Paraneoplastic opsoclonus-myoclonus. Association with medullary thyroid carcinoma and review of the literature.

The syndrome of opsoclonus-myoclonus (OM) is an infrequent but well-known "remote effect" of neuroblastoma in children. The OM syndrome is even less frequent in adults. A few cases of adult paraneoplastic OM have been described in association with several systemic neoplasms. We report the unique case of a 29-year-old man with metastatic medullary thyroid carcinoma in whom OM developed as part of a generalized transient encephalopathy. We outline the postulated anatomic lesions and pathophysiologic mechanisms underlying the OM syndrome, as well as examine the possible connections between the neuroendocrine derivation of medullary thyroid carcinoma and the neurotoxic and/or autoimmune theories of the causation of the OM syndrome in patients with systemic neoplasms.