Intraneural nerve metastasis with multiple mononeuropathies.

Although cancer is a frequent condition, neoplastic involvement of the peripheral nervous system is rare. The mechanisms are heterogeneous and include lesions within the cerebrospinal fluid (CSF) space, local invasion (e.g. brachial plexus), compression, rarely direct infiltration, perineurial spread and even rarer intranerval metastasis. A 47-year-old woman had been treated for a carcinoid 10 years earlier and had received axillar irradiation. At presentation she suffered from weakness of the biceps brachii and was experiencing pain radiating from the axilla into the forearm and thumb. MR scans of the brachial plexus were negative and her symptoms were primarily considered to stem from a postradiation brachial plexopathy, Because of increasing pain, the brachial plexus was explored and a metastasis in the left musculocutaneous nerve was resected. Several months later, numbness and pain appeared in the ulnar nerve and another intrafascicular metastasis in the ulnar nerve was discovered. Resection with preservation of remaining fascicles was performed. This rare case report demonstrates that multiple mononeuropathies, resembling multiplex neuropathy, may be caused by intranerval metastasis.