Radial nerve palsy owing to localized hypertrophic neuropathy (intraneural perineurioma) in early childhood.

Localized hypertrophic neuropathy, also termed intraneural perineurioma, is a rare disorder of unknown etiology that produces a slowly progressive painless focal lesion of a peripheral nerve. It is characterized histologically by concentric whorls ("onion bulbs") of epithelial membrane antigen-reactive, S-100 protein-negative perineurial cells surrounding nerve fibers. We report a radial nerve palsy in a child aged 2 years in whom the diagnosis of localized hypertrophic neuropathy was made by biopsy. Resection of the affected nerve segment and sural nerve grafting produced no useful recovery after 3 years, probably because of the long duration of denervation. When this mononeuropathy presents in early childhood, uncertainty over the time of onset can lead to difficulty in distinguishing this potentially treatable lesion from congenital and other causes of nerve palsy.