Predicting recovery after fibular nerve injury: which electrodiagnostic features are most useful?

Objective: Although it is important to have strong predictors of outcome in peripheral mononeuropathies so that appropriate management can be instituted early, little is known about the prognostic value of electrodiagnostic results for these lesions. Our objective in this study was to evaluate the prognostic value of electrodiagnostic studies in fibular neuropathy.

Design: In this retrospective study, 39 of 138 subjects with fibular neuropathy met the inclusion criteria. Electrodiagnostic results at the time of testing were evaluated for their value in predicting outcome. Good outcome was defined as grade 4 or higher strength on the Medical Research Council Scale in ankle dorsiflexion.

Results: Compound muscle action potential responses from extensor digitorum brevis and tibialis anterior predicted prognosis: 81% of subjects with any tibialis anterior response and 94% with any extensor digitorum brevis response had a good outcome vs. those with absent responses (46% and 52%, respectively). Importantly, there was still a high likelihood of good outcome with absent compound muscle action potential responses. Tibialis anterior compound muscle action potential gave additional prognostic information when extensor digitorum brevis response was absent. Recruitment in tibialis anterior was predictive in traumatic cases. All patients with nontraumatic compression had a good outcome.

Conclusions: We conclude that electrodiagnostic studies produce useful prognostic information in fibular neuropathy, particularly in traumatic cases.