lie directly on the humerus. At this point the nerve
is relatively tethered in the fasciaand it is here that compres-
sion or stretch injuries can occur. particularly with humeral
fractures.3Distalto this point branches to the brachialis mus-
cle leave the nerve and enter the lateral aspect of the muscle.
Approximately 3 cm above the lateral epicondyle. the nerve
givesup branches to the brachioradialisand extensor carpi ra-
dialis longus (Fig. 128-1D). As the nerve passes anterior to
the epicondyle. it divides into superficial and deep branches.
The nerve passes deep to the brachioradialis. The superficial
branch takes a more lateralcourse. passing under the brachio-
radialistendon and piercingthe fasciaon the dorsolateral sur-
face of the forearm. Thisis a common site of compression of
the superficialbranch ofthe nerve.4
The deep branch of the radial nerve enters the forearm
between the two layers of the supinator muscle in a contin-
uation of the radial tunnel. supplying that muscle. The
nerve is also crossed by the recurrent radial artery just prior
to entering the supinator muscle. which is a common site of
compression. The leading edge of the supinator muscle of-
ten has a tendinous component. the arcade of Frohse.which
can compress the traversing nerve. After exiting from under
937

B
c
Figure128-1
(A) The incision for expo-
sure of the upper radial nerve isdemon.
strated. The incision begins -5 cmbelow
the acromion process between the long
and lateral headsof the triceps muscle.It
extends toward the olecranon in agentle
curve. (8) The long head of the tricepsis
retracted allowing exposureof the nerve
asit exits from under the teres major.The
nerve is found to travel with the deep
brachial artery. Proximal exposureislim-
ited by the branches to the tricepsmus.
cle. Separation of the long and lateral
headsof the muscleallowsfor exposureof
the upper radial nerve. (C) Distallyinthe
arm, the nerve comes to lie betweenthe
brachioradialisandthe tricepsasit pierces
the intermuscular septum. The middle
and distal thirds of the arm arecommon
sitesfor radialnerveinjuries.
938
PeripheralNerve:BrachialPlexus
/----
--......
)'
-"'
,
////
/
",
;'
."
--
A

128
Radialand Ulnar Nerve
939
---. ...-
- ---~
-
,
--
D
E
the supinator, motor branches exit to the forearm and finger
extensors (Fig.128- tD).
.
UlnarNerve
Theulnar nerve arises as the terminal branch of the medial
cordofthe brachial plexus. It exits the axilladeep to the infe-
rior boarder of the pectoralis major muscle, traveling in the
planebetween the bicepsand triceps muscles.Approximately
Figure
128-1
(Continued)
(D) The
radial nerve divides into the posterior
intereosseous nerve and the superficial
sensory branch as it emerges from the
sulcus between the brachioradialis and
biceps muscles. The deep branch enters
the superficialfibersofthe supinatormus-
cle, exiting distally with branches to the
extensor
muscle
group.
(E)
Cross-
sectional anatomy ofthe proximalthird of
the forearm.
8 to 10cm above the medial epicondyle, it pierces the medial
intermuscular septum. There are no motor branches of the
ulnar nerve in the arm, although frequently the branch to
the flexor carpi ulnaris will leave the nerve and traverse the
cubital tunnel in the same adventitial sheath.s The nerve
passes from the arm into the forearm through the cubital
tunnel. In the proximal portion of the tunnel, the nerve is
covered by an arcade of tendinous fibers, which can be a
source of compression. Capsular branches of the nerve exit
at this level and innervate the elbow joint. The ulnar and

940
PeripheralNerve:BrachialPlexus
humeral heads of the flexorcarpi ulnaris form the roof of the
intermediate portion of the cubital tunnel and may thicken,
causing compression. Elbow flexion also causes effective
narrowing of the diameter of the tunnel raising pressure on
the ulnar nerve, which may also aggravate symptoms of cu-
bital tunnel syndrome. The leading edge of the two heads of
the flexorcarpi ulnaris may bejoined be a thickened band of
issue.Osborne's band, which is a common site of nerve com-
pression. The final segment of the tunnel consists of the two
flexor carpi ulnaris muscle bellies and connective tissue.
Branches to these heads exit the nerve usually in the second
portion of the tunnel and enter the muscle a few centime-
ters distally,within the third portion of the tunnel.
The nerve traverses the forearm between the flexor carpi
ulnaris and the flexordigitorum profundus, to which branches
are given,usually supplyingflexionto the fourth and fifthfin-
gers. Halfway down the forearm, the nerve runs along with
the ulnar artery. Twosensory branches, the palmar and dorsal
cutaneous branches.exit the nerve in the distal forearm.
The nerve enters the hand through the ulnar tunnelor
Guyon's canal. The nerve travels just medial to the ulnar
artery as it passesunder the palmarcarpalligament.Aline
drawn from the medial epicondyle to the lateral aspectof
the pisiform eminence would nearly trace the courseofthe
nerve. In the ulnar tunnel the pisiohamate ligamentandthe
pisiometacarpalligament
are common sources ofcompres-
sion. Asthe nerve passes through the tunnel it dividesinto
a superficial sensory branch and a deep motor branch.The
deep motor branch passes around the hook of the hamate.
and then innervates the ulnar hand intrinsic muscles.6
Incision and Dissection
Surgical exposure of the ulnar nerve for cubital tunnelsyn-
drome begins with defining the intermuscular compart-
ment between the biceps and triceps. Oncethis islocated.a
sigmoid incision is made 8 to 10 em proximal and distalto
the cubital tunnel (Fig. 128-2A). During the subcutaneous
A
--
8
Figure 128-2
(A)Incisionforexposureofthe ulnarnerveinthe arm. Theincisionmaybe extended proximallyto expose the nerveas itarisesfrom
the medial cord of the brachial plexus in the axilla. The demonstrated
incision allows for adequate exposure of the nerve for simple decompressionof
the ulnar nerve, as well as anterior transposition.
(8) During subcutaneous
dissection, the medial antebrachial cutaneous
nerve should be identified
and spared. The nerve is identified in the intermuscular septum between the biceps and triceps and traced distally.