Opsoclonus, myoclonus, ataxia, and encephalopathy in adults with cancer: a distinct paraneoplastic syndrome.

The clinical and pathological findings in 4 adults with cancer and opsoclonus were compared with those of 15 other patients described elsewhere. The clinical syndrome of paraneoplastic opsoclonus is characterized by the acute onset of opsoclonus and truncal ataxia, often accompanied by encephalopathy, myoclonus and a cerebrospinal fluid pleocytosis. Unlike most other paraneoplastic syndromes, the course is often remitting and relapsing. Neuropathological examination in 3 of our patients showed lymphocytic cuffing of occasional blood vessels throughout the central nervous system, associated with a mild, diffuse proliferation of microglia in 1 patient. Apart from a mild, patchy loss of Purkinje cells in 1 patient, there was no loss of neurons from the cerebellum, brainstem, cerebral hemispheres, or spinal cord. These patients differ from those with the more common paraneoplastic cerebellar degeneration by the predominance of truncal over limb ataxia, the presence of myoclonus, the absence of severe dysarthria, a tendency for remission, and the preservation of Purkinje cells.