[Compression of the common peroneal nerve by a synovial cyst]

The authors report a successfully treated case of compression of the peroneal nerve by a simple (extraneural) ganglion. A brief review of the pathogenesis of intraneural and extraneural ganglions is exposed. The authors emphasize on considering this diagnosis in every patient who is complaining of pain or paralysis in the territory of the peroneal nerve. The treatment is always surgical. Prognosis depends on early diagnosis, non mutilating surgery for the nerve and ligation of an eventual stalk joining the ganglion to the articulation.