Electrodiagnostic findings and surgical outcome in isolated first branch lateral plantar neuropathy: a case series with literature review.

Abstract

Two patients with recalcitrant unilateral heel pain and plantar fasciitis were referred for electrodiagnostic evaluation. They both reported constant, sharp, unilateral medial heel pain, with nocturnal symptoms, as well as exacerbation by weight-bearing activities. Examination of both patients demonstrated focal medial heel tenderness and a Tinel sign over the tarsal tunnel on the affected side. Neither patient had weakness or sensory deficits in the affected foot. In both patients, findings on nerve conduction studies were normal in the affected foot, including the first branch of the lateral plantar nerve (FBLPN), as well as the medial and lateral plantar motor and sensory (ie, mixed nerve) responses. Needle electromyographic (EMG) abnormalities were found only in the abductor digiti quinti pedis (ADQP), an intrinsic foot muscle that is exclusively innervated by the FBLPN, but there were no EMG abnormalities noted in the medial or lateral plantar-innervated muscles studied, nor the contralateral ADQP. Both patients then underwent surgical decompression of the FBLPN. Postoperative follow-up (patient 1 at 10 months, patient 2 at 21 months) revealed excellent outcomes, as defined by symptom resolution, in both patients. Electrodiagnostic evaluation was useful in diagnosing isolated first branch lateral plantar neuropathy.