Opsoclonus myoclonus syndrome (OMS), also known as opsoclonus-myoclonus-ataxia (OMA), is a rare neurological disorder of unknown cause which appears to be the result of an autoimmune process involving the nervous system. It is an extremely rare condition, affecting as few as 1 in 10,000,000 people per year. It affects 2 to 3% of children with neuroblastoma and has been reported to occur with celiac disease and diseases of neurologic and autonomic dysfunction. Signs and symptoms Symptoms include: opsoclonus (rapid, involuntary, multivectorial (horizontal and vertical), unpredictable, conjugate fast eye movements without intersaccadic [quick rotation of the eyes] intervals) myoclonus (brief, involuntary twitching of a muscle or a group of muscles) cerebellar ataxia, both truncal and appendicular aphasia (a language disorder in which there is an impairment of speech and of comprehension of speech, caused by brain damage) mutism (a language disorder in which a person does not speak despite evidence of speech ability in the past, often part of a larger neurological or psychiatric disorder) lethargy irritability or malaise drooling strabismus (a condition in which the eyes are not properly aligned with each other) vomiting sleep disturbances emotional disturbances (including fits of rage) About half of all OMS cases occur in association with neuroblastoma (a cancer of the sympathetic nervous system usually occurring in infants and children). Disease course and clinical subtypes In most cases, OMS starts with an acute flare-up of physical symptoms within days or weeks, but some less obvious symptoms such as irritability and malaise may begin weeks or months earlier. Cause In children, most cases are associated with neuroblastoma and most of the others are suspected to be associated with a low-grade neuroblastoma that spontaneously regressed before detection. In adults, most cases are associated with breast carcinoma or small-cell lung carcinoma. It is one of the few paraneoplastic (meaning 'indirectly caused by cancer') syndromes that occurs in both children and adults, although the mechanism of immune dysfunction underlying the adult syndrome is probably quite different. It is hypothesized that a viral infection (perhaps St. Louis encephalitis, Chikungunya, Epstein-Barr, Coxsackie B, enterovirus, or just a flu) causes the remaining cases, though a direct connection has not been proven. Rare cases of Opsoclonus myoclonus syndrome associated with Lyme disease have also been reported. OMS is not generally considered an infectious disease. OMS is not passed on genetically. Diagnosis Because OMS is so rare and occurs at an average age