The remote effects of cancer on the nervous system.

Paraneoplastic syndromes are heterogeneous in their clinical presentations and their associations with particular tumor types and are an important part of the differential diagnosis of neurologic dysfunction in patients with or without a known neoplasm. Patients presenting with one of the more distinctive syndromes, such as subacute cerebellar degeneration, opsoclonus-myoclonus, and the Lambert-Eaton syndrome, should undergo a careful evaluation for the presence of an occult malignancy. The importance of looking for a monoclonal gammopathy in patients with certain polyneuropathies and motor neuron syndromes is also becoming clear. At this time, an autoimmune pathogenesis has been clearly demonstrated only for the Lambert-Eaton syndrome. Specific autoantibodies in other syndromes appear to be valuable diagnostic markers for the presence of an underlying malignancy, but the actual role of these antibodies in producing tissue damage and clinical disease is still unknown.