An Unusual Cause of Foot Drop: Peroneal Extraneural Ganglion Cyst.

Peripheral neuropathies caused by ganglion cysts are quite rare, especially in the lower extremities. The case of a 64-year-old male with a 2-day history of foot drop and tenderness in the region of the left fibular neck is presented. Physical examination and electromyogram findings verified peroneal nerve palsy. Ultrasonography showed cystic mass localized proximal of the peroneal muscle structures. Magnetic resonance imaging revealed a cystic-appearing mass around the fibular neck that compressed the common peroneal nerve. Surgical excision and ligation of the cyst pedicle were performed. The pathology reports confirmed the diagnosis of a ganglion cyst. The patient regained full function within two months of the surgery. Early sensory symptoms before foot drop should be considered as an indication of surgical excision to prevent delayed damage. Ligation or electrocoagulation of the cyst pedicle should be a part of surgical procedure to avoid recurrences.