Paraneoplastic opsoclonus: a neuropathologic study of two cases.

The association of opsoclonus and malignant neoplasia is infrequent. The clinical and neuropathological data of two patients in whom opsoclonus and ataxia developed 7 and 11 months before the detection of a bronchial carcinoma are reported. Loss of Purkinje cells, edema of dentate nucleus and peridental demyelination were the most important neuropathological findings; neither carcinomatous metastases nor inflammatory signs were found in the brain. From the review of the pathological reports of paraneoplastic opsoclonus, the following conclusions can be drawn: the changes in the cerebellum are produced by the paraneoplastic cerebellar degeneration and are unrelated to the origin of opsoclonus, which has other anatomic substrates; paraneoplastic opsoclonus is a "remote effect" of cancer with an inflammatory basis, for which neurotoxic and immunological mechanisms have been hypothesized.