Opsoclonus-myoclonus syndrome (OMS) is a rare autoimmune condition that usually affects young children.
Most children with OMS are diagnosed at around 18 months of age.
It affects one out of every 5 million children worldwide, and is slightly more common in girls than boys.
In OMS, a neuroblastoma) or a viral infection triggers the immune system to attack the nervous system.
The symptoms of OMS usually begin abruptly and can include rapid, repeated eye movements (opsoclonus) jerking movements (myoclonus), and loss of balance (ataxia).
OMS may be initially diagnosed as acute cerebellar ataxia.
Most patients with OMS improve with immunotherapy treatment, though the relapse rate in children is 50 to 75 percent.
Aggressive, early treatment appears to lower the rate of relapse and improve outcomes.
Opsoclonus-myoclonus syndrome symptoms include rapid, repeated eye movements (opsoclonus) and repeated, brief muscle jerks in the arms and legs (myoclonus).
Other symptoms may include: loss of balance with inability to sit, stand, or walk, hand tremors, difficulty with speech sleep problems, specifically insomnia, behavioral problems such as irritability and rage attacks, reduced muscle tone, and vomiting.
In some cases, speech and language may be completely lost.
Symptoms of OMS often start abruptly and can become chronic.
In young children, the cause of OMS in 50 to 80 percent of cases is a small, benign neuroblastoma or a ganglioneuroblastoma.
The tumor is usually located in the chest or abdomen and is thought to cause the immune system to attack the nervous system.
The remainder of cases is unknown (idiopathic) or may be caused by tumors that have regressed.
Viral infections may also be the cause, especially in older children and teens.
OMS in adults is most often caused by lung or breast cancer.
Standard immunotherapy treatment for OMS is started soon after diagnosis and usually continues for at least one to two years.
The goal of treatment is a decrease or remission of symptoms.
A combination of immunotherapies includes a high dose of corticosteroids, intravenous immunoglobulin (IVIg), and rituximab for moderate to severe cases.