AJR 2004; 182:123-129
© American Roentgen Ray Society
Sonography of Peripheral Nerve Pathology
R. M. Stuart1,
E. S. C. Koh1 and
W. H. Breidahl1,2
1 Department of Diagnostic and Interventional Radiology, Royal Perth Hospital,
GPO Box X2213, Wellington St., Perth 6847, Western Australia.
2 Perth Radiological Clinic, 127 Hamersley Rd., Subiaco, Perth 6008, Western
Australia.
Received July 15, 2002;
accepted after revision May 14, 2003.
Address correspondence to W. H. Breidahl
(billbrei{at}perthradclinic.com.au).
Introduction
In 1988, Fornage [1]
produced the first review of imaging findings of peripheral nerves using
sonography. Continual technologic improvements, including the availability of
high-frequency transducers (6-13–MHz) and variable footprint sizes, have
led to an increase in the use of sonography in the imaging of peripheral
nerves
[2–4].
We believe that sonography should be the primary technique for imaging
peripheral nerve pathology because it is inexpensive and widely available, has
no contraindications, and allows rapid, detailed imaging of the entire length
of the major peripheral nerves of both
limbs.
,
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Fig. 1B. —31-year-old man with normal median nerve. Longitudinal
5-12–MHz sonogram shows multiple longitudinal hypoechoic bands,
representing fascicular bundles (arrows). Note hyperechoic
discontinuous bands separating bundles that correspond to surrounding
intervening epineurium.
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In our practice, we routinely use a 5-12–MHz linear array transducer
(HDI 5000, ATL, Bothell, WA) to scan the entire peripheral nerve in both
transverse and longitudinal planes. Normal peripheral nerves have a typical
sonographic appearance, showing multiple longitudinal hypoechoic bands, which
represent fascicular bundles. These are separated by discontinuous bands of
increased echogenicity, corresponding to the surrounding epineurium
[1,
3]
(Fig. 1A). In this article, we
describe the sonographic appearances of normal peripheral nerves and important
examples of peripheral nerve disorders.
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Fig. 1A. —31-year-old man with normal median nerve. Photomicrograph of
histologic section of normal median nerve shows multiple nerve fibers (axons)
with accompanying Schwann cells. Myelin sheaths are bound together by thin
collagen strands called endoneurium. This group of fibers represents a single
fascicle, which is ensheathed by further dense connective tissue, perineurium
(arrow). Epineurium (E) is thick outer interdigitating connective
tissue, which surrounds multiple fascicles to form peripheral nerve.
Histologic correlation has shown that number of hypoechoic bands seen at
sonography does not correlate exactly with number of fascicles
[2].
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Focal Intrinsic Neural Lesions
Neural Fibrolipoma
Neural fibrolipoma is a disorder of unknown origin that causes infiltration
of the perineurium and epineurium with fibrofatty tissue. More than 80% of
cases involve the median nerve, although the brachial plexus, ulnar, radial,
and peroneal nerves may also be affected. When neural fibrolipoma is
associated with unilateral macrodactyly, it is termed "macrodystrophia
lipomatosa" and tends to affect the second or third digit of the hand or
foot. There is extensive fatty infiltration of the nerve and the whole digit,
with accompanying osseous overgrowth. Sonography shows thickened alternating
hyperechoic and hypoechoic bands, reflecting the fibrofatty infiltrate
[2,
3] (Fig.
2A,
2B).
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Fig. 2A. —13-year-old girl with neural fibrolipoma of median nerve.
Transverse 5-12–MHz sonogram shows enlarged hypoechoic fascicles
separated by extensive echogenic (fatty) infiltrate (arrows).
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Fig. 2B. —13-year-old girl with neural fibrolipoma of median nerve.
Axial T1-weighted image (TR/TE, 500/14) shows cablelike thick hypointense
bands separated by abundant fatty tissue, all of which are diagnostic of
neural fibrolipoma.
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Traumatic Neuroma
Traumatic neuromas are proliferative masses that represent a disorganized
attempt at nerve regeneration. They are often clinically palpable as small,
firm, tender masses. Spindle neuromas are a focal fusiform mass occurring in
intact nerves caused by chronic irritation. Terminal (amputation) neuromas
result from partial or complete transection of the nerve and arise at the
proximal nerve end. The most common site of occurrence is in the lower limbs
after surgical amputation. Because of their fibrous capsule, traumatic
neuromas are usually well defined and hypoechoic with attenuation
characteristics similar to muscle
[1,
3] (Figs.
3 and
4A,
4B).
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Fig. 4A. —30-year-old man with pain after forearm amputation for
undifferentiated sarcoma. Compound transverse 5-12–MHz sonogram of
proximal forearm shows three enlarged, well-defined, ovoid hypoechoic masses
at amputated ends of ulnar (thin black arrow), median (thick
black arrow), and superficial branch of radial (white arrow)
nerves.
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Fig. 4B. —30-year-old man with pain after forearm amputation for
undifferentiated sarcoma. Longitudinal 5-12–MHz image of central-most of
three hypoechoic masses shows median nerve (straight arrow) extending
to neuroma (curved arrow). Follow-up imaging (not shown) at 6 months
revealed no change.
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Morton's Neuroma
The term "Morton's neuroma" is a misnomer that describes a
benign mass of perineural fibrosis involving a plantar digital nerve lying
between two metatarsal heads. Morton's neuromas may be multiple and bilateral
and most commonly occur between the heads of the third and fourth metatarsals;
they are likely to develop because of friction of the nerve against the
transverse intermetatarsal ligament. On sonography, an ovoid hypoechoic
compressible mass is visible in the intermetatarsal space
[2,
3]
(Fig. 5). Fluid within the
intermetatarsal bursae is a common associated finding affecting the first
three web spaces that may also be seen on sonography
[5].
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Fig. 5. —24-year-old woman with surgically excised Morton's neuroma.
Preoperative longitudinal 5–12 MHz sonogram shows discrete oval
hypoechoic mass (open arrows), lying between metatarsal heads.
Digital nerve (solid arrow) can be seen proximal to mass.
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Intraneural Perineuroma
Intraneural perineuroma is a rare focal neural lesion that causes a slowly
progressive painless mononeuropathy. Histologic and cytogenetic analyses
reveal onion bulb–shaped whorls of neoplastic perineural cell
proliferation. The region of the peripheral nerve abnormality can be
determined using electromyography and nerve conduction studies
[6]. Sonography shows the
lesion to be hypoechoic, with mildly elongated fusiform enlargement of the
involved nerve (Fig. 6A,
6B).
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Fig. 6A. —34-year-old man with intraneural perineuroma diagnosed after
surgical biopsy. Longitudinal 5-12–MHz sonogram shows fusiform
hypoechoic swelling of right common peroneal nerve (arrows).
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Fig. 6B. —34-year-old man with intraneural perineuroma diagnosed after
surgical biopsy. Axial STIR MRI shows intraneural perineuroma of common
peroneal nerve at level of proximal popliteal fossa, with enlarged
hyperintense fasciculi (open arrow) between biceps femoris muscle (B)
and lateral head of gastrocnemius muscle (G). Compare with healthy tibial
nerve (solid arrow) between veins.
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Peripheral Nerve Sheath Tumors
The benign peripheral nerve sheath tumors that are most commonly described
are the schwannoma and the neurofibroma. Schwannomas are encapsulated tumors
that grow eccentrically along the nerve axis, within the epineurium, thus
often allowing the tumor to be surgically excised without loss of neurologic
function. Neurofibromas most commonly arise sporadically, either in a diffuse
cutaneous form or as a solitary peripheral nerve tumor. The plexiform
neurofibroma is a rarer neoplasm that typically infiltrates the fascicular
bundles of large nerve trunks and is virtually pathognomonic of
neurofibromatosis 1. These tumors are surgically inseparable from the host
nerve and can undergo malignant transformation
[1–3].
Sonography is unreliable in distinguishing between schwannomas and
neurofibromas; both appear as discrete homogeneous ovoid hypoechoic masses,
with a healthy nerve at the proximal and distal aspects of the mass
(Fig. 7). The presence of
cystic degeneration favors schwannoma rather than neurofibroma
[1–3]
(Fig. 8).
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Fig. 7. —32-year-old man with schwannoma. Longitudinal composite
5-12–MHz sonogram of ulna nerve in upper arm shows elongated hypoechoic
mass with healthy nerve entering and exiting tumor (arrows).
Diagnosis was confirmed at open biopsy.
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Malignant peripheral nerve sheath tumors arise from the transformation of a
plexiform neurofibroma in neurofibromatosis 1 in 50% of cases, although
previous radiotherapy can induce the development of these rare and highly
malignant tumors. On sonography, they appear as hypoechoic lesions, often with
indistinct margins [3].
Nerve Entrapment
As peripheral nerves pass through fibroosseous tunnels, they are vulnerable
to compression from a variety of extrinsic causes: congenital, traumatic,
synovitis, infiltration, ganglia, tumor, and other acquired disorders. Neural
compression leads to ischemia and venous congestion. If chronic, this may
cause fibrosis and loss of nerve function with atrophy of the innervated
musculature. Clinical manifestations and nerve conduction studies generally
give the diagnosis. However, in atypical cases, sonography can show causative
extrinsic abnormalities at the site of compression, with associated changes in
nerve contour and echotexture
[2,
4,
7]. The peripheral nerves that
sonography can evaluate in entrapment syndromes include the suprascapular,
median, ulnar, radial, sciatic, tibial, and common peroneal nerves (Figs.
9A,
9B,
10A,
10B,
11).
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Fig. 9B. —43-year-old man with ulnar neuritis. Sonogram obtained at
same magnification shows normal calibre of contralateral left ulnar nerve
(arrow) for comparison with A. Symptom relief followed ulnar
nerve decompression.
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Fig. 10A. —31-year-old male bus driver with pronator teres syndrome.
Transverse 5-12–MHz sonogram shows aberrant path of right median nerve
(straight arrows) through humeral head of pronator teres with deep
fascia inferiorly (curved arrow).
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Fig. 10B. —31-year-old male bus driver with pronator teres syndrome.
Sonogram shows normal left median nerve at same level (straight
arrows) passes beneath humeral head of left pronator teres with deep
fascia again shown (curved arrow). Recent change to driving new bus
corresponded to onset of symptoms that resolved on return to driving old
bus.
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Nerve Dislocation
As it courses behind the posterior aspect of the elbow, the ulnar nerve
normally lies in the cubital tunnel. During elbow flexion, sonography can be
used to scan dynamically, showing ulnar nerve dislocation; the nerve becomes
displaced around and anterior to the tip of the medial epicondyle on flexion
of the elbow (Fig. 12A,
12B). Sonography can also
differentiate ulnar nerve dislocation from other causes of medial elbow pain
and ulnar nerve neuropathy, such as cubital tunnel syndrome and snapping
triceps syndrome [8].
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Fig. 12A. —34-year-old man with ulnar nerve dislocation. Transverse
5-12–MHz sonogram of cubital tunnel using small footprint probe shows
ulnar nerve (open arrow) lying in normal position within sulcus,
lateral to medial epicondyle (solid arrow) when elbow is
extended.
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Fig. 12B. —34-year-old man with ulnar nerve dislocation. Transverse
5-12–MHz sonogram obtained with elbow flexion shows that ulnar nerve
(curved arrow) dislocates anteromedially out of sulcus (straight
arrow).
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Muscle Changes Resulting from Nerve Pathology
Denervating neuromuscular disorders typically result in soft-tissue and
muscle atrophy; this is associated with loss of muscle bulk and fatty
infiltration. Causes include acute brachial neuritis and quadrilateral space
syndrome. Pseudohypertrophy represents a combination of true muscle
hypertrophy and an increase in intramuscular connective tissue and fat.
Pseudohypertrophy frequently occurs in the calf muscles, and this phenomenon
is seen in some dystrophic muscle conditions, hemihypertrophy syndromes, and
chronic neuropathies. True muscle hypertrophy results from a pure increase in
muscle bulk, without fatty infiltration. This is a paradoxical response to
nerve injury and, although rare, it is associated with chronic nerve
irritation [9] (Figs.
13A,
13B,
13C,
14A,
14B,
14C,
15A,
15B).
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Fig. 13A. —47-year-old woman with longstanding brachial neuritis
(Parsonage-Turner syndrome). Longitudinal 5-12–MHz sonogram shows
increased echogenicity within atrophic right infraspinatus muscle
(arrows), caused by denervation.
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Fig. 13C. —47-year-old woman with longstanding brachial neuritis
(Parsonage-Turner syndrome). Sagittal oblique T1-weighted image (TR/TE,
500/14) of same shoulder as in B shows atrophy and fatty infiltration
of infraspinatus (I) as well as supraspinatus (S) muscles. Subscapularis (SU)
muscle bulk is normal.
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Fig. 14A. —60-year-old man with right calf pseudohypertrophy.
Longitudinal 5-12–MHz sonogram shows increased echogenicity within
gastrocnemius (arrows) and soleus muscles of right calf. Increased
muscular echogenicity and bulk, caused by fatty infiltration, confirms
pseudohypertrophy on sonography.
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Fig. 14C. —60-year-old man with right calf pseudohypertrophy. Axial
T1-weighted image (TR/TE, 500/14) shows enlargement and fatty replacement
within right soleus (S) and gastrocnemius (MG) muscles, compared with healthy
left side.
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Fig. 15A. —35-year-old man with true hypertrophy. Transverse
5-12–MHz sonogram of right calf shows enlargement of tibialis anterior
muscle (arrows), caused by chronic stimulation of deep peroneal
nerve. Normal echogenicity is maintained in hypertrophic muscle.
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Acknowledgments
We thank Barbara Taylor, Radiology Librarian, Royal Perth Hospital, for her
assistance in manuscript preparation.
References
- Fornage BD. Peripheral nerves of the extremities: imaging with
ultrasound. Radiology1988; 167:179
–182[Abstract/Free Full Text]
- Martinoli C, Bianchi S, Derchi LE. Tendon and nerve sonography.
Radiol Clin North Am 1999;37
: 691–711[Medline]
- Murphey MD, Smith WS, Smith SE, Kransdorf MJ, Temple HT. Imaging of
musculoskeletal neurogenic tumours: radiologic–pathologic correlation.
RadioGraphics1999; 19:1253
–1280[Abstract/Free Full Text]
- Martinoli C, Bianchi S, Gandolfo N. US of nerve entrapments in
osteofibrous tunnels of the upper and lower limbs.
RadioGraphics2000; 20:S199
–S217[Abstract/Free Full Text]
- Zanetti M, Strehle JK, Zollinger H, Hodler J. Morton neuroma and
fluid in the intermetatarsal bursae on MR images of 70 asymptomatic
volunteers. Radiology1997; 203:516
–520[Abstract/Free Full Text]
- Heilbrun ME, Tsuruda JS, Townsend JJ, Heilbrun MP. Intraneural
perineurioma of the common peroneal nerve: case report and review of the
literature. J Neurosurg2001; 94:811
–815[Medline]
- Duncan I, Sullivan P, Lomas F. Sonography in the diagnosis of
carpal tunnel syndrome. AJR1999; 173:681
–684[Abstract/Free Full Text]
- Jacobson JA, Jebson PJL, Jeffers AW, Fessell DP, Hayes CW. Ulnar
nerve dislocation and snapping triceps syndrome: diagnosis with dynamic
sonography—report of three cases. Radiology2001; 220:601
–605[Abstract/Free Full Text]
- Reimers CD, Schlotter B, Eicke BM, Witt TN. Calf enlargement in
neuromuscular diseases: a quantitative ultrasound study in 350 patients and
review of the literature. J Neurol Sci1996; 143:46
–56[Medline]
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Introduction
Focal Intrinsic Neural Lesions
