Neuropathologic findings in idiopathic opsoclonus and myoclonus. Their similarity to those in paraneoplastic cerebellar cortical degeneration.

The neuropathologic findings in an idiopathic case of the opsoclonus/myoclonus syndrome are reported. Although neurologic dysfunction may have been more widespread, structural lesions were limited to the cerebellum and inferior olives. Severe depletion of Purkinje cells with preservation of granular cells was evident throughout the neo- and paleocerebellum; however, groups of Purkinje cells were preserved in the archicerebellum. No abnormalities were evident in the paramedian pontine reticular formation of the caudal pons. Inflammation and evidence of anoxic damage were absent. These changes are very similar to those described in paraneoplastic cerebellar cortical degeneration.