Signs, symptoms, and significance of paraneoplastic neurological syndromes.

Neurological lesions attributed to the remote effect of cancer on the nervous system are protean, involving any part of the central and/or peripheral nervous system including the muscles. These paraneoplastic neurological syndromes are relatively uncommon in cancer patients, their relative frequency is variable, and their pathogenesis remains largely unknown. All forms of PNNS have been seen both in patients with and without cancer, and, unlike the paraneoplastic endocrinopathies, tumor removal is not necessarily followed by the remission of PNNS. For some PNNS, specific pathogenic mechanisms have been established or are highly probable. Thus, certain metabolic encephalopathies or the carcinoid myopathy are due to production of hormones or hormonelike substances by the tumor. The discovery of the most "typical" forms of PNNS justifies a careful search for an underlying neoplasia.