Opsoclonus-myoclonus syndrome (OMS), also known as opsoclonus-myoclonus-ataxia syndrome, is a rare disorder characterized by opsoclonus (rapid, involuntary, chaotic, and conjugate eye movements or "dancing eyes"), myoclonic jerks, and ataxia. While it can be seen in any age group, it is more commonly described in the pediatric population. In children, onset is typically before 5 years of age. In addition to motor symptoms, children also often present with developmental regression, irritability, and sleep disturbances.

OMS may be autoimmune, postinfectious, postvaccination, or paraneoplastic in etiology. In adults, OMS can be associated with breast cancer or small cell lung carcinoma. In children, nearly half of those diagnosed with OMS are found to have an occult neuroblastoma. In children with OMS without an associated neuroblastoma, the cause is often not identified.

Disease onset tends to be subacute. In children, the course is often relapsing. The majority of affected children have long-term sequelae, including motor, behavioral, and cognitive deficits. Most adults achieve complete remission with therapy of the underlying cause.