Intraneural nerve metastasis with multiple mononeuropathies

Although cancer is a frequent condition, neoplastic involvement of the peri pheral nervous system is rare. The mechanisms are heterogeneous and include lesions within the cerebrospinal fluid (CSF) space, local invasion (e.g. b rachial plexus), compression, rarely direct infiltration, perineurial sprea d and even rarer intranerval metastasis. A 47-year-old woman had been treat ed for a carcinoid 10 years earlier and had received axillar irradiation. A t presentation she suffered from weakness of the biceps brachii and was exp eriencing pain radiating from the axilla into the forearm and thumb. MR sca ns of the brachial plexus were negative and her symptoms were primarily con sidered to stem from a postradiation brachial plexopathy. Because of increa sing pain, the brachial plexus was explored and a metastasis in the left mu sculocutaneous nerve was resected. Several months later, numbness and pain appeared in the ulnar nerve and another in intrafascicular metastasis in th e ulnar nerve was discovered. Resection with preservation of remaining fasc icles was performed. This rare case report demonstrates that multiple monon europathies, resembling multiplex neuropathy, may be caused by intranerval metastasis.