Which electrodiagnostic test findings suggest deep peroneal nerve entrapment?

Updated: Oct 15, 2019
  • Author: Minoo Hadjari Hollis, MD; Chief Editor: Thomas M DeBerardino, MD  more...
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Answer

Needle examination may reveal the presence of fibrillations and positive sharp waves in the extensor digitorum brevis only if entrapment is present at the anterior tarsal tunnel. If entrapment is present more proximally, the denervation is present in the anterior tibial muscle as well as in the extensor digitorum brevis.

Denervation may, however, be present with other neurologic conditions. The short head of the biceps femoris, as well as the medial gastrocnemius, the tensor fasciae latae, and the lumbar paraspinal muscles, should be tested if findings in the deep peroneal muscles rule out a more proximal problem (eg, a radiculopathy). The absence of findings in these muscles, as well as in the peroneus longus and peroneus brevis, confirms the presence of a deep peroneal motor-nerve injury.

Some reports stated that there may be a high percentage of denervation in the foot intrinsic muscles in healthy subjects, but subsequent reports found that the actual percentage of abnormal findings in healthy subjects is low for a well-trained electromyographer. In many cases, electrodiagnostic test findings are normal because these dynamic syndromes frequently improve or resolve at rest.


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