Opsoclonus

Opsoclonus is a rare disorder of the saccadic system, in which fixation is continuously interrupted by multivectorial, back-to-back saccades that at times can be seen only with an ophthalmoscope. To diagnose it reliably, eye movement recording is required. Opsoclonus may be a harbinger of an occult malignancy, though many cases are postinfectious, toxic-metabolic or idiopathic. The underlying malignancy is usually neural crest tumors in children and lung, breast, or gynecologic cancer in adults. Opsoclonus can be accompanied by myoclonus and ataxia. Concurrent appearance of oscillations affecting eyes and limbs suggests a common brainstem generator. Dysfunction of the glycinergic omnipause neurons in the nucleus raphe interpositus has been proposed. Autoantibodies against neural epitopes shared with a tumor are implicated in the pathogenesis of opsoclonus in paraneoplastic cases. Because of the association with malignancies, full oncological work-up is indicated in every case. Coexisting opsoclonus carries a relatively good prognosis for the cancer; however, the neurologic disability may remain even if the tumor has been arrested. New, potentially effective immunoadsorption therapy for opsoclonus is currently under investigation.