Six patients, aged 10 to 27 years, with insidiously progressive, painless weakness in the distribution of a single major lower extremity nerve are reported from the University of California, San Francisco. The duration at diagnosis varied from 3 months to 8 years. The sciatic nerve was involved in three patients, the common peroneal in two, and the femoral nerve in one. The appearance of the nerve at surgery was normal in two, atrophied in two, and fibrosed in one. EMG revealed a chronic axonal mononeuropathy without conduction block or focal conduction slowing. MRI, CT, and US imaging failed to reveal a nerve mass or compression. 
COMMENT. The authors ask the question: Could the patients have had a nerve tumor not uncovered by standard MRI or surgery and too proximal for localization by nerve conduction studies? The diagnosis of neurofibromatosis type 2 was confirmed by a gadolinium MRI in a 14-year-old girl who presented with flaccid weakness and wasting of the left upper limb and EMG evidence of brachial plexopathy . The standard MRI was inconclusive whereas the gadolinium imaging revealed enlargement of neural formina C 5-6 on the left side and evidence of a plexiform neurofibroma. Examination of the skin showed depigmented and cafe-au-lait patches, helpful in the diagnosis in this case.