Terminal sensory branches of the superficial peroneal nerve: an entrapment syndrome.

This report describes an entrapment syndrome of the superficial peroneal nerve terminal sensory branches. Two patients presented with numbness and tingling of the foot dorsum. These symptoms increased with activity such as walking, running, and squatting. The signs were 1) a decrease in sensation to light touch and pin prick on the foot dorsum over the cutaneous distribution of the nerve with sparing of the first web space; 2) a soft tissue bulge over the anterolateral aspect of the leg approximately 10 cm above the lateral malleolus; 3) a Tinel sign over the bulge; 4) an increase in the size of the bulge either with resisted ankle dorsiflexion or weight bearing; and 5) tenderness over the bulge or distally over the terminal sensory branches of the superficial peroneal nerve. Electrodiagnostic studies revealed an unrecordable evoked response or a prolonged distal latency of the terminal sensory branches of the superficial peroneal nerve. Treatment consisted of surgical decompression of the nerve at the bulge by fasciotomy. Patients responded with complete symptomatic relief. To provide accurate treatment, the diagnosis of entrapment syndrome of the superficial peroneal nerve terminal sensory branches must be differentiated from other causes of pain and numbness in the ankle area.