AssessmentsOpsoclonus myoclonus syndrome (NORD)
USMLE® Step 1 style questions USMLE
An 18-month-old boy is brought to the office by his parent due to abnormal body movements. His parent states that the patient has been walking abnormally for the past several weeks with frequent falls. The patient’s temperature is 37.0°C (98.6°F), pulse is 108/min, and blood pressure is 125/80 mmHg. Physical examination reveals multidirectional, nonrhythmic eye movements. The patient is also observed to have sporadic limb jerkings and truncal ataxia when walking. A left-sided immobile abdominal mass is palpated. There is no hepatosplenomegaly. Laboratory testing reveals anemia, and elevated levels of homovanillic acid and vanillylmandelic acid are detected in the urine. The abdominal mass most likely originated from which of the following embryologic derivatives?
Content Reviewers:Rishi Desai, MD, MPH
Opsoclonus-myoclonus syndrome is also called OMS or dancing eyes-dancing feet syndrome.
Opsoclonus describes seemingly random, involuntary, and rapid eye movements in the horizontal, vertical, and diagonal directions.
Myoclonus describes lightening-like limb movements or limb jerks, that can also be more tremulous.
The syndrome also causes ataxia, which often results in the inability to walk, sit or crawl, and the loss of previously attained abilities, like speech.
The precise cause of OMS is unknown, but in children, it’s often due to a paraneoplastic syndrome.
The idea is that a hidden or occult tumor - like a neuroblastoma or ganglioneuroblastoma - triggers the body’s immune system, and the resulting antibodies unintentionally target healthy cells of the nervous system.
CD20+ B-cells that get into the CSF fluid seem to play an important role.
In older children and adolescents OMS is thought to be triggered by an infection, and in adults, it’s often due to a paraneoplastic process due to lung or breast cancer, for example.
In children with OMS, there’s almost always ataxia, so it’s sometimes referred to as OMAS - with the A representing ataxia.
In fact, most toddlers with OMS are initially misdiagnosed with acute cerebellar ataxia of childhood.
The diagnosis of OMS is also often based on symptoms like opsoclonus and myoclonus which can appear abruptly, progressing over days to weeks.
Opsoclonus-myoclonus syndrome (OMS) is a rare condition, characterized by rapid, uncontrolled eye movements (opsoclonus) and sudden twitching or jerking of muscles (myoclonus). It can also present with ataxia, which often results in the inability to walk, sit or crawl, and the loss of previously attained abilities, like speech.
The cause of OMS is not well understood, but it is thought to be due to an autoimmune condition in which the body attacks the nervous system, resulting in characteristic signs and symptoms. Treatment involves immunosuppressive therapy like corticosteroids, intravenous immunoglobulin or IVIG, drugs like cyclophosphamide, and rituximab.