Common peroneal nerve compression by a popliteal venous aneurysm.

A 58-yr-old man with a right foot drop and a sensory change in the right calf and foot, which developed after a bladder operation, was referred to our clinic for an electrodiagnostic evaluation. Neurologic examination showed grade 1 weakness of the right ankle in dorsiflexion, great toe in dorsiflexion, and ankle in eversion. In addition, the patient complained of pain and a tingling sensation in the right calf and foot. Electrodiagnostic findings were consistent with right common peroneal nerve palsy at the level of the fibula head. In addition, duplex ultrasonography, computed tomography angiography, and magnetic resonance imaging revealed a right popliteal venous aneurysm and impingement of the right common peroneal nerve between the aneurysm and the belly of the biceps femoris muscle. After resection of the aneurysm, his sensory symptoms and motor strength of the right foot and calf gradually improved. This case suggests that compression by the venous system should be considered when there is clinical evidence of focal neuropathy but no abnormal findings at common entrapment sites.