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Neuromuscular Ultrasound in Common Entrapment Neuropathies Michael S. Cartwright, MD, MS, and Francis O. Walker, MD November 2013 #54

Neuromuscular Ultrasound in Common Entrapment Neuropathies

Michael S. Cartwright, MD, MS

and Francis O. Walker, MD

Department of Neurology, Wake Forest University School of Medicine Main Floor Reynolds Tower

Winston-Salem, North Carolina

No one involved in the planning of this CME activity had any relevant financial relationships to disclose.

Reviewed and accepted by the 2012-2013 Monograph/Issues and Opinion Committee of the American Association of Neuromuscular & Electrodiagnostic Medicine

Certified for CME credit 11/2013 – 11/2016

Copyright© November 2013

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AANEM Monograph#54

CME STUDY GUIDE

AANEM Monograph #54 Neuromuscular Ultrasound in Common Entrapment

Neuropathies

Michael S. Cartwright, MD, MS

and Francis O. Walker, MD Department of Neurology, Wake Forest University School of Medicine

Main Floor Reynolds Tower Winston-Salem, North Carolina

EDUCATIONAL OBJECTIVES Upon completion of this monograph, the reader will acquire skills to: (1) describe basic

ultrasound findings in various common entrapment neuropathies and develop an understanding of the clinical utility of these tests, and (2) develop an understanding of the focal anatomy of the described entrapment neuropathies as it relates to ultrasonic findings.

CERTIFYING ORGANIZATION The American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) is

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NEUROMUSCULAR ULTRASOUND IN COMMON ENTRAPMENTNEUROPATHIESMICHAEL S. CARTWRIGHT, MD, MS and FRANCIS O. WALKER, MD

Department of Neurology, Wake Forest University School of Medicine, Main Floor Reynolds Tower, Winston-Salem, North Carolina,27157, USA

Accepted 4 May 2013

ABSTRACT: Neuromuscular ultrasound involves the use ofhigh-resolution ultrasound to image the peripheral nervous sys-tem of patients with suspected neuromuscular diseases. It com-plements electrodiagnostic studies well by providing anatomicinformation regarding nerves, muscles, vessels, tendons, liga-ments, bones, and other structures that cannot be obtainedwith nerve conduction studies and electromyography. Neuro-muscular ultrasound has been studied extensively over the past10 years and has been used most often in the assessment ofentrapment neuropathies. This review focuses on the use ofneuromuscular ultrasound in 4 of the most common entrapmentneuropathies: carpal tunnel syndrome, ulnar neuropathy at theelbow and wrist, and fibular neuropathy at the knee.

Muscle Nerve 48:696–704, 2013

Neuromuscular ultrasound is a rapidly evolvingfield in which high-resolution ultrasound is used todiagnose, prognosticate, and guide therapeutics inindividuals with neuromuscular conditions.1 Ultra-sound of muscle for diagnostic purposes was firstdescribed in the early 1980s in children with mus-cular dystrophy and spinal muscular atrophy.2 In1988, Fornage first described ultrasonographicexamination of peripheral nerves,3 and in 1991,Buchberger and colleagues were the first to assessthe accuracy of neuromuscular ultrasound for thediagnosis of a focal nerve disease, carpal tunnelsyndrome (CTS).4 Since then, over 100 articleshave been published on the use of neuromuscularultrasound for evaluation of focal entrapment neu-ropathies, and the aim of this report is to discussand summarize its use in 4 of the most commonentrapment neuropathies.

NEUROMUSCULAR ULTRASOUND STANDARDS

Evaluation of the peripheral nervous systemwith ultrasound is typically accomplished with ahigh-frequency (12–18 MHZ) linear array trans-ducer, although imaging of deeper structures,such as the proximal sciatic nerve, may require alower frequency transducer (2 to 6 MHZ) and a cur-vilinear interface (Fig. 1). The structure of interestshould always be imaged in at least 2 distinct planes,such as cross-sectional and sagittal, and imagesshould be stored (either printed or digitally). Alltransducers have a mark on one side of the trans-ducer which corresponds to a specific side of theultrasound screen (typically the left side, althoughthis setting can be changed). It is important for theultrasonographer to always position the transducerso the mark is toward the ultrasonographer’s leftwith cross-sectional imaging and toward thepatient’s head with sagittal imaging. This makes theinterpretation of published images more intuitive.

Nerve measurements, using the calipers builtinto the ultrasound device, are often obtained dur-ing the assessment of entrapment neuropathies.The most common measurement is of the cross-sectional area of the nerve. This is typicallyobtained by using the “free hand” drawing tool totrace along the hyperechoic (bright) epineurial

FIGURE 1. On the left is a 17 MHZ linear array transducer and

on the right is a 5 MHZ curvilinear transducer. The higher fre-

quency transducer on the left is more often used in neuromus-

cular imaging, but the lower frequency transducer may be

needed for deep structures, such as the proximal sciatic nerve.

Abbreviations: CTS, carpal tunnel syndromeKey words: clinical neurophysiology; fibular nerve ultrasound; mediannerve; ulnar nerve; entrapment neuropathyPublished 2013 American Association of Neuromuscular & Electrodiagnos-tic Medicine. Published by Wiley Periodicals, Inc. This article is a US Gov-ernment work and, as such, is in the public domain in the United Statesof America.

This monograph was reviewed and approved by committees of the Ameri-can Association of Neuromuscular and Electrodiagnostic Medicine. It didnot undergo further peer review by Muscle & Nerve.

Dr. Cartwright has funding from the NIH/NINDS (1K23NS062892) to studyneuromuscular ultrasound.

Correspondence to: M.S. Cartwright; e-mail: [email protected]

VC 2013 Wiley Periodicals, Inc.Published online 16 May 2013 in Wiley Online Library (wileyonlinelibrary.com).DOI 10.1002/mus.23900

696 AANEM Monograph MUSCLE & NERVE November 2013

rim of the nerve, erring to the inside of the rim(Fig. 2). Instead of the “free hand” technique,some use the “ellipse” program available with mostultrasound devices to fit an ellipse over the nerve,which then produces an area measurement. Ineither the cross-sectional or longitudinal view, thediameter of the nerve can be measured using the“straight line” tool. It is important to angle thetransducer so that it is perpendicular to the nervewhen obtaining the cross-sectional image, other-wise the area may be increased artificially (Fig. 3).Similarly, when measuring the diameter of a nervein the sagittal plane it is important that the trans-ducer be positioned to image through the thickestportion of the nerve, so a true diameter isobtained and is not lowered artificially (Fig. 3).

COMMON ULTRASOUND FINDINGS IN ENTRAPMENTNEUROPATHIES

When ultrasound was first used to evaluateentrapment neuropathies, it was thought that per-haps the most common finding would be nerve

flattening or pinching, but it was quickly realizedthis was not the case. While flattening or pinchingof the nerve can sometimes be identified withentrapment, the far more common and reproduci-ble finding is nerve enlargement just proximal tothe site of entrapment. This enlargement is typi-cally fusiform, rather than discretely focal, and it isimportant to identify the point of maximumenlargement when assessing the degree to whichthe nerve is enlarged (Fig. 4). The cutoffs mostcommonly used to define nerve cross-sectionalarea enlargement include: (1) an area more than2 standard deviations above the mean referencevalue, and (2) an area 1.5 times or greater than anunaffected portion of the same nerve.5 While thecause of nerve enlargement is not completelyunderstood, it is suspected to result from axoplas-mic damming, which is seen in models of entrap-ment and chronic nerve compression.6 Inaddition, there is likely an inflammatory and/orvascular component that contributes to nerveenlargement, as corticosteroids injected near an

FIGURE 2. The left and right images are the same, and they show a cross-sectional view of the median nerve at the wrist. The image

on the right shows the trace method that is used to obtain the nerve cross-sectional area.

FIGURE 3. (A) The cross-sectional area measurement of a nerve. The transducer on the left is perpendicular to the nerve, and the small-

est and most accurate cross-sectional area is depicted below the nerve. On the right the transducer is angled and not perpendicular, so

the area is artificially elongated and increased. (B) The nerve (oval) is seen in cross-section, and the transducer is placed to obtain a longi-

tudinal image of the nerve. The transducer on the left is placed correctly to image the middle of the nerve, which results in an accurate

diameter. The transducer on the right is incorrectly off-center, which artificially lowers the measured diameter of the nerve.

AANEM Monograph MUSCLE & NERVE November 2013 697

enlarged nerve can reverse some degree ofenlargement within a week of injection.7,8

While nerve enlargement just proximal to thesite of entrapment is the most common ultrasono-graphic finding detected in entrapment neuropa-thy, other findings have been reported. Theseinclude changes in nerve echotexture (theybecome hypoechoic), shape (flattening and pinch-ing at site of entrapment), fascicle size (enlarge-ment of single or multiple fascicles within thenerve), and vascularity (increased within thenerve).8–10 Changes in nerve mobility are alsoreported with entrapment, but these are not

uniform; there is decreased mobility in CTS andpossibly increased subluxation in ulnar neuropathyat the elbow.11,12

Structures near the nerve of interest should beassessed with ultrasound to determine if there areanatomical explanations for the entrapment, suchas cysts, tumors, aberrant muscles, etc. In addition,chronically denervated muscle may become hyper-echoic and atrophied, so imaging of muscles distalto the entrapment, both those innervated by theaffected nerve and innervated by unaffectednerves, can be informative.

Now that ultrasonographic standards and typi-cal findings in entrapment neuropathies have beendescribed, the rest of this review will focus on theneuromuscular ultrasound evaluation of 4 of themost common entrapment neuropathies.

MEDIAN MONONEUROPATHY AT THE WRIST

The most common entrapment neuropathy isof the median nerve at the wrist, which causesCTS. The mean annual crude incidence of CTS is329 per 100,000 person-years, and more thanthree-quarters of the cases involve women.13 It is acommon work-associated condition, and healthcarecosts in the United States alone exceed $500 mil-lion per year.14,15 Median mononeuropathy at thewrist is also the entrapment neuropathy studiedmost frequently with ultrasound, and the ultraso-nographic evaluation of this condition is describedbelow.

Patient Position. Arranging the patient in a posi-tion that is comfortable for both patient and exam-iner is important for all ultrasonographic studies(Fig. 5). For the assessment of median mononeur-opathy at the wrist, the patient can be eithersupine or seated with palms upward and resting onthe lap or a pillow across the lap. The supine posi-tion may be more comfortable for the patient,

FIGURE 4. A nerve running under a ligament causing chronic

compression is depicted. When chronic entrapment occurs,

nerves develop fusiform enlargement rather than discrete

enlargement. Therefore, it is important to measure the nerve at

the site of maximum enlargement, which is level C in this image.

FIGURE 5. The images show the 2 options for patient positioning during neuromuscular ultrasound of the wrist. The supine position

may provide greater patient comfort, and the seated position allows for more efficient bilateral studies.


particularly for longer examinations, but theseated position allows for more efficient evaluationof both wrists in cases of bilateral median mono-neuropathy at the wrist. The seated position alsoallows patients to observe the study, which someappreciate.

Transducer Position. To obtain a sagittal view, thetransducer is aligned with the thenar crease (whichtypically also aligns with the middle finger) and isplaced at the wrist (Fig. 6). To obtain a cross-sectional view, the transducer is rotated 90 degreesand aligned with the distal wrist crease. Finally, toobtain a proximal cross-sectional area for compari-son, the transducer is started at the wrist and thenerve is traced proximally to the mid-forearm,where it lies deep to the flexor digitorum superfi-cialis muscles and superficial to the flexor digito-rum profundus muscles.

Reference Values. Many different reference valueshave been published over the past 10 years formedian nerve cross-sectional area at the wrist. Sev-eral studies, including a meta-analysis, suggest thata cutoff of greater than 10 mm2 is sensitive for thediagnosis of CTS, whereas others use a more spe-cific cutoff of greater than 12 mm2.9,16 A wrist-to-forearm area ratio of greater than 1.4 is also sensi-tive and specific for diagnosis of CTS.5 Just as withnerve conduction studies, it is recommended thateach lab generate its own reference values for thenerves evaluated commonly.

Typical Neuromuscular Ultrasound Findings. Enlarge-ment of the median nerve cross-sectional area atthe distal wrist crease is an accurate parameter fordiagnosis of CTS, with sensitivity and specificitygreater than 85% in several studies.17,18 Not as wellcharacterized is the echotexture change that accom-panies CTS. The median nerve at the distal wristcrease often becomes hypoechoic as it enlarges, butthe accuracy of this finding is not known.8

Findings Unique to This Entrapment Syndrome. Ofinterest, the median nerve in individuals with CTS

has decreased mobility compared with healthy con-trols, and the decreased movement can be quanti-fied in both lateral and distal–proximal planes.11,19

In our lab, a grading scale is used to assess mediannerve movement in those with suspected CTS(Table 1). Another neuromuscular ultrasoundfinding that has only been studied systematically inCTS is increased nerve vascularity, as detected withDoppler ultrasound. Some studies have reportedthis to be a very powerful parameter for diagnosisof CTS, with accuracy greater than 95%,10 butmachine settings and operator dependence likelyresult in a lower accuracy during routine clinicaluse.

Approximately 10–15% of all individualsassessed with neuromuscular ultrasound have bifidmedian nerves at the wrist, and 5–10% have persis-tent median arteries running through the carpaltunnel (these conditions sometimes, but notalways, occur together) (Fig. 7).20,21 Bifid mediannerves and persistent median arteries are not morecommon in CTS, but they can change the thera-peutic approach, especially the presence of a largepersistent median artery.20 Other anatomic abnor-malities that have been identified with neuromus-cular ultrasound as causing or mimicking CTSinclude traumatic neuromas, Schwannomas, lipofi-bromatous hamartomas, ganglion cysts,

FIGURE 6. (A) A sagittal view of the median nerve at the wrist. (B) A cross-sectional view. (C) A cross-sectional view in the forearm. Arrow,

median nerve; C, carpal bones; T, flexor tendons; FDS, flexor digitorum superficialis muscles; FDP, flexor digitorum profundus muscles.

Table 1. Grading median nerve movement at the wrist.*

Grade Mobility assessmentDescription of

nerve movement

0 Decreased The median nerve has minimalmovement in all directions.

1 Slightly decreased The median nerve moves freelyin the transverse plane butdoes not dive deep.

2 Normal The median nerve dives deepand is surrounded on all sidesby the flexor tendons.

*The patient is asked to repeatedly flex and extend the fingers and wristwhile the ultrasound transducer is held still. The grades described in thetable are used to describe the degree of median nerve movement.


thrombosed persistent median arteries, abscesses,and compressive gouty tophus.22–25

ULNAR NEUROPATHY AT THE ELBOW

The mean crude annual incidence of ulnarneuropathy at the elbow is 24.7 per 100,000person-years, which is approximately 1/13th ascommon as median neuropathy at the wrist in thesame population.13,26 More than two-thirds of casesinvolve men,26 and the neuromuscular ultrasoundevaluation of this condition is described below.

Patient Position. Two positions can be used(Fig. 8). One is with the patient supine and thearm abducted and flexed at the elbow. This is simi-lar to the position used for ulnar nerve conductionstudies, and it allows for evaluation of the nervefrom the wrist to the axilla, dynamic evaluationduring full flexion and extension of the elbow,and reduced redundancy in the skin or ulnarnerve that may occur when the arm is straight.The other position is with the patient seated, thearm internally rotated, and the palm flat on the

examination table. The ultrasonographer sitsbehind the patient in this arrangement.

Transducer Position. To obtain a sagittal view, thetransducer is placed in the ulnar groove (Fig. 9). Itcan then be rotated 90 degrees to obtain a cross-sectional view at the elbow. The transducer is thenadvanced distally to the mid-forearm and proxi-mally to the mid-arm, which allows for imaging ofthe nerve in the cubital tunnel, at the level of themedial epicondyle, and in the supracondylarregion, which are the main sites of maximumenlargement in ulnar neuropathy at the elbow.27

This also allows for ulnar nerve cross-sectional areameasurements at unaffected sites below and abovethe elbow, which can then be compared with thesite of maximum enlargement to generate a ratio.

Reference Values. Different reference values havebeen published over the past 10 years, with theupper limit of normal for the ulnar nerve at all sitesnear the elbow typically around 9–10 mm2.28–30 Aratio of the site of maximum enlargement compared

FIGURE 7. The left image shows a bifid median nerve, and the right image shows a persistent median artery (Power Doppler identifies

flow in the artery). Arrow, median nerve; curved arrow, persistent median artery; C, carpal bones; T, flexor tendons.

FIGURE 8. Positioning for ulnar nerve imaging. The left image shows the patient supine, which may be more comfortable, allow for

examination from the wrist to the axilla, and allow for dynamic evaluation during elbow flexion and extension. The right image shows

the patient in the seated examination position.


with an unaffected site greater than 1.4 also has highdiagnostic accuracy.27

Typical Neuromuscular Ultrasound Findings.

Enlargement of the ulnar nerve is the most com-mon finding; one of the largest series notedenlargement to be 80% sensitive and 91% specificfor the diagnosis.31 A ratio of the site of maximumenlargement compared with an unaffected sitegreater than 1.4 yielded sensitivity and specificitygreater than 95%, but that study was limited byspectrum bias.27

Findings Unique to This Entrapment Syndrome.

Hypermobility of the ulnar nerve, which results inthe nerve snapping over the medial epicondyle,has long been suspected to increase the risk ofulnar neuropathy at the elbow. Subluxation (whenthe nerve moves superficial to the medial epicon-dyle) and luxation or complete dislocation (whenthe nerve exits the groove and lies anterior to themedial epicondyle) with elbow flexion are easilyidentified and characterized with ultrasound.32 Sev-eral studies have examined this phenomenon withultrasound to determine if it occurs more often inthose with ulnar neuropathy at the elbow than incontrols, and the answer remains uncertain,although subluxation does occur frequently in

healthy controls.12,33 We use ultrasound to assessfor ulnar nerve hypermobility in cases of ulnarneuropathy at the elbow, as information about thiscondition may affect nerve conduction studies andsurgical planning.32

ULNAR NEUROPATHY AT THE WRIST

Unfortunately, there are no epidemiologic stud-ies to determine the prevalence or incidence ofulnar neuropathy at the wrist, but it is likely to bemuch less common than median mononeuropathyat the wrist and ulnar neuropathy at the elbow. Inaddition, it is thought more often to be secondaryto anatomic abnormalities such as trauma, gan-glion cysts, and thrombosed ulnar arteries, and itis also more common in those with CTS.7,8 Theneuromuscular ultrasound evaluation of this condi-tion is described below.

Patient Position. Positioning is the same as forevaluation of suspected CTS, so the patient can beeither supine or seated with the elbows flexed andpalms upward (Fig. 5).

Transducer Position. To obtain a sagittal view thetransducer is placed on the wrist over the ulnarartery, and once the artery is identified the trans-ducer is moved just medial (Fig. 10). The sagittalview of the ulnar nerve is challenging. The

FIGURE 9. A sagittal image of the ulnar nerve at the elbow is demonstrated on the left. The right image shows a cross-sectional view

of the ulnar nerve at the elbow. Arrow, ulnar nerve (in both images); ME, medial epicondyle; O, olecranon process.

FIGURE 10. The left image shows the ulnar nerve at the wrist in sagittal view, and the right image demonstrates the cross-sectional

view. Arrow, ulnar nerve; curved arrow, ulnar artery; P, pisiform bone; ADM, abductor digit minimi muscle.


transducer can be rotated 90 degrees, and theulnar nerve can be identified as a round or ovalstructure medial to the pulsatile artery. The trans-ducer is then moved proximally and distally 1–2cm in each direction to identify the site of maxi-mum enlargement.

Reference Values. The upper limit of normal forthe cross-sectional area of the ulnar nerve at thewrist is 8 mm2,28 but the diagnostic utility of thiscutoff in the rare entity of idiopathic ulnar neu-ropathy at the wrist has not been assessed.

Typical Neuromuscular Ultrasound Findings. Idio-pathic ulnar neuropathy at the wrist is rare, andtherefore there are no systematic studies of typicalulnar nerve findings in this condition. However, aswith other entrapment syndromes, it is thoughtthat the ulnar nerve enlarges with entrapment atthe wrist and may become hypoechoic.

Findings Unique to this Entrapment Syndrome.

Ulnar neuropathy at the wrist often occurs second-ary to an anatomic abnormality. Case reports andseries exist describing compressive ganglion cystsand dilated or thrombosed ulnar arteries.34,35 Inulnar neuropathy at the wrist, it is important toadvance the transducer distally, visualizing the pisi-form bone and the ulnar nerve just distal to thepisiform bone, as pathology can arise from thissite.

FIBULAR NEUROPATHY AT THE KNEE

As with ulnar neuropathy at the wrist, no com-prehensive epidemiologic studies exist regardingthe prevalence of fibular neuropathy at the knee,but it is thought to be the most common entrap-ment syndrome of the lower extremity.36 Condi-tions such as habitual leg crossing and squatting,dramatic weight loss, casting, and immobility

increase the risk of fibular neuropathy at theknee.37 The neuromuscular ultrasound evaluationof this condition is described below.

Patient Position. The fibular nerve can be eval-uated with the patient prone or supine, but the lat-eral decubitus position allows for the mostcomprehensive evaluation of the nerve, from theseparation from the sciatic nerve to the point ofcrossing over the fibular head (Fig. 11).

Transducer Position. Imaging can begin at eitherthe level of the distal sciatic nerve or over the fibu-lar head (Fig. 12). Obtaining a sagittal view of thefibular nerve as it travels near the fibular head ischallenging, as the nerve runs at an angle. In thecross-sectional view, the fibular nerve should beimaged from the sciatic nerve to at least the fibularhead, and possibly distal to that point, where itsplits into the superficial and deep fibular nerves.

Reference Values. A few studies have provided ref-erence values for the cross-sectional area of the fib-ular nerve, and in general the upper limit ofnormal for this nerve in the popliteal fossa and atthe fibular head is approximately 20 mm2.38 Thecross-sectional area of the fibular nerve is typicallyone-third that of the sciatic nerve and half that ofthe tibial nerve in the popliteal fossa.

Typical Neuromuscular Ultrasound Findings.

Enlargement of the fibular nerve near the fibularhead has not been studied systematically in casesof idiopathic mononeuropathy at this site,although decreased echogenicity has beendescribed in a small cohort of patients with fibularmononeuropathy at the knee associated withweight loss.39 Potential abnormalities in mobilityand vascularity have not been explored.

Findings Unique to this Entrapment Syndrome. Someindividuals with foot drop secondary to fibularneuropathy at the knee have intraneural ganglioncysts, which are crucial to identify, as they change

FIGURE 11. Patient positioning for imaging the fibular nerve at

the knee. The patient is in the left lateral decubitus position for

imaging the right fibular nerve.

FIGURE 12. The fibular nerve at the fibular head, in cross-

section. Arrows, fibular nerve; FH, fibular head.


medical management (Fig. 13). This finding is rel-atively common; it has been reported to occur in18% of individuals with electrodiagnostically con-firmed fibular neuropathy at the knee.40 Intraneu-ral fibular ganglion cysts should be suspected inpatients without habitual leg crossing, squatting,weight loss, or immobility.41 The cysts likely arisesecondary to acute or chronic trauma to the proxi-mal tibiofibular joint, which then allows synovialfluid to track along the intra-articular branch ofthe fibular nerve and back to the common fibularnerve.42 The cysts can be quite extensive, extend-ing to the level of the sciatic nerve, and on occa-sion even crossing into the tibial portion of thesciatic nerve.42 Surgical drainage of the intraneuralcysts typically results in resolution of symptoms,and repair of the proximal tibiofibular joint andligation of the intra-articular nerve branch preventsre-accumulation of the cyst.42

It has been proposed that some cases of idio-pathic fibular neuropathy at the knee may be sec-ondary to compression of the nerve between thetendon of the biceps femoris and the lateral headof the gastrocnemius.43 Therefore, a dynamic eval-uation of the fibular nerve at this site, with flexionand extension of the knee, can assist in diagnosingthe specific anatomic site of compression, althoughthis theory has not been studied systematically.

CONCLUSIONS

Neuromuscular ultrasound of common entrap-ment neuropathies provides diagnostic informa-tion that complements the history, physicalexamination, and electrodiagnostic studies. Neuro-muscular ultrasound has also advanced our under-standing of entrapment neuropathies andimproved treatment strategies, by demonstratingrelatively common conditions such as intraneuralganglion cysts in the fibular nerve. Intensive study

of neuromuscular ultrasound has only occurredover the past decade, so as more experience isgained, techniques are refined, and ultrasoundtechnology advances, it is likely the technique willcontinue to gain importance in evaluation ofentrapment neuropathies as well as a wide varietyof other neuromuscular diseases.

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FIGURE 13. An intraneural ganglion cyst of the fibular nerve.

This cyst extended from the level of the fibular head to the point

where the fibular and tibial nerves join to become the sciatic

nerve. Note that the cyst is round, anechoic, and has posterior

acoustic enhancement. Arrow, ganglion cyst; FH, fibular head.


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aanem monograph · the nerve is enlarged (fig. 4). the cutoffs most commonly used to deﬁne nerve...

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