Ultrasound-Guided Chemodenervation Procedures

12. INSTRUMENTATION AND KNOBOLOGY
91
sequence or movie. The screen can be frozen and a single image saved or a cine/
video sequence can be saved. Intensity (amplitude) of echoes is converted to gray-
scale images where brightness is proportionate to returning echo strength (Figures
12.9 and 12.10) (13,22,23).
M-Mode/Motion Mode
US image is displayed as a continuous display on the horizontal axis of the monitor. It is
used primarily in cardiology to track cardiac and valve motion and also used in MSK/
Neuro research to track contraction or shortening velocity of a muscle (Figure 12.11)
(13,22,23).
Doppler Imaging
The Doppler effect is covered elsewhere in this text. In brief, Doppler modes detect
motion under the transducer, in clinical practice this represents fl ow in a vessel. There
are various Doppler modes used in clinical practice including color, power, and pulse
wave (spectral). In color Doppler mode, movement is displayed as a color, which can
discriminate between fl ow in a vessel versus a nonvascular structure, which may, at
times, take on the appearance of a vessel (nerve, tendon, cyst) (Figure 12.12) (23,24).
Color Doppler is useful for a wide variety of procedures including chemodenerva-
tion. When used during procedural guidance, color Doppler allows a physician to
identify the target structure, as well as any vessels in the area and redirect the needle
away from these vessels. Spectral/pulsed wave Doppler displays the fl ow rate and
has been used in studies evaluating the effect of chemodenervation of muscles/ves-
sel fl ow (25).
Figure 12.9 B-mode US image, linear
transducer posterior calf.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
92
Figure 12.10 B-mode US image, cur-
vilinear transducer, gluteal region.
Figure 12.11 M-mode ultrasound image.
3D/4D Modes
3D/4D modes are widely used in clinical practice but have limited applications for pro-
cedural guidance including for chemodenervation procedures.

12. INSTRUMENTATION AND KNOBOLOGY
93
SCANNING/PROCEDURAL SUPPLIES
US Supplies
A coupling agent is required to reduce skin impedance and enhance sound transmission
through the skin to deeper structures. While saline can be used, most sonographers use
a viscous water-based gel. This gel can be purchased in conveniently sized squeeze bot-
tles/containers, which are stored on the machine. It is more cost effective to refi ll these
smaller bottles from a larger container. Sterile transducer covers and sterile gel pack-
ets can also be purchased (Figure 12.13). Clinical practice varies with some clinicians
routinely using a sterile sheath/gel for all invasive procedures while others do so only
for specifi c procedures or in special circumstances (4,13,26). Sterile supplies and sterile
techniques are universally recommended for joint injections. Sterile transducer covers
should be used during procedure or for diagnostic imaging if the patient has an open
skin lesion, active infection, or known to be colonized with bacteria such as methicillin-
resistant staphylococcus aureus (MRSA). Currently there is no standard practice or evi-
dence that requires the use of sterile gel during US procedural guidance (25,26). Many, if
not most, practitioners performing US-guided chemodenervation procedures do not use
sterile gel. The skin is cleansed as per standard preprocedural (injection) techniques. After
the gel is applied and the area scanned, the gel can be wiped away from the site where
the needle will enter the skin if desired. In over 8 years of US scanning at a large research
center and in clinical practice, we have encountered no infections using this technique
Figure 12.12 Color Doppler ultrasound image, posterior calf transverse.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
94
for BoNT chemodenervation. The authors routinely use a sterile sheath and gel for joint
injections, deposteroid injections and frequently for nerve blocks.
Transducer Cleaner
Transducers should be cleaned per the manufacturer recommendations. Most manu-
facturers recommend nonalcohol-based wipes/transducer cleaners. The transducers
should be carefully cleaned after every use removing excess gel. Towels or tissues and
skin wipes are needed to remove excess gel from the patient’s skin when scanning is
completed (25,26).
Stand-Off Pads
Stand-off pads are sometimes required for scanning superfi cial structures (Figure 12.14).
These pads are made out of an acoustically transparent solid/gel like material that
functions to increase the distance between the surface of the skin and the transducer.
This enhances imaging of very superfi cial structures that have little overlying sub-
cutaneous fat, that is, skin, hand, face. These very superfi cial structures may be dif-
fi cult to image on US because there is not enough distance between the target and
the transducer for adequate beam focusing. In lieu of a stand-off pad, gel can be
mounded up on the surface of the skin and the transducer “fl oated” on the mound of
gel (Figure 12.15). Another option is to fi ll the fi nger of a glove with gel and use this
as a “stand-off pad.”
Procedural Supplies
Syringes, needles alcohol wipes. Needles for injection can vary from 30g 0.5 to 1 inch
needles, which are used for superfi cial structures (salivary glands/superfi cial muscles)
Figure 12.13 (a) Sterile transducer cover/gel/Supplies. (b) Sterile transducer cover deployed.

12. INSTRUMENTATION AND KNOBOLOGY
95
to 25g 2 to 3 inch needles required for deeper muscles such as the piriformis, or in obese
patients. A preliminary or scout scan of the region should be performed to confi rm
the depth of the target structure. This allows physicians to choose a needle of the cor-
rect length/gauge. Accurate assessment of target depth is one of the clear advantages
of US over other localization techniques for chemodenervation. Clinicians should be
aware that if a tangential rather than direct approach to the target is required, this will
increased the length of needle required to reach the target.
ULTRASOUND MACHINE OPERATION AND KNOBOLOGY
US scanning is highly operator dependent. It is imperative that clinicians be familiar
with US equipment presets, other controls, and the potential pitfalls encountered dur-
ing scanning. Although modern US systems come with a variety of preset programs that
speed the startup and imaging, there are a number of controls that must be adjusted by
the operator.
Figure 12.14 Stand-off pads.


Figure 12.15 Gel “stand-off pad.”

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
96
Set Up
Patient Information
Prior to scanning, the patient’s identifying information must be entered or typed into
the system to create a data fi le and to save images. This fi le allows this data to be recalled
and reviewed off-line (Figure 12.16).
Presets
Most machines have a variety of preset programs for imaging different body systems
(Figure 12.17). These presets facilitate transducer selection, provide fi lter/machine settings
and signal processing to enhance images of specifi c body systems. For chemodenervation
procedures, a MSK preset should be used. When performing chemodenervation of the sal-
ivary glands using a thyroid or breast preset may provide better image quality (12,13).
Annotation
This control option allows the image/screen to be labeled, that is, target name and so on.
Clinicians should label the muscle or target for documentation purposes and for later
review by themselves or by unfamiliar clinicians. Examples include labeling the screen;
fl exor forearm, transverse view, injection FCR (fl exor carpi radialis) or transverse view,
posterior calf, injection medial gastrocnemius. Many machines have muscle or target
lists, which can be added to or modifi ed speeding up the annotation/labeling process.
Figure 12.16 Patient data entry screen.

12. INSTRUMENTATION AND KNOBOLOGY
97
TRANSDUCERS: SELECTION/HANDLING
Transducer Selection
Clinicians must match the transducer frequency, size, and shape to the intended use
(Figure 12.4). Absent the right transducer, a $300,000 machine will not provide adequate
images for diagnostic or US-guided procedures. MSK imaging, including most chemod-
enervation procedures, requires linear or curvilinear transducers of the correct size and
frequency (13,14,21).
In linear array transducers, the piezoelectric crystals are arranged side by side on the
transducer and produce a rectangular image (Figure 12.9). This has the advantage of the
all sound-beam echoes traveling in a similar direction, reducing anisotropy. In curved
linear or curvilinear transducers, the crystals are arrayed side by side, but in a curved,
not fl at, array. This curved array provides a wedge shaped image, which enhances
depth penetration (Figure 12.10). Curvilinear transducers are generally of lower fre-
quency than linear transducers. The lower frequency and the divergence of the US beam
created by the geometry of the transducer lead to lower image resolution and increase
the risk of encountering anisotropy (see the Glossary and US basic physics and proper-
ties of tissues chapters). A hockey stick transducer is a small foot-print linear transducer
useful for scanning irregular body surfaces, intrinsic muscles of the foot/hand/face, or
pediatric patients (4,12–14,21,22).
Transducer Frequency
For most scanning in the upper limb or calf, a linear transducer in the range of 5 to 12
MHz is suffi cient. Higher frequency transducers (up to 18 MHz) are used when scan-
ning or injecting superfi cial structures such as intrinsic muscles of the foot and hand,
oromandibular or facial muscles, and salivary glands. The ultra-high frequency of these
transducers is useful for image clarity. Curvilinear transducers with lower frequencies
(2–5MHz) are often required for deep muscles of the pelvis, hip or in obese or very mus-
cular patients (4,12–14,21,22).
(b)
(a)

Figure 12.17 (a) Machine preset/set up, Phillips IU 22 (b) Machine preset/exam selection Terason 3200.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
98
Extended Field of View
A feature available on some high end machines in which the computer generates a sin-
gle reconstructed image after the transducer is moved along the length of the region of
interest, limb or other structure (Figure 12.18) (21).
Specialty Transducers
Endocavity transducers are designed to be inserted into body cavities such as the esoph-
agus, vagina, or rectum (Figure 12.19). These transducers are required for US-guided
BoNT procedures of the esophageal sphincter, other GI (Gastrointestinal) indications,
bladder wall injections, vaginismus, or benign prostatic hypertrophy. 3D and 4D trans-
ducers are also available. 3D imaging technology varies but requires position sensing
and tracking to display an image with either surface rendering or multiplanar render-
ing (MPR). 3D transducers are primarily used for OB/GYN applications to visualize
the fetus. 4D imaging uses a specialized transducer that displays real-time motion of
3D images. 3D transducers have limited application for chemodenervation procedures
but are useful in tracking post injection muscle changes including muscle size, length,
or contraction velocity (Figure 12.13) (21,22).
Holding the Transducer
Because the transducer/gel/skin interface is slick, the transducer is prone to slipping
on the skin surface. Novice clinicians frequently fail to maintain a proper grip/hold on
the transducer (13,14,21). This allows the transducer to slide or move during imaging
which may result in losing the view of the target and/or the needle. The transducer
should be held between the thumb and index or thumb and index/middle fi ngers. This
(a)
(b)

Figure 12.18 Extended fi eld of view images (a) Vastus medialis, Phillips IU 22 (b) Achilles tendon
Terason 3200.

12. INSTRUMENTATION AND KNOBOLOGY
99
allows the fourth and fi fth digits to rest on the patient, stabilizing the transducer posi-
tion (Figure 12.20) (13,16).
Transducer Orientation
All transducers have a mark or notch on one end. The notch or mark always cor-
responds to left of the display screen (Figure 12.21) (14,27,28). The unmarked side of
the transducer corresponds to the right side of the display screen (Figure 12.21c). The
(a)
(b)
Figure 12.19 (a) Transesophageal transducers (b) Transvaginal/rectal transducer.
(a)
(b)

Figure 12.20 Holding the transducer (a) correctly holding/stabilizing the transducer by maintaining
hand in contact with patient (b) incorrectly holding transducer, which is not stabilized.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
100
sonographer must correctly orient the transducer during imaging. There are at least
two imaging orientation conventions used in clinical practice, which leads to varia-
tions in how the transducer is positioned and hence how structures are displayed.
Two of these conventions include Standard Cross Sectional Imaging Protocol and
Simplifi ed Imaging Protocol:
SCIP—When using the Standard Cross Sectional Imaging Protocol (SCSIP) the goal
is to produce ultrasound images that mirror those of other cross sectional imaging
applications, such as CT and MRI. With CT and MRI, structures are displayed on the
screen with the right side of a patient oriented on the left side of monitor/image. The
SCIP is used by many clinicians because it mimics what an examiner sees when facing/
examining a patient, i.e., the patient’s right side is to the examiner’s left side. During US
imaging using the SCIP and scanning in the transverse/axial or coronal/frontal plane,
structures on the patients right are therefore displayed on the left side of the monitor.
When scanning in the sagittal/longitudinal plane the transducer is oriented to display
proximal/cephalad structures to the left, and distal/caudal structures to the right. As
noted above, manufacturers place a notch or mark on one side of the transducer. This
mark/notch corresponds, by convention, to the left side of the ultrasound display. Thus,
when using the SCSIP, place the notch or mark on the transducer toward the patient’s
right side for transverse/axial and coronal images. Orient the transducer mark/notch
toward the patient’s head for sagittal/longitudinal plane images. SIP—When using the
Simplifi ed Imaging Protocol (SIP) and scanning in transverse/axial or coronal/frontal
plane, the mark/notch on the transducer is oriented medially on a patient. Therefore
medial structures are displayed on left of the display screen and lateral structures are
displayed on the right.
In longitudinal/sagittal scans, using the SIP the notch/mark of the transducer is ori-
entated proximal/cephalad as it is with the SCIP. Therefore proximal or cephalad struc-
tures are displayed to the left and caudal or distal structures to the right in both the SIP
and SCIP conventions. If the transducer is oriented incorrectly, most machines allow the
operator to invert the image to the correct orientation (14). Using a consistent transducer
orientation is particularly important for novices to US scanning. It minimizes confusion
when viewing structures and learning the pattern recognition required in US.
(a)

(b)
(c)
Figure 12.21 Transducer orientation mark/label; (a) and (c) correspond to left of display screen.
Unmarked side of transducer corresponds to right side of display screen.

12. INSTRUMENTATION AND KNOBOLOGY
101
Moving/Scanning with the Transducer
As noted above, the beam is narrow and only creates an image through a thin slice of
the body or a structure. To compensate for this, the operator must reposition or slide
the transducer along the skin to view the length and width of a structure in its entirety
(13,14,28). Chemodenervation procedures require a scout scan of the entire muscle or
structure. This allows a clinician to judge the depth of the target and select the best site
for injection. This scan also detects vessels, nerves, or other structures to be avoided
during needle insertion. Real-time imaging allows the physician to determine the most
direct route to the muscle/target and observe the injectate entering the target. When
complex overlapping muscles are the target for injection, a preliminary US scan may
reveal a site where multiple muscles can be targeted with a single skin penetration or
needle stick. As patients, particularly children, prefer as few needle sticks as possi-
ble, this technique is another advantage of US during chemodenervation procedures
(12,20,28–30).
The transducer is also rotated, rocked, or moved along its short and long axes in
maneuvers referred to as “toggling,” “rocking” (short axis), or “heel-toe-ing” (long axis).
These maneuvers are used to angle the US beam, reduce anisotropy, acoustic shadow-
ing, and to enhance imaging of a target or needle (13).
CONTROLS OPERATED BY THE CLINICIAN
Depth Control
The depth control adjusts the screen display to a maximum or minimum depth for a
specifi c transducer. Adjusting this control allows the operator to maximize the view
of the region of interest without viewing deeper structures, which are not of interest.
This provides the maximum view of superfi cial structures and improves frame rate.
Because frequency of the US waveform determines depth of penetration, selecting the
correct transducer determines depth achieved when scanning. Adjusting the depth
control will not compensate for the wrong transducer, that is, one with a frequency
too high to reach the depth of penetration needed to scan deep structures (Figures
12.22–12.24).
(b)
(a)
)

Figure 12.22 Controls (a) Phillips IU 22 controls (b) Terason controls.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
102
(b)
(a)

Figure 12.23 Manual controls Phillips, IU 22.
Figure 12.24 Terason manual controls.
Gain Control
Gain control adjusts degree of echo amplifi cation and thereby the overall brightness
of an image. The overall gain control amplifi es equally all the echoes returning to the
transducer and processed by the machine (Figures 12.22–12.24). Too much gain results
in an overly bright image that is “whited out” or hyperechoic. Too little gain and the
image will appear too dark or hypoechoic. Adjust the overall gain to optimize the signal
intensity in the region of interest.
Time Gain Compensation (Depth Gain Compensation)
Depth gain compensation (DGC) also referred to as time gain compensation (TGC) is
adjusted to compensate for attenuation of the US beam and is measured in decibels, dB.
This attenuation occurs as the acoustic energy in the beam is lost passing through super-
fi cial tissues and is absorbed/dissipated as heat. Higher frequency sound is absorbed
more than low frequency sound, which accounts for the depth limits of high frequency
transducers. Use the DGC/TGC slide controls (slide pots) to adjust the brightness of

12. INSTRUMENTATION AND KNOBOLOGY
103
structures at various depths on the displayed image. Slide the TGC/DGC controls left
or right to decrease or increase the gain/brightness, respectively, in the region of interest
to optimize the image (Figures 12.22–12.24) (13,22,31).
Focal Zone(s)
When transmitted to the body, the US beam created by the transducer initially narrows to
a minimum width and then widens as it travels further through the body. The beam, at
its narrowest point, is referred to as the Focal Zone. This narrow zone represents the area
of highest spatial/lateral resolution. The focal zone or zones may be selected and set by
the operator. Focal zones should be adjusted to encompass the region or regions of inter-
est when scanning. Using multiple focal zones degrades frame rate and reduces tempo-
ral resolution of real-time B mode scanning (Figures 12.25 and 12.26) (13,22,31,32).
Frame Rate
As noted above frame rate is important for temporal resolution. Frame rates > 20 frames/
sec improve imaging of rapidly occurring events including insertion of a needle. Depth
of scanning and the number of focal zones both reduce the frame rate and thereby, tem-
poral resolution (This is because each focal zone requires a separate US beam). To main-
tain a higher frame rate, use the minimum number of focal zones required for imaging.
The focal zone or zones are displayed as a caret or mark on the image display (usually
the right side) (Figures 12.25 and 12.26). Use the focal zone control to move the focal
zone to the region of interest (13,22).
Transmit or Acoustic Power
Transmit or acoustic power adjusts the amount of energy transmitted by the transducer
to the patient. This should be kept at the lowest level needed to create acceptable image
quality.
(a)
(b)
Figure 12.25 Focal zone Phillips IU 22 (a) superfi cial abductor digiti minimi (b) quadriceps.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
104
Capturing/Storing Images/Cine-clips
When performing either diagnostic or US-guided procedures, there must be some record
of the procedure. This requires storing, saving, and or printing images and or video clips
collected during the procedure. Note: If you do not store/save/collect an image in essence,
you did not perform the procedure and hence cannot bill for the procedure. Images can
be saved either as a still photo/image or as dynamic cine-clip/videos. Images are col-
lected/stored on most machines by clicking or selecting the appropriate icon/button or
other control on the machine. The computer then stores the images/videos, which can be
reviewed off-line and then downloaded as desired. A useful feature of some machines is
the capability to download images directly to the hospital/clinic picture archiving and
communications system (PACS) via a wireless connection. Be aware that images/videos
may be collected in various fi le formats including DICOM images, JPEG, MPG, WMV,
and so on. Reviewing DICOM fi les off-line of the US machine requires software (DICOM
reader) installed on a computer. DICOM readers can be purchased or obtained by a free
download. Free downloads may allow limited image manipulation but this is often ade-
quate for clinicians performing chemodenervation procedures.
Freeze Frame
This control allows the image on the screen to be frozen and reviewed during
scanning.
Beam Steering
The US beam is electronically directed right or left during imaging. Steering enhances
needle visualization and may reduce anisotropy. Beam steering can also enhance needle
visualization by increasing refl ection of the US beam.


(a)
(b)
Figure 12.26 (a) Focal zone, Terason set superfi cial for wrist hand. (b) Focal Zone, Terason, set deep
for lateral hip.

12. INSTRUMENTATION AND KNOBOLOGY
105
Needle or Biopsy Guide
This control is used in combination with a needle guide attached to the transducer.
When activated, a line representing the needle path in relation to the transducer appears
on the display screen. The operator can orient the line over the target structure. This
may help clinicians direct the needle to the intended target but is of limited use for
chemodenervation or for experienced clinicians.
Dual Image
Selecting dual image activates a split screen which allows side to side comparison of
normal/abnormal sides or before/after injection or procedures.
Body Markers
Places a drawing of a body area on the screen (abdomen, pelvis, limb etc.).
Measurement Tools
Trace: Allows the operator to manually outline an area to be measured. Ellipse: The
computer generates a circle or ellipse that can be adjusted to size to outline a structure.
Other measurement tools allow accurate measurement of circumference, width, and
length of structures.
EDUCATION AND TRAINING
Although US imaging remains highly technical, technological advances facilitate use
of equipment allowing the instrumentation to be easily mastered by a motivated, self-
directed clinician. Despite these advances, the learning curve remains steep when
adding US-guided procedures to clinical practice. This steep learning curve and the
need to learn a new skill may be intimidating for physicians who are unfamiliar with
sonography.
There are a number of postgraduate training options including self-directed on-
line educational websites (33–36), Table 12.2, Medical Society/Academy and Industry
sponsored didactic, and hands-on workshops. These courses provide a variety of edu-
cational opportunities for interested physicians. Although many of these are MSK-
specifi c courses, there is signifi cant overlap for physicians interested in US primarily
for chemodenervation procedures. In the past 2 years, courses specifi c to US-guided
chemodenervation have become available providing additional opportunities for
training.
No course is a substitute for hands-on experience and regular practice. This is required
to master the instrument as well as scanning and procedural techniques. The benefi ts to
physicians and patients make this effort worthwhile.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
106
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American Institute for Ultrasound in Medicine (AIUM):
European League Against Rheumatism (EULAR):
European Society of Skeletal Radiology (ESSR):
Munich Ultrasound Course:
University of Michigan Ultrasound:

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Trunk
Katharine E. Alter, Michael C. Munin, and Steven M. Skurow
This chapter covers basic transducer handling and scanning tips/techniques that are
required for clinicians to incorporate ultrasound (US)-guided chemodenervation proce-
dures into their clinical practice.
LOCALIZATION TECHNIQUES AND GUIDANCE FOR
CHEMODENERVATION PROCEDURES
To perform chemodenervation procedures (botulinum toxin [BoNT] injections, nerve/motor
point blocks), clinicians must have a thorough knowledge of anatomy including: anatomical
planes, cross sectional and functional anatomy. No localization technique, including sophis-
ticated imaging guidance techniques such as US replaces this fundamental requirement.
Conventional localization techniques for BoNT injections and nerve blocks include: the
use of anatomic reference guides, palpation, PROM/AROM, electromyography (EMG),
and electrical stimulation (E-Stim). Until recently, imaging-based guidance techniques
have been used less frequently. In recent years advances in US have lead to its increased
use for a variety of musculoskeletal (MSK) and chemodenervation procedures, both
as an add-on to conventional guidance methods or as a stand-alone technique (1–13).
When used by experienced clinicians, US increases the accuracy of targeting, speed of
target localization, reduces potential risk to patients, and improves patient comfort dur-
ing MSK, chemodenervation, and other procedures (2–7,9). To successfully include US
guidance to their practice requires that clinicians understand the basics of US physics/
image acquisition and a working knowledge of and profi ciency in equipment operation.
US scanning/procedural guidance also requires physicians learn a new set of motor
skills including the correct handling, orientation, and manipulation of the transducer
during imaging, needle/syringe manipulation during procedures (11,12).
ADVANTAGES AND DISADVANTACES OF US FOR
PROCEDURAL GUIDANCE
US is used extensively by a number of medical/surgical specialties for diagnostic imaging
and to provide procedural guidance for a variety of procedures including chemodenerva-
tion procedures (nerve blocks, BoNT chemodenervation). US has a number of advantages
over other image-guided procedure techniques, but it also has limitations (Table 13.1).
Advantages of US guidance include its lower cost and the portability of US compared
13
Ultrasound for Procedural Guidance:
Scanning—Techniques and Tips

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
109
to other imaging systems such as fl uoroscopy or computed tomography (CT), which are
tied to the radiology suite. Perhaps the most important advantage of US is the high resolu-
tion, exquisitely detailed pictures provided when imaging soft tissues and neurovascular
structures. The images obtained with high frequency US rivals or exceeds images pro-
vided by MRI. US provides a real-time, continuous view of the needle and target. With
US guidance, the needle’s path can be traced or tracked to the desired location and the
injection observed, throughout the procedure. The lack of ionizing radiation and dynamic
nature of US imaging are also advantages. Limitations of US include a clinician’s lack of
access to or familiarity with the equipment, the steep learning curve to acquiring neces-
sary skills, limited access to training, and the added set up time (compared to blind proce-
dures). Limitations/disadvantages of US (technologically) include the small fi eld of view
(FOV) provided by the transducer, lack of bone penetration, limited resolution at depth,
and the fact that US is highly operator dependant.
THE SCANNING ENVIRONMENT
The examination or procedure room should be set up in advance of a procedure to
ensure that the required equipment is present, functioning, and all the necessary sup-
plies available. Procedural supplies should be set up within easy reach of the physician/
sonographer. Attention to ergonomics is important, to prevent examiner fatigue and
pain. US images are best visualized in a low light environment and the overhead light-
ing should be reduced or turned off. Task lighting can be provided by an x-ray view box,
exam lamp, or fl oor lamp. This will provide the right lighting balance that is required to
both see the patient and to visualize the US images on the display screen.
Table 13.1 Advantages and disadvantages of ultrasound
Advantages of Ultrasound
Disadvantages of Ultrasound
Portability
Operator dependent
Relative cost compared to other imaging guidance
techniques
Limited access to training/education
- Lack of certifi cation
Real-time imaging with direct
- View of target
- View of needle
- Injectate
Equipment
- Limited access to equipment
- Technology/quality differences of machines
- All machines have unique set up/controls
No ionizing radiation
Lack of bone/joint penetration
No known contraindication
Limited fi eld of view/depth of penetration
High resolution of soft tissues including
- Muscles, nerves, blood vessels
- Cysts, masses
- Foreign bodies
Limited resolution with low frequency transducer
- Obese patients
- Deep Muscles
Increased accuracy compared to blind injections
Operator may require assistance

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
110
An electric high-low table (Figure 13.1) is strongly recommended to accommodate
transfers of patients with mobility challenges, facilitate positioning, and to adjust the
table height as needed during the procedure. A comfortable chair to allow a patient to
sit during procedures and a wheeled exam stool for the physician are also useful.
Patients should be comfortably positioned sitting, supine or prone depending on the
demands of the procedure. Anxiety, pain, or a cool room may increase the patient’s
dystonia or spasticity, which will negatively affect positioning and targeting during
chemodenervation procedures. Having a family member or caregiver present may
reduce the patient’s anxiety and facilitate positioning/transfers. In pediatric patients,
when the procedure is performed without sedation, a parent should be present. We
routinely include Child-Life-Therapists to provide procedural support and distraction,
which often signifi cantly reduces the child’s anxiety.
PATIENT/PHYSICIAN PREPARTION/POSITIONING
Due to the copious amounts of gel required during scanning, patients should change
into an examination gown or disposable scrubs. An alternative is to have the patient
wear a washable sleeveless top and shorts. Since it is inevitable that gel will get on the
patient’s (and the physician’s) clothing during a procedure, a gown or scrubs is perhaps
the better option. US transmission gel is water soluble and easily washes out of clothing,
but may stain delicate dry-cleanable fabrics. After scanning, the gel residue left on the
skin should be removed with a damp cloth or tissues.
POSITIONING THE MACHINE/SCREEN
As noted above, attention to ergonomics is important. Correct placement of the machine,
supplies, and the patient will reduce fatigue, pain, and eye strain in physicians who
may perform multiple procedures throughout the day. The physician should stand or sit
(a)
(b)
Figure 13.1 High–low examination tables.

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
111
in a position within easy reach of both the patient and the machine. The machine must
be positioned to provide access to the controls and provide a clear view of the display
screen (11). Physicians should consider positioning the machine to allow the patient to
view the US images/screen as most patients are interested in and distracted by viewing
the US images (1).
US PROPERTIES OF TISSUES
The reader is referred to the chapter on “Ultrasound Properties of Tissues” in this vol-
ume for a detailed discussion of this topic.
US SCANNING: ACQUIRING AND PRACTICING SCANNING SKILLS
To utilize US for procedural guidance requires both manual dexterity as well as some
technical skill. The clinician must simultaneously coordinate several tasks including
operation of the machine controls, manipulation of the transducer to optimize target/
needle visualization, and insertion of a needle. Coordinating these skills requires hands
on practice prior to applying this technique in the patient care arena. It is recommended
that clinicians practice guiding the needle using an imaging tool such as an injection/
procedure phantom such as the “Blue Phantom,” or others. Phantoms are blocks com-
posed of a sonolucent gel like material in which are imbedded targets that simulate
vessels or other structures (Figure 13.2). If a phantom is not available, an alternative is
a turkey breast into which are inserted several green or black olives. The echotexture
of the olives is distinct from the surrounding muscle of the turkey breast and serve as
target, which the clinician can aim toward. When using this technique, for infection con-
trol purposes, a transducer cover should always be used and the examiner should wear
gloves and use caution when inserting the needle to prevent inadvertent needle sticks.
(a)
(b)
Figure 13.2 (a) Ultrasound training phantom (b) US image of phantom with vessel/target to practice
needle insertion.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
112
Planning the Procedure
As noted in prior chapters, the beam of sound produced by a transducer is narrow and
only creates a narrow image through the body/of a structure. To view a structure in its
entirety, the operator must move, slide, or reposition the transducer along the length
and width of a structure (12,14). A scan of the entire structure to be injected should be
performed prior to any US-guided procedure, including chemodenervation. This scan
provides the clinician not only with information about the depth of the target but also
the best approach to the target and site for the injection. (11,12). The preliminary scan
will reveal neurovascular structures tendons, cysts, or masses to be avoided during nee-
dle insertion or during injection.
Prior to performing a procedure, scout scans should also be performed in both the
horizontal and longitudinal plane of the structure. This scout scan will provide informa-
tion about the depth of the target allowing the clinician to choose the correct needle to
reach the target. Clinicians should be aware that when referring to imaging plane and
body plane, the orientation of these two planes may not correspond for some targets
or muscles. For example, for the fl exor digitorum superfi cialis muscle, the anatomic
longitudinal and transverse plane of the muscle corresponds to the longitudinal and
transverse body planes (Figure 13.3 c,d). However, for the pronator quadratus mus-
cle, the long axis view of the muscle corresponds to the transverse plane of the body
(Figure 13.3 e,f). This is important when describing a procedure.
B-mode US provides real-time imaging and allows the clinician to track the needle to the
intended target and observe the toxin or other injectate. During US-guided nerve blocks,
US facilitates positioning the needle in a near nerve location, reduces the number of needle
passes, minimizes the need for E-Stim and the success rate for the procedure, and reduces
risk (14–17). When complex overlapping muscles are the target for injection, a preliminary
US scans may reveal a site for needle insertion where multiple muscles can be targeted
with a single stick. As patients, particularly children, prefer as few needle sticks as possible
this technique is another advantage of US during chemodenervation procedures (1,8).
Transducer Selection and Handling
Transducers are delicate and expensive and should be handled with care. Dropping the
transducer may damage the electronics.
Because the frequency of sound determines the depth of penetration and resolution,
transducer selection is critical. The higher the frequency of the transducer, the better the
resolution but high frequency is at the cost of depth penetration. Clinicians must choose
a transducer with a frequency range, which provides adequate depth of penetration to
view the target in its entirety. For deep structures, a curvilinear probe may be required.
For irregular, small surfaces, a hockey stick transducer may reduce the air-gap artifact,
which compromises sound transmission.
Because US scanning requires continual adjustment of the transducer position/orienta-
tion, it is critical that the clinician maintains control of the transducer at all times. Novice cli-
nicians often fail to maintain a proper grip/hold on the transducer. When not held securely,
the transducer will slip or slide on the slick transducer gel/skin interface. This will result in
the transducer sliding out of position and the view of a structure or needle will be lost.
To maintain a secure hold, the transducer should be comfortably held between the
thumb and index or thumb, index, and middle fi ngers, leaving the fourth and fi fth digits

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
113
(a)
(b)
(c)
(d)
(e)
(f)
Figure 13.3 Anatomic planes: (a) frontal/sagittal/coronal, (b) transverse/horizontal, (c) body and
muscle planes are equivalent longitudinal view FDS = long axis body orientation, (d) transverse view of
FDS = transverse body plane, (e) scan/injection: pronator quadratus where muscle/body planes do not
equate longitudinal axis of muscle = transverse body plane, and (f) transverse view of muscle = longitu-
dinal body plane.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
114
free to stabilize the transducer by resting on the patient. Maintaining contact between
the patient and the examiner’s hand stabilizes the transducer and will prevent it from
slipping (Figure 13.4 a,b) (11,13).
Transducer Orientation
US imaging is operator dependent. It is up to the clinician to correctly orient the trans-
ducer on the patient during scanning. The transducer should be placed on the patient
and oriented to provide the best view of the target, that is, either in the transverse or
longitudinal plane for chemodenervation procedures.
All transducers have a notch or mark on one end (Figure 13.5). This mark corresponds
to the left side of the monitor/display screen (Figure 13.6). The unmarked side of the
transducer corresponds to the right side of the display screen (Figure 13.7) (13). When
(a)
(b)
Figure 13.4 (a) Incorrect grip/hold on transducer; (b) correct grip/hold of transducer, stabilizing the
examiners hand on the patient.
Figure 13.5 Marked side of
transducers corresponding to
left side of display screen.

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
115
scanning in the longitudinal/sagittal/frontal planes (Figure 13.3a), the transducer
should be placed so that the left side of the display screen corresponds to proximal on
the patient (i.e., transducer mark oriented proximal). A detailed discussion of trans-
ducer orientation conventions is included in the Instrumentation Chapter of this text.
When scanning in the transverse/axial or frontal/coronal plane the transducer the
clinician with chose to image/scan using either the Standard Cross Sectional Imaging
Protocol (SCIP) or the Simplifi ed Imaging Protocol (SIP). These conventions are dis-
cussed in detail in the chapter on Instrumentation in this text. When the SCIP conven-
tion is chosen the transducer is oriented so that right of a patient is oriented to the left
side of the display screen. With the SIP convention the transducer is positioned so that
medial structures are oriented to the left of the display monitor.
(a)
(b)
Figure 13.6 US display screen (a) Phillips IU22 (b) Terason T3000.
Figure 13.7 Unmarked side of transducer corresponding to
right side of display screen.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
116
These varied conventions may confuse a novice clinician who is unfamiliar with the
screen display and pattern of US images. Inexperienced clinicians should ask what con-
vention is used at their practice/institution or pick one convention and stick with this
when scanning. This will minimize confusion when scanning and performing proce-
dure. It will also help the clinician learn the pattern recognition required for viewing US
images. Less experienced clinicians should check the transducer orientation each and
every time it is placed on the patient to ensure the correct/expected orientation. Once
familiar with US pattern recognition, clinicians will recognize when the image is inverted
because of transducer reversal and will automatically correct the transducer orientation.
If an image is inadvertently collected in the wrong orientation, most machines have a
feature that allows an image to be inverted.
Techniques for Scanning With or Moving the Transducer
As noted previously, the thin beam produced by the US transducer images only a nar-
row slice of the body. To optimize imaging it is necessary to move the transducer and
steer the thin US beam to visualize the entire structure of interest. The transducer is
rotated, rocked, toggled, or moved along its long and short axes to direct the US beam
and optimize imaging. Movements along the short axis are referred to as “toggling” or
rocking. Tilting the transducer on its long axis is referred to as “heel-toe” maneuvers
(11–13,18). These maneuvers are also used to reduce anisotropy, acoustic shadowing and
to enhance imaging of the target structure and the needle during procedures.
Transducer/Needle Orientation: Procedural Techniques and Tips
During chemodenervation procedures, the needle should be inserted under direct US
visualization, using real-time imaging. Other techniques described for procedural guid-
ance including an indirect or paperclip approach are not advised for chemodenervation,
particularly nerve blocks (11,18).
During real-time US-guided procedures, the needle must be inserted and the tip
maintained within the narrow US beam otherwise visualization is lost. When the view
of the needle tip is lost, it should not be advanced. The transducer should be moved
or repositioned until the needle tip is again identifi ed. If necessary, a small amount of
saline can be injected, which will reveal the position of the needle and enhance the view
via hydro-dissection of the adjacent tissues (11,12).
The initial scout scan will provide information about the depth of the target and the
length of the needle required to reach this depth.
Needles can be inserted either along the length, that is, long axis of the transducer (“in-
plane”) (IP) or across/under the short axis of the transducer (“out of plane”) (OP). In an IP
view, the entire length of the needle may be visualized, including the needle tip (Figure 13.8).
This requires the proper orientation of the needle, relative to the transducer (see below).
With the OP approach, the needle is visualized only as a hyperechoic dot (Figure 13.9).
Each of these techniques has advantages and disadvantages as detailed below.
In-Plane Approach
The primary advantage of an IP approach is that the entire length of the needle, includ-
ing the tip is seen (Figure 13.8b). The IP view provides information about the path of

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
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(a)
(b)
Figure 13.8 (a) Long axis
“in-plane” position of needle
(b) corresponding view of
needle.
(a)
(b)
Figure 13.9 (a) Needle
orientation for out of plane
view (b) corresponding
US image of needle tip as
hyperechoic dot.
the needle to the target, as well as location of the needle tip, which ensures that it is at
the desired site.
When the IP approach is performed correctly, the needle appears as a thin hyper-
echoic line. A posterior reverberation artifact may also be seen (11,12,18). This image of
the needed is obtained because most of the sound-waves are refl ected back to the trans-
ducer (see Chapter “Basic Physics” for full explanation) (Figure 13.8b). To obtain this
image of the needle requires the needle be inserted and maintained at a precise angle,
that is, at 90° to the US beam. To maintain this relationship, the needle is inserted parallel

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
118
along the length of the transducer. For the needle to be visualized it must remain within
the thin beam created by the transducer. Remember, the needle is highly refl ective of
sound only when inserted at 90° relative to the US beam. At more oblique (angles < 90°)
the view of the needle is compromised or may not be visualized as hyperechoic because
less of the sound is being refl ected back to the transducer to be processed.
The diffi culty in maintaining the needle/transducer orientation is one of several dis-
advantages of the IP technique. When the needle is not inserted at the correct angle, a
less intensely hyperechoic image is obtained, which compromises localizing the posi-
tion of the needle particularly its tip (Figure 13.10). It is particularly diffi cult to maintain
the needle at a 90° angle to the US beam when targeting very superfi cial or very deep
structures. When using lower frequency transducers, visualization of the needle/needle
tip is also compromised.
Another limitation of the IP technique is that maintaining the above angle often requires
an oblique path of the needle to the target. To obtain the 90° angle of the needle to US
beam often requires it be inserted at some distance from the target. This may require that
the needle travel through other structures in its course to the intended target/injection site
as is demonstrated in Figure 13.8b. In this transverse forearm view, the needle tip is in the
FCR, the target for injection. In this IP approach to the FCR, the needle must travel through
the palmaris longus to reach the FCR as is seen on the left hand side of the image.
Although an IP approach is often advocated and considered superior for most proce-
dures (11,12,18), this approach may be less optimal for some muscles or nerves during
chemodenervation procedures. This is due at least in part to the disadvantages of the
indirect approach, which is a disadvantage during chemodenervation procedures. To
compensate for the insertion distant to the transducer, the IP technique often requires a
longer, sometimes larger gauge needle. When using the IP approach, the clinician must
fi gure in the oblique path to the target when choosing a needle as additional needle
(a)
(b)
Figure 13.10 “In plane” approach with oblique needle angle resulting in a less hyperechoic needle
appearance.

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
119
length will be required to reach the target. The IP approach is used less frequently by
many clinicians performing US-guided chemodenervation procedures and is often
reserved for specifi c targets.
Also, during IP US-guided BoNT injections, the fi rst author has occasionally observed
the injectate fl ow out of the target along the needle track from the targeted muscle, into
the adjacent muscle or structure through which the needle has traveled to reach the
target. This typically occurs when using a large gauge needle, when quickly injecting
large volumes, when the target muscle is small or the patient has sustained involuntary
muscle contractions or spasms during injection. This potential spread of the toxin to
adjacent muscles is at least a theoretical risk for the cause of weakness that is sometimes
observed in nontargeted muscles (19–23).
Out of Plane Approach
The primary advantage of an OP approach, at least for chemodenervation procedures,
is that it may provide the most direct path to the target. OP is also superior to IP when
injecting superfi cial structures including many of the muscles targeted during BoNT
injections. The OP technique may not require the needle to pass through other muscles.
In addition, because the approach is more direct, a shorter, often thinner needle is used.
The main disadvantage to an OP approach is that the needle is viewed in cross sec-
tion, not along its long axis. This means only a small transverse section of the needle is
seen, that is, a hyperechoic dot. It must be remembered that both the needle tip and the
shaft will appear as a hyperechoic dot. If not performed carefully the needle tip may be
advanced beyond the transducer and be in an untargeted location (Figure 13.11). This
risk is minimized by carefully observing for movement in the tissue through which
the needle travels to the target. This movement should be carefully observed by the
clinician as the needle passes progressively from the superfi cial tissues through deeper
(a)
(b)
Figure 13.11 Out of plane technique: (a) needle tip inserted beyond US beam; (b) echogenic dot repre-
sents view of the needle shaft.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
120
tissues to the target. In this “walk-down” (11,24) technique the needle is pertubated, jig-
gled, or vibrated slightly throughout insertion to enhance the movement of the tissues
surrounding the bevel. (See DVD section for demonstration of walk down technique).
Other Techniques and Tips To Optimize Viewing of Needles
Etched or needles with a highly refl ective shaft are also available (Figure 13.12) but
usually not necessary or worth the additional cost. Of note, Tefl on-coated EMG injec-
tion needles may be less echogenic than standard needles and therefore less visible on
US in an IP approach. The Tefl on coating does not affect the visibility of these needles
using a walk down OP technique. Generally 27G to 25G hypodermic needles and EMG-
injecting electrode needles are easily visualized. Ultrathin 30G or higher needles used
for superfi cial injections may be more diffi cult to visualize but the movement in the tis-
sue described above will still be observed.
Techniques to maintain the correct needle/transducer angle during an IP approach
include tilting or heel-toeing the transducer, using a Standoff pad or fl oating the
transducer on a mound of gel (Figure 13.13). “Beam steering,” a feature on many US
machines, adjusts electronically, the angle of the US beam relative to a structure or a nee-
dle (Figure 13.14). Using this feature may enhance needle visualization by improving
the US beam/needle orientation angle. A biopsy or needle guide (Figure 13.15) can be
used and may sometimes be useful for less experienced clinicians but this technique is
less useful when the needle is inserted using a freehand approach.
INJECTION TECHNIQUES FOR BOTULINUM TOXIN THERAPY
Upper Limb Injections
Most muscles of the upper limb are easily viewed and injected with either a longitu-
dinal or transverse approach. The transverse body plane view often provides a better
view of the fascial planes between the muscles as well as neurovascular structures.
Figure 13.12 Etched needle.

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
121
Figure 13.15 Ultrasound biopsy guide.
(a)
(b)
Figure 13.13 (a) Stand off pads (b) Floating transducer on gel “pad.”
(a)
(b)
Figure 13.14 (a) Beam steering (b) US image showing needle with effect of beam steering.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
122
Focal Dystonia
For patients’ primary focal or segmental dystonia, virtually any muscle group may be
involved and require injection. B-mode US is used to identify and isolate individual
muscle fascicles for injection in focal dystonia. The patient is asked to move each fi nger
individually and movement in the muscle fascicles is observed directing the site for
injection. This technique is quick and simple and provides exquisitely accurate place-
ment of the toxin within an individual fascicle.
Upper Motor Neuron Conditions
Muscles commonly targeted for spasticity indications include proximal muscles acting
on the shoulder, elbow fl exors, wrist, fi ngers, or hand. When treating patients with upper
motor neuron syndromes the physician usually requires an assistant to maintain the limb
in an optimal position for injection therapy and to prevent involuntary movements.
Lower Limb Injections
Nearly all muscles of the lower limb including muscle of the pelvis, hip girdle, thigh,
and lower leg are easily visualized and targeted with US guidance. In obese patients
visualization of the muscles may be compromised by the depth of the overlying adipose
tissue. In this circumstance, US is still useful as it provides accurate depth assessment of
the fat and the depth of the adipose/muscle interface.
Primary Onset Segmental or Focal Dystonia
As in the upper limb, muscle involvement in these conditions is highly variable. Clinical
observation and functional assessment will direct the course of treatment.
Upper Motor Neuron Syndromes
Lower limb muscles most commonly targeted includ hip fl exors, adductors, knee fl exors/
extensors, ankle plantar fl exors/inverters, toe fl exors, and the extensor hallicus longus.
Head and Neck
Most of the target structures for toxin injection can be imaged with US. This includes
oromadicular muscles resulting in jaw opening, closing and eye closure. Salivary glands
are frequently targeted with the goal to reduce sialorrhea. A number of cervical muscles
and upper trunk muscles are easily identifi ed with US facilitating treatment of cervical
dystonia or abnormal neck position in children or adults with cerebral palsy.
SUMMARY
For clinicians to successfully implement US-guided chemodenervation techniques to
their practice requires a set of skills that are easily mastered with repeated practice.
While developing this profi ciency, physicians are encouraged to use US as an add-on

13. ULTRASOUND FOR PROCEDURAL GUIDANCE
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to the guidance techniques with which they are comfortable. For many physicians, US
largely replaces other guidance techniques once they have mastered this technology.
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over activity and spasticity. PM&R. 2009;1(9):842–851.
20. Bianchi S, Xamorani MP. US-guided interventional procedures. In: Bianchi S, Martinoli C eds. Ultrasound of the
Musculoskeletal System. Berlin, Heidelberg, New York: Springer; 2002:891–817.
21. Minamoto V, et al. Increased effi cacy and decreased systemic-effects of botulinum toxin A injection after active or pas-
sive muscle manipulation. Dev Med Child Neurol. 2007;49(12):907–914.
22. Naidu K, Smith K, Sheedy M, et al. Systemic adverse events following botulinum toxin A therapy in children with
cerebral palsy. DMCN. 2010;52(2):139–144.
23. Roche N, Schnitzler A, Genet F, et al. Undesirable distant effects following botulinum toxin A injections. Neurophrmacol.
2008;52(10);272–280.
24. Smith J, Finoff JT. Diagnostic and interventional musculoskeletal ultrasound part 2, fundamentals. PM&R.
2009;1(2):162–177.

Trunk
Katharine E. Alter, Steven Nichols, and Steven M. Skurow
When scanning, tissues are described by their echogenicity and internal echotexture. The
echogenicity of tissues in the human body are determined by their acoustic impedance.
When sound waves encounter tissue interfaces with very different acoustic impedance,
sound waves are highly refl ected (Figure 14.1). This creates a bright echo, described as
hyperechoic. When all the sound waves pass through tissues, travelling on to deeper
structures, no echoes are refl ected back to the transducer. As a result, the tissue will
appear black or anechoic. Tissues which weakly refl ect sound waves will have a rela-
tively hypoechoic appearance, that is, dark (Figure 14. 2) (1,2).
Body tissues have different echogenicity and a characteristic appearance based on
their acoustic impedance. For example, the mixed echotexture appearance of muscle
on ultrasound (US) scanning is distinct from the uniform echotexture of salivary or
thyroid glands (Figures 14.1 a,b and 14.3) The appearance of some tissues may also vary
with the scanning plane, that is, longitudinal or transverse, see muscle/nerve/tendon
description below. These tissue differences allow experienced clinicians to easily distin-
guish between the various tissue types encountered when using US to guide procedures
or during diagnostic scanning.
The tissues of interest for chemodenervation include muscle, nerve, tendon, vessels,
glands, as well as various organs which are to be avoided during procedures. The rele-
vant tissues will be described in detail.
MUSCLE
Muscle Architecture
Although there are three types of human muscle tissue (striated, smooth, and cardiac),
skeletal or striated muscle is the primary focus for the majority of chemodenervation
procedures. The US appearance of muscle is determined by the physical properties of
the fi bers, architectural organization of fi bers into fascicles, and the fascicular arrange-
ment of fascicles within a given muscle. Skeletal muscle is composed of individual cylin-
drical or prismatic fi bers, which are surrounded by a sarcolemma sheath; this in turn
is covered by the endomysium, a connective tissue layer (an extension of the perimy-
sium). The perimysium surrounds individual muscle fascicles, which are composed of
a bundle of muscle fi bers. Fascicles are also prismatic and are arranged either parallel to
or obliquely along the long axis of a muscle. The entire muscle is covered in epimysium,
which also surrounds the small vessels and nerves that supply and support the muscle.
14
Chemodenervation: Ultrasound
Characteristics of Relevant Tissues

14. CHEMODENERVATION: ULTRASOUND CHARACTERISTICS OF RELEVANT TISSUES
125
(a)
(b)
(c)
Figure 14.1 Mixed hyperechoic, hypoechoic echotexture of muscle. Transverse views: (a) biceps brachii,
(b) teres major, (c) medial gastrocnemius..
Figure 14.2 Anachoic Baker’s cyst
with posterior acoustic enhancement.
The width of individual fi bers (0.51 mm) is far less variable than the length which ranges
from 38 mm to over 60 cm (1).
All muscles have an origin, belly, and tendon of insertion. The organization of fi bers/
fascicles relative to the tendon will determine the appearance of a muscle. In fusiform
muscles, such as the biceps, the individual fi bers/fascicles curve or taper at either
end to the origin and tendon (Figure 14.4a). The muscle fi bers of quadrilateral mus-
cles such as the palmaris brevis or masseter run parallel to their tendon (Figure 14.4b).
Triangular muscles have a wide origin with fi bers converging to a thin tendon of inser-
tion (iliacus infraspinatus, supraspinatus).There are several types of pennate muscles
in which the feather-like fi ber arrangement of the fi bers is oblique to the line of pull

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
126
(a)
(b)
Figure 14.4 (a) Biceps longitudinal (b) masseter, longitudinal.
Figure 14.3 Uniform echotexture of
parotid gland.
of the muscle (Figure 14.5). There are several types of pennated muscles: unipennate
where fi bers attach along one side of a tendon (extensor digitorum longus) and triangu-
lar muscles such as the adductor longus. The deltoid is an example of a mutlipennate
muscle (Figure 14.6). In bipennate muscles, individual fi bers/fascicles run from either
side of a central tendon (rectus femoris, gastrocnemius) (Figure 14.5a). The tibialis ante-
rior is a circumpennate muscle where the fi bers/fascicles surround a central tendon
(Figure 14.7) (1,2). The architecture and pennation angle of these muscles infl uences
muscle biomechanics and increases the force generated by pennated muscles (2). The
fi ber/fascicle arrangements accounts for the distinct US appearance of individual mus-
cle types when scanning.

14. CHEMODENERVATION: ULTRASOUND CHARACTERISTICS OF RELEVANT TISSUES
127
(a)
(b)
(c)
Figure 14.5 (a) Gastrocnemius longitudinal, (b) gastrocnemius longitudinal 2, (c) longitudinal view
semimembranosis.
Figure 14.6 Deltoid, longitudinal.
(a)
(b)
Figure 14.7 (a) Longitudinal view tibialis anterior, (b) transverse view.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
128
US Appearance of Muscle
Because of their high water content, the contractile elements of the muscle fi ber/fascicle
are relatively hypoechoic when compared to the adjacent/surrounding connective tis-
sue (which is comparatively bright or relatively hyperechoic) (Figures 14.8 and 14.9).
Because the resolution of high frequency US is less than 1 mm and the width of muscle
fi bers is 0.51 mm, individual muscle fascicles can be visualized on US scans (when using
a high frequency transducer) (1–4). Muscle fascicles are best viewed in long axis where
they appear as long hypoechoic cylindrical structures (1–5). On a longitudinal image
scan, groups of fascicles will appear as separate linear hypoechoic structures inter-
spersed with hyperechoic connective tissue and may appear feather like. The various
fascicular arrangements account for the differences seen on US with the various muscle
fascicular arrangements (Figure 14.9). On transverse scans, individual fascicles are dif-
fi cult to discern, but with ultra-high frequency transducers they have the appearance
of a hypoechoic dot surrounded by a hyperechoic rim. In transverse view, the muscle
has a speckled or starry night appearance (Figures 14.1 a,b and 14.8) (1–4). Muscle is
anisotropic, but less so than tendons (2). The echotexture and sonographic appearance
of individual muscles is distinct, that is, the echotexture of the biceps is different than
the gastrocnemius or quadriceps (Figures, 14.1, 14.6–14.9).
(a)
(b)
(c)
Figurre 14.8 Transverse view: (a) triceps, (b) rectus femoris, (c) FDS.
(a)
(b)
(c)
Figure 14.9 Longitudinal view: (a) triceps, (b) rectus femoris, (c) semimembranosis.

14. CHEMODENERVATION: ULTRASOUND CHARACTERISTICS OF RELEVANT TISSUES
129
With contraction, all muscle fi bers shorten, thicken, and appear more hypoechoic.
The bulk of the muscle will also appear to increase as the muscle shortens. In pennated
muscles, the pennation angle, that is, the angle between the fi ber/fascicle and the apo-
neurosis increases (1,2). During contraction, motion in the fascicles is more apparent
on longitudinal scans. Histologically there are two types of muscle, type 1, slow twitch
or red and type 2, fast twitch or white. Type 2 fi bers are larger and have less myoglo-
bin than type 1 fi bers. Individual muscles are made up of a mix of fi ber types but spe-
cifi c fi ber types may predominate in certain muscles (2) or change with training (5).
Currently US cannot discriminate between type 1 or type 2 fi bers.
During US-guided procedures, experienced clinicians may recognize pathology, and
if so, should describe the observed abnormalities and comment on or report these fi nd-
ings. This may include partial or complete tears, muscle strains, hematomas, defects in
the fascia, or muscle herniation (3,4,6). When encountering an apparent abnormality,
comparison to the uninvolved side is always useful for confi rmation. In regards to mus-
cle pathology, advances in US technology in the last two decade including the addition
of quantitative techniques have revolutionized the diagnosis of neuromuscular disor-
ders. US can identify fasciculations, altered muscle characteristics, and changes asso-
ciated with neuropathies (6–10). It is now possible to accurately discriminate muscle
pathology on US imaging. For example, the appearance and echotexture of myopathic
muscle (Figure 14.10 a,b) is distinct from that of healthy muscle (Figure 14.10c). It is also
possible to discriminate between myopathic and neuropathic (Figure 14.10d) changes
in muscle with reported sensitivity for detecting any muscle change at 81% and speci-
fi city at 98% and higher sensitivity for neurogenic disorders (11). A detailed discussion
of diagnostic US imaging and the reporting of normal muscle and muscle pathology is
beyond the scope of this text.
TENDON
Tendons link muscle to a bone transmitting the force of contracture to the bone or joint.
Tendons are composed of tightly packed bundles of type 1 collagen arranged in well
ordered bundles and grouped into fascicles. The fascicles of tendons are most often
arranged longitudinal to the axis of the tendon but may assume a spiral or transverse ori-
entation. Type 1 tendons course directly to their insertion and are covered by paratenon.
Type 2 tendons cross a synovial joint before inserting and are covered by synovium (2).
This accounts for the differences seen in tendon pathology.
The US appearance of tendon, in a longitudinal view, is highly fi brillar due to the
tightly packed linear echoes that are produced by tendon fascicles. In transverse
view, the US appearance is that of multiple hyperechoic dots and “broom-end-like”
(Figure 14.11 a,b). In longitudinal view, tendon is highly fi brillar and hyperechoic
(Figures 14.12 a,b and 14.13 a,b). Tendons are highly anisotropic and therefore their
appearance varies with insonnation angle. Tendons are hyperechoic when viewed at
< 90° but may appear artifactually hypoechoic at angles < 90° (Figure 14.13 a,b,c) (1,2,4).
Rocking or heel-toeing the transducer is a technique used to adjust the US beam angle
and to better visualize the tendon at 90°, along its entire course (6). Intramuscular ten-
don may be seen as a hyperechoic band surrounded by the relatively hypoechoic muscle
tissue. In some muscles, such as the gastroc-soleus, the intramuscular tendons converge
to insert distally. Tendons, being solid structures, are not compressible and on Doppler
imaging normal tendons show no fl ow. In pathologic states, such as tendinopathy, color

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
130
(a)
(b)
(c)
(d)
Figure 14.10 Transverse view, rectus femoris: (a) rectus femoris, (b) congenital myopathy, (c) normal
muscle, (d) neurogenic atrophy.
(a)
(b)
Figure 14.11 Transverse view fl exor tendons/median nerve at wrist: (a) correct transducer orientation
at 90°, (b) oblique transducer position leading to anisotropy.

14. CHEMODENERVATION: ULTRASOUND CHARACTERISTICS OF RELEVANT TISSUES
131
(a)
(b)
Figure 14.12 Longitudinal view, fl exor tendons, median nerve, wrist: (a) correct transducer position/
beam angle, (b) incorrect transducer position/beam angle leading to anisotropy.
(a)
(b)
Figure 14.13 Longitudinal view tendon: (a) correct transducer position/beam angle, (b) incorrect trans-
ducer position/angle leading to anisotropy.
or power Doppler may reveal increased fl ow (Figure 14.14). This should not be con-
strued as infl ammation and may represent neovascularity (2,6). Tendon instability or
partial tears may be encountered during US-guided procedures and should be com-
mented on or reported if recognized. A full discussion of tendon pathology is beyond
the scope of this text.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
132
LIGAMENTS
Ligaments attach bones to other bones and like tendons, are composed of bundles of
collagen, and therefore are hyperechoic and somewhat fi brillar in appearance on longi-
tudinal scans. Ligaments are thinner and more compact than tendon and may be more
diffi cult to distinguish on scanning. The arrangement of the collagen bundles in liga-
ments is more variable than in tendon due to the multidirectional stresses applied to
ligaments. Ligaments can be distinguished from tendon by following the structure from
origin to attachment. The hyperechoic appearance of ligaments and their visualization
is enhanced when the ligament is stretched or stressed. Dynamic testing or stressing
may also reveal strains, partial or complete tears (1,3,4).
NERVES
Nerves are composed of bundles of axons arranged in fascicles, covered by supported
connective tissue including the endoneurium surrounding axons and epineurium sur-
rounding individual fascicles. The perineurium surrounds the nerve itself. Myelinated
nerves are covered or enveloped by Schwan cells. The internal structure of nerves may
be plexiform in proximal nerves and more cable like distally. Individual nerve axons run
the entire length of the nerve to their target of innervation. Nerves are supported by rich
blood supply which is required to provide energy use (1,6, 7, 12).
US echogenicity of axons and nerve fascicles is relatively hypoechoic surrounded by
hyperechoic supporting connective tissue of the epineurium and perineurium. In trans-
verse view, with a high frequency linear transducer, individual nerve fascicles are visu-
alized and have a honeycomb-like appearance (Figures 14.11 and 14.15). On longitudinal
scanning, the individual fascicles appear as linear, uninterrupted hypoechoic bands sur-
rounded by interrupted linear bands of supporting connective tissue (Figure 14.12a).
The US appearance of nerve on a longitudinal scan is sometimes described as appearing
like “railroad track” with the outer hyperechoic connective tissue and inner hypoechoic
fascicles. Nerves are often best observed in transverse view and can be traced proximal
Figure 14.14 Neovascularity quadri-
ceps tendon.

14. CHEMODENERVATION: ULTRASOUND CHARACTERISTICS OF RELEVANT TISSUES
133
to distal. Nerves and blood vessels often run together in a neurovascular bundle, adja-
cent to the muscles of interest (1,3,4,8,12). This relationship is useful when attempting
to identify or trace a nerve.
Nerves and tendon may have a similar appearance on US scanning. Distinguishing
between the two is important during chemodenervation procedures involving nerve
blocks. Nerves are slightly more compressible than tendons. Unlike tendons, nerves
have a fascicular internal pattern in both transverse and longitudinal views. Nerves are
less hyperechoic than tendon and do not have a fi brillar appearance on longitudinal
scans. With active (less so for passive) range of motion, tendons will move more than
nerves.
Nerve pathology may be identifi ed on US scanning including enlargement, focal com-
pression, or loss of continuity in a peripheral nerve injury. Decreased mobility of a nerve
at sites of entrapment and focal enlargement may occur. Sonopalpation or compression
of a nerve at the site of entrapment may increase or induce symptoms (1,3,4,8,12).
VESSELS
Both veins and arteries are distinguished from other structures because of the fl ow of
blood. Vessels vary in size from large femoral vessels to small intramuscular branches.
In transverse or longitudinal view, blood vessels appear anechoic or hypoechoic. In
transverse view, the vessels are usually circular or ovoid and in longitudinal scans
they appear tubular (Figure 14.16). Thin walled veins are easily compressible with
sonopalpation/compression. Vessels will reveal fl ow with color or power Doppler
(Figure 14.17). Documenting fl ow on Doppler imaging is useful to help distinguish
vessels, nerve, and tendons. As noted above, vessels and nerves frequently run
together.
Figure 14.15 Transverse view bra-
chial plexus at interscalene groove.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
134
BONE
Because bone is highly refl ective, sound waves are unable to penetrate below the cortical
surface the view of the underlying bone is limited. Because bone refl ects all or most of
sound back to the transducer, the bone cortex appears highly hyperechoic. A posterior
acoustic “shadow” is cast deep to bone or other calcifi ed structures (tendon, muscle)
limiting the view of structures that are “behind” these structures. Therefore ultrasound
imaging of bones is limited to the cortical surface (Figure 14.18 a,b,c).
Figure 14.16 Transverse view, cer-
vical region. Carotid and partially
compressed jugular deep to sterno-
cleidomastoid muscle.
Figure 14.17 Transverse view poste-
rior calf, posterior tibial vessels, color
doppler scan.

14. CHEMODENERVATION: ULTRASOUND CHARACTERISTICS OF RELEVANT TISSUES
135
US can provide information about acute fractures (cortical discontinuity) but is gener-
ally not the fi rst choice of imaging for suspected fractures. Superfi cial boney erosions can
be visualized as can step-off deformities or subperiosteal hematomas (13,14). Irregularity
of the boney surface at the attachment of tendons also suggests pathology. The bone cal-
lous created by stress fractures may appear hyperechoic on US scanning (15).
JOINTS
High frequency transducers provide information about superfi cial portions of the joint cap-
sule and may discriminate joint fl uid and cartilage. Three types of joints exist in the human
body: fi brous, synovial, and cartilaginous (3,16). US is more commonly used to visual-
ize synovial joints which are formed by articulated bones, fi brous capsule, ligaments, and
intra-articular structures such as menisci, fat pads, intra-articular ligaments, and labrum.
On US, the joint capsule appears as a linear hyperechoic structure that merges with the
surrounding para-articular soft tissues (17). Increasing evidence supports the effi cacy of
neurotoxin therapy on refractory joint pain and other musculoskeletal indications (18–23).
Familiarity with joints and the approach to joint injection may therefore be useful for physi-
cians providing chemodenervation procedures. See Chapter 16, “US-Guided Neurotoxin
(BoNT) Injections: Clinical Applications.”
GLANDS
In some patients, neurotoxins are useful for their neurosecretory blocking action (24–28).
While neurotoxins are effective in reducing sweating, US is generally not required for
these injections. Unless enlarged, sweat glands may not be visible. Salivary glands how-
ever are easily visualized with US and have a uniform homogenous echotexture similar
to thyroid tissue (Figure 14.3) (29). The homogeneity of glandular tissue with similar
appearance on both longitudinal and transverse views is unlike the mixed hypoechoic/
hyperechoic appearance of adjacent muscle, which has a very different appearance on
transverse and longitudinal views. Prostate is a mix of homogenous glandular compo-
nent and intraglandular smooth muscle. Detailed discussion of prostate and neurotoxin
therapy is beyond the scope of this text.
(a)
(b)
(c)
Figure 14.18 Transverse views of bone with posterior acoustic shadowing: (a) proximal femur head,
(b) distal radius, (c) distal tibia.

ULTRASOUND-GUIDED CHEMODENERVATION PROCEDURES
136
OTHER TISSUES
In general, “other tissues” are to be avoided during neurotoxin injections including
abdominal contents, lung, kidney, vessels, and so on. These structures often lie deep
or adjacent to a target of interest such as a muscle, nerve, or gland. One of the most
common structures to be avoided include viscera, when injecting the rectus abdo-
minis, interior/exterior abdominal oblique, or the iliacus (Figure 14.19 a,b). Renal
parenchyma is adjacent to the psoas muscle when using a posterior approach. The
hypoechoic apex of the lung is often just beneath the middle scalene and may be
avoided by using US guidance (30,31).
SUMMARY
There are many tissues in the body that are routinely investigated using US including
the tissues and structures relevant to chemodenervation, described above. These tis-
sues are discriminated by pattern recognition of their identifying features including
the echogenicity and echotexture. Many other body tissues are also routinely evalu-
ated with US including liver, spleen, kidney, heart, the infant brain, and others. Those
readers interested in more details are referred to the many available textbooks on US
medicine and scanning.
REFERENCES
1. O’Neill J. Introduction to musculoskeletal ultrasound. In: O’Neill J, Ed. Musculoskeletal Ultrasound, Anatomy and
Technique. New York, NY: Springer; 2008:1–17.
2. Pia Zamorani MP, Valle M. Muscle and tendon. In Bianchi S, Martinoli C, eds. Ultrasound of the Musculoskeletal
System. New York, NY: Springer; 2007:45–96.
(a)
(b)
Figure 14.19 (a) Superfi cial rectus abdominis muscle and bowel/abdominal contents; (b) iliacus at
anterior superior iliac spine.

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3. McDonald S, Fredericson M, Roh EY, et al. Basic appearance of ultrasound structures and pitfalls. Phys Med Clin N
Amer. 2010;21(8):462–479.
4. Smith J, Finoff JT. Diagnostic and interventional musculoskeletal ultrasound: part2. Clinical applications. PM&R.
2009;1:162–177.
5. Rennie CD, Hamilton SJ, Tarnopolsky MA. Changes in skeletal muscle in males and females following endurance
training. Can J Physiol Pharmacol. 2001 May;79(5):386-92.
6. Smith J, Finoff JT. Diagnostic and interventional musculoskeletal ultrasound part 1, fundamentals. PM&R.
2009;1:64–75.
7. Walker F. Imaging nerve and muscle with ultrasound. Adv Clin Neurophysiol. 2004;57:243–254.
8. Walker F. Neuromuscular ultrasound. Neur Clin. 2004;22(3):563–590, vi.
9. Pillen S, van Alfen N, et al. Muscle ultrasound: A grown-up technique for children with neuromuscular disorders.
Muscle & Nerve. 2008;38(3):1213–1214.
10. Boon A, Smith J, et al. Ultrasound applications in electrodiagnosis. PM&R. 2012;4(1):37–49.
11. Brockmann K, Becker P, et al. Sensitivity and specifi city of qualitative muscle ultrasound in assessment of suspected
neuromuscular disease in childhood. Neuromuscul Dis. 2007;17(7):517–523.
12. Valle M, Zamorani MP. Nerve and blood vessels. In: Bianchi S, Martinoli C, eds. Ultrasound of the Musculoskeletal
System. New York, NY: Springer; 2007:97–136.
13. Munk B, Bovig L, Droner K, et al. Ultrasound for diagnosis of scaphoid fractures. J Hand Surg. 2000;25:369–371.
14. Patten RM, Mack LA, Wang KY, et al. Nondisplaced fractures of the grater tuberosity of the numerous: Sonographic
detection. Radiology. 2001;220:231–235.
15. Jacobson JA. Fundamental of Musculoskeletal Ultrasound. Philadelphia, PA: Saunders Elsevier; 2007.
16. Erickson SJ. High resolution imaging of the musculoskeletal system. Radiology. 1997;23:406–406.
17. Zamori MP, Valle M. Bone and joint. In: In Bianchi S, Martinoli C eds. Ultrasound of the Musculoskeletal System. New
York, NY: Springer; 2007:137–185.
18. Singh, JA. Botulinum toxin therapy for osteoarticular pain: an evidence based review. Ther Adv Musculoskelet Dis.
2010;2(2):105–118.
19. Mahowald ML, Singh JA, Dykstra D. Long-term effects of botulinum toxin A for refractory joint pain. Neurotox Res.
2006;9:179–188.
20. Singh, JA, Mahowald ML, Kushnaryov A, et al. Repeat injection of intra-articular botulinumtoxin A for the treatment
of chronic arthritis joint pain-a case series review. J Clin Rheumatol. 2009;15:35–38.
21. Sing JS, Mahowald ML, Noorbaloochi S. Intra-articular botulinum toxin A for refractory shoulder pain: a randomized,
double blinded, placebo controlled trial. Transl Res. 2009;153(5):205–216.
22. Lee JH, Lee SH, Song SH. The effectiveness of botulinum toxin type B in the treatment of subacromial bursitis or
shoulder impingement syndrome. Clin J Pain. 2011;27(6):523–528.
23. Waseem Z, Boulias C, Gordon A, et al. Botulinum toxin injections for low-back pain and sciatica. Cochrane Database
Syst Rev. 2011;19(1):CD008257.
24. Lee JH, Lee BN, Kwon SO, et al. Anatomical localization of submandibular gland for botulinum toxin injection. Surg
Radiol Anat. 2010;32:945–949.
25. Ellies M, Laskawi R, Rohrbach-Volland S, et al. Botulinum toxin to reduce saliva fl ow: selected indications for ultra-
sound-guided toxin application into salivary glands. Laryngoscope. 2002;112(1):82–86.
26. Gerlinger I, Sxalai G, Hollody K, et al. Ultrasound-guided, intraglandular injection of botulinum toxin A in children
suffering from excessive salivation. JLO. 2007;121:947–951.
27. Ellies M, Laskawi R, Rohrbach-Volland S, Arglebe C. Up to date report of botulinum toxin therapy in patients with
drooling caused by different etiologies. J Oral Maxillofac Surg. 2003;61:454–457.
28. Meijer JW, van Kuijk AA, Geurts AC, et al. Acute deterioration of bulbar function after botulinum toxin treatment for
sialorrhoea in amyotrophic lateral sclerosis. Am J Phys Med Rehabil. 2008;87(4):321–324.
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Sjögren’s syndrome. J Rheum. 2008;35(2):285–293.
30. Nikoobakht M, Daneshpajooh A, Ahmadi H, et al. Intraprostatic botulinum toxin type A injection for the treatment of
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prostatic hyperplasia: early and long-term results. Urology. 2009;73(1):90–94.

Trunk
Katharine E. Alter and Michael C. Munin
Experienced injectors use a variety of guidance techniques when performing BoNT
chemodenervation procedures (1–3). Traditional techniques include palpation or using
anatomic reference guides/manuals many of which were designed for the purpose of
EMG (4–13). EMG may involve passive recording of a muscle at rest or may include
recording of EMG activity during muscle activation. When using E-Stim for chemod-
enervation, a stimulating hypodermic electrode is placed in muscle and stimulation is
applied. The needle is then advanced to a location resulting in contraction in the desired
muscle. High frequency US allows the injector to directly visualize the target. Some phy-
sicians also rely on motor point localization using published motor point maps, while
others combine two or more of the above techniques when performing chemodenerva-
tion procedures. Each of the above techniques has advantages and disadvantages. This
chapter will cover the advantages/disadvantages of the various techniques and address
questions that many clinicians ask including, “Why should I learn a new technique?”
and “Does US provide added benefi t?”
ANATOMIC GUIDANCE/PALPATION
All clinicians use anatomic guidance and palpation (AGP) for BoNT injections whether
in isolation or in combination with EMG, E-Stim, or US. A variety of surface anatomy
atlases and a number of articles detail anatomic localization techniques for needle inser-
tion for EMG or injection therapy exist. The majority of these atlases were written to
serve as reference guides when performing EMG (14–20).
Although AGP may seem to be the simplest, least complicated guidance technique
for chemodenervation, in reality it is the most technically challenging. This technique
demands the highest level of skill/experience because it relies on the examiners knowl-
edge of three dimensional anatomy and the ability to correctly estimate the location,
depth, and orientation of various muscles. While in some patients correctly identify-
ing a muscle target is facile, in most patients it is much more challenging (Figure 15.1).
Clinicians may falsely believe that targeting large muscles of the thigh or arm is less
challenging but evidence does not support this. Studies measuring the accuracy of blind
needle insertion for EMG reveal errors in correctly needling both upper and lower limb
muscles. Haig et al. in a 2003 lower limb cadaver study showed that the accuracy of
blind needle insertion in lower extremity muscles was 45%, overall, but varied from 0%
in repeated attempts to insert a needle into the hip fl exors to 100% in the vastus medialis
(21). The authors also reported that the needle pathway was very close to nontargeted
15
Comparing Guidance Techniques for
Chemodenervation Procedures

15. COMPARING GUIDANCE TECHNIQUES FOR CHEMODENERVATION PROCEDURES
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structures such as tendon, vein, artery, and nerve. Goodmurphy et al. also compared
blind needle insertions using two anatomic reference guides. They reported greater
accuracy in larger, superfi cial muscles of the lower extremity, and greater diffi culty in
accurately targeting other muscles (22). In a 2010 cadaver study, Boon et al. measured the
accuracy of blind versus US-guided fi ne wire placement in 14 lower extremity muscles
(23). For blind insertions they reported accuracy ranges from 0% for the rectus femoris
to 100% for the short head of the biceps femoris. For blind insertions, the more experi-
enced clinician only had a higher accuracy (compared to the inexperienced clinician)
when the results were pooled to include “accurate placement” and “placement deep
to the target.” The above studies all confi rm the diffi culties even experienced clinicians
experience when using blind targeting techniques.
In the forearm, leg or cervical regions, estimating muscle location/depth using AGP
is even more challenging because the complex overlapping orientation of muscles, may
be diffi cult to appreciate. Estimating muscle location or depth with AGP is also made
diffi cult by the wide variation in patient size and body composition encountered in clin-
ical practice. In patients who are obese, it is often impossible to palpate or estimate the
depth of muscles due to overlying adipose tissue. It is also diffi cult to estimate muscle
size and depth in patients who have muscle atrophy from disuse, neurologic disorders
or from the effect of repeated chemodenervation procedures. Additional factors that
Figure 15.1 Muscle identifi cation.