A Unique Case of Common Peroneal Nerve Entrapment.

The authors present a case of a previously healthy 36-year-old man with a 3-day history of spontaneous complete right lower extremity foot drop. He noticed the symptoms immediately when he attempted to stand after waking from sleep. The patient had no history of similar symptoms, recent trauma, or peripheral nerve disease. Physical examination showed a slap foot gait, complete numbness of the lateral leg and dorsal foot, and 0/5 strength with ankle and great toe dorsiflexion and ankle eversion. Serum laboratory studies showed normal values. Nerve conduction studies confirmed increased latency and decreased amplitude of the right peroneal nerve at the knee, whereas electromyography showed denervation of the tibialis anterior and extensor digitorum brevis. Anteroposterior and lateral radiographs showed a normal right knee with the exception of a posterior fibular neck exostosis. Physical therapy, an ankle-foot orthosis, and a 5-day course of oral prednisone burst (50 mg) were prescribed. After 1 month of therapy without resolution, the patient underwent surgical release of the common peroneal nerve and excision of the bony prominence. Twelve days postoperatively, the patient had no sensory improvements but had improved findings on motor examination. Three months postoperatively, the patient had near-normal sensation to light touch in the superficial and deep peroneal nerves, with 5/5 strength and a normal gait. The patient returned to all activity without limitations. The authors present this unique case describing a fibro-osseous source of common peroneal compressive neuropathy and review the literature for spontaneous peroneal entrapment, highlighting the importance of prompt diagnosis and treatment.