Preoperative evaluation of peripheral nerve injuries: What is the place for ultrasound?

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The purpose of this study was to evaluate the usefulness of ultrasound in the preoperative workup of peripheral nerve lesions and illustrate how nerve ultrasonography can be integrated in routine clinical and neurophysiological evaluation and in the management of focal peripheral nerve injuries. The diagnostic role and therapeutic implications of ultrasonography for different neuropathies are described.


The authors analyzed the use of ultrasound in 119 entrapment, tumoral, posttraumatic, or postsurgical nerve injuries of limbs evaluated in 108 patients during 2013 and 2014. All patients were candidates for surgery, and in all cases the evaluation included clinical examination, electrodiagnostic studies (nerve conduction study and electromyography), and ultrasound nerve study.

Ultrasound was used to explore the nerve fascicular echotexture, continuity, and surrounding tissues. The maximum cross-sectional area (CSA) and the presence of epineurial hyperechogenicity or intraneural hyper- or hypoechogenicity, of anatomical anomalies, dynamic nerve dislocations, or compressions were recorded.

The concordance rate of neurophysiological and ultrasonographic data was analyzed, classifying ultrasound findings as confirming, contributive, or nonconfirming with respect to electrodiagnostic data. The correlation between maximum nerve CSA and neurophysiological severity degree in entrapment syndromes was statistically analyzed.


Ultrasonography confirmed electrodiagnostic findings in 36.1% of cases and showed a contributive role in the diagnosis and surgical planning in 53.8% of all cases; the findings were negative (“nonconfirming”) in only 10.1% of the patients. In 16% of cases, ultrasound was not only contributive, but had a key diagnostic role in the presence of doubtful electrodiagnostic findings. The contributive role differed according to etiology, being higher for tumors (100%) and for posttraumatic or postsurgical neuropathies (72.2%) than for entrapment neuropathies (43.8%).


Ultrasound is a powerful, noninvasive tool for the examination of peripheral nerve injuries, and can guide diagnosis of and surgical strategy for focal peripheral nerve injuries. It allows direct visualization of the cause and extent of nerve lesions and finds its place between electrodiagnostic tests and exploratory surgery. It can provide invaluable information, such as the presence and extent of a mass, scar compression, or neuromas. The authors recommend it as a complement to routine clinical and neurophysiological evaluation and as the first-line imaging modality for masses of suspected nerve origin.

ABBREVIATIONSCMAP = compound muscle action potential; CSA = cross-sectional area; EMG = electromyography; LSD = least significant difference; MUAP = motor unit action potential; SNAP = sensory nerve action potential.

Article Information

INCLUDE WHEN CITING Published online January 22, 2016; DOI: 10.3171/2015.6.JNS151001.

Drs. Toia and A. Gagliardo contributed equally to this work.

Correspondence Andrea Gagliardo, “Clinical Course” Neurophysiology Unit, via A. De Gasperi, 81, Palermo 90146, Italy. email:

© AANS, except where prohibited by US copyright law.



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    Ultrasound axial scan of the median nerve at the wrist, showing 2 anatomical variants associated with carpal tunnel syndrome. Upper: Bifid median nerve in axial scan at the wrist. The nerve is divided by a fibrous hyperechoic septum (asterisk) into 2 compartments (arrows). Lower: A persistent median artery (A) can be found within this septum.

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    A: Ultrasound axial scan of the Guyon canal at the wrist. The ulnar nerve is generally located between the pisiform bone and the ulnar artery. In this case, ultrasound revealed a ganglion cyst (asterisk) occupying the canal and causing nerve compression. B: Intraoperative photograph obtained after nerve exposure and decompression but before removal of the ganglion cyst. C: Intraoperative photograph showing the cyst. The presence of the cyst was known beforehand and the risk of missing it was avoided. Figure is available in color online only.

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    Ultrasound scans of the forearm showing the typical shape of a neuroma in longitudinal (upper) and axial (lower) views of the median nerve. The axial scan shows a partial neurotmesis of the nerve with preservation of a significant percentage of nerve fascicles (arrow) in continuity below the neuroma. Figure is available in color online only.

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    Longitudinal ultrasound scans of the median nerve. Note the interruption of many fascicles (white arrows) for the presence of a neuroma (asterisk). Slightly moving the probe, different planes of the nerve can be explored and a small number of fascicles (black arrows) show their continuity across the lesion. These are the advantages of a dynamic real-time high-resolution ultrasound examination.

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    Ulnar nerve (arrows) in longitudinal ultrasound scan at the elbow. After a displaced fracture of the elbow, the patient did not recover any motor or sensory ulnar function. Ultrasound showed deposits of bone (asterisk) over the nerve fascicles, as a “fatal embrace” with the ulnar nerve. Note the shadow cone of the ultrasound that does not pass through the bone and obscures the underlying nerve.

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    Ultrasound axial scan of the posterior interosseus nerve (N) between the superficial and deep heads of the supinator muscle (S) in a patient who had suffered a hunting accident. The nerve has a focal huge increase of its CSA. A small hyperechoic metallic bullet (asterisk), easy to identify because of the prominent ultrasound artifact that it generates (arrows), pushes laterally and compresses the nerve, causing a deficit of the finger extension. The bullet is located on the superficial profile of the cortical bone of the radius (R). With an exact preoperative diagnosis surgery can be targeted without the need for wide exploration and dissection.

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    Superior trunk brachial plexopathy. Ventral branches of the C-5 (upper arrow), C-6 (middle arrow), and C-7 (lower arrow) spinal nerves in the interscalenic area. Note that the superior trunk shows an inner hyperechogenicity (white asterisk) and is surrounded by a thick hyperechoic fibrous tissue (black asterisk). This pattern suggests a stretching injury of the nerve trunk. Figure is available in color online only.

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    Upper: Schwannoma of the median nerve at the mid-arm in a longitudinal ultrasound scan. Following the median nerve by ultrasound, from the distal carpal tunnel to the axilla, we clearly show a mass, which originates from within this nerve and which displaces and does not infiltrate most of nerve fascicles. Lower: Intraoperative photograph showing the lesion. The diagnosis of schwannoma was confirmed by surgical exploration and histological examination. This case beautifully illustrates how close the ultrasound image is to reality. In this particular case, already conscious of the diagnosis and knowing that the nerve conduction and continuity are intact, thanks to the unparalleled high-resolution details, ultrasound imaging allowed for improvements in patient information, surgical planning, and decision making. Figure is available in color online only.

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    A–D: Axial ultrasound images showing the same schwannoma as in Fig. 8. Schwannomas usually displace most axon fibers, which can be spared during tumor enucleation. In axial live scans, the fascicles surrounding the tumor could be followed along the nerve (arrows) (also see Video 1).

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    Same schwannoma as in Figs. 8 and 9 in an axial and color Doppler ultrasound scan, which shows tumor neovascularization. The feeding artery, the plexiform veins, and eventual hypervascularity can be visualized with this technique. Figure is available in color online only.

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    Role of ultrasound with respect to neurophysiological examination in diagnosis and surgical planning in the 3 different groups of peripheral neuropathies. post-traum/post-surg = posttraumatic/postsurgical.



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