HIGH SCIATIC LESION MIMICKING PERONEAL NEUROPATHY AT THE FIBULAR HEAD

We report 4 patients with severe, axon-loss, high sciatic mononeuropat hies affecting exclusively the peroneal fibers: a boy with a slowly-gr owing nerve tumor, a woman with an injection injury, and 2 patients wh o had undergone proximal femur surgery. Clinically, the findings mimic ked those seen with common peroneal neuropathy at the fibular head. Th e peroneal conduction studies were very low in amplitude/unelicitable. Conversely, the tibial studies and H-responses were normal in all; th e sural responses were normal in one while low in amplitude/unelicitab le in the remaining three. The biceps femoris, short-head, and all per oneal-innervated muscles showed fibrillations and profound motor unit loss. Conversely, the remaining hamstrings and all tibial-innervated m uscles were normal. We conclude that a sciatic lesion can imitate a mo re distal peroneal lesion. Needle EMG of the biceps femoris, short hea d, is essential for correct diagnosis.