Nerve ultrasound and 3D-MR neurography suggestive of intraneural perineurioma.

An 8-year-old girl presented with progressive painless right peroneal and tibial nerve palsy. A 20-year-old woman had insidious weakness of the left wrist and fingers extension. Both underwent neurophysiology (tables e-1 through e-4 on the Neurology® Web site at Neurology.org) and nerve ultrasound that showed enlargement of sciatic (figure, A) and radial nerve (figure, D–E). A 3D–magnetic resonance (MR) neurography examination detected a 20-cm-long uniform enlargement of sciatic nerve (figure, B) and a 6-cm-long fusiform enlargement of radial nerve (figure, F) with mild hyperintensity and marked contrast enhancement, suggesting intraneural perineurioma. Both had surgical exploration but not biopsy: the macroscopic and imaging appearance (figure, C), texture, and clinical history (young age, progressive motor symptoms) strongly suggested the diagnosis intraoperatively. Intraneural perineurioma is a rare benign nerve tumor presenting in youth. MR neurography aids the diagnosis, possibly avoiding nerve biopsy when there are typical MR features.