Neuromuscular complications of systemic cancer.

In patients with cancer, neuromuscular dysfunction often develops as a result of some combination of direct effects of the cancer, from complications of therapy, or from paraneoplastic syndromes. Direct effects include leptomeningeal involvement by tumors (most frequently of the breast and lung) causing polyradiculopathy and compressive brachial and lumbar plexopathies that produce distinctive and typically painful syndromes. The differentiation between radiation and tumor-associated brachial plexopathies may be difficult, however. Peripheral neuropathy is an important dose-limiting toxic side effect of two commonly utilized agents, vincristine and cisplatin. Recent studies have suggested that this complication may be ameliorated or even prevented by prophylactic administration of protective agents. Finally, cancer can cause neuromuscular dysfunction through more remote effects and can produce a variety of paraneoplastic syndromes that include subacute sensory neuropathy. Lambert-Eaton myasthenic syndrome, and the neuropathy associated with paraproteinemia. In some syndromes, the presence of specific antibodies that cross-react with both neuromuscular tissues and primary tumors strongly suggests an immune-mediated pathogenesis. In some patients, immunosuppressive therapies and plasmapheresis may relieve symptoms.