Rare Entrapment of the Deep Peroneal Nerve by a Ganglion Cyst at the Ankle.

Entrapment of the deep peroneal nerve (DPN) is an uncommon yet clinically significant cause of lateral ankle and dorsal foot pain. Among its rare etiologies, ganglion cysts are often overlooked during initial assessments. We present a case of a 56-year-old woman who reported a six-month history of progressive, electric shock-like pain on the dorsum of her left foot, accompanied by a firm mass on the anterolateral ankle. The pain became constant after three months. A physical exam showed a slightly mobile mass and a positive Tinel sign around the DPN. An MRI revealed a cystic lesion compressing the nerve, which led to prompt surgical excision. During the surgery, a hemorrhagic ganglion cyst compressing the DPN was discovered and excised, and nerve decompression was performed. While uncommon, ganglion cysts should be considered in the differential diagnosis for patients exhibiting focal nerve symptoms and soft tissue masses. Timely surgical intervention might help prevent chronic neuropathy and promote functional restoration.