Opsoclonus-myoclonus-ataxia syndrome (often referred to as OMAS or opsoclonus-myoclonus syndrome) is an autoimmune disorder of the nervous system characterized by new movements of the limbs and eyes, abnormal behaviors, sleep dysregulation, and difficulty talking. OMAS can be triggered by a viral infection or a tumor (neuroblastoma). Because it is sometimes caused by a tumor, OMAS is called a paraneoplastic syndrome.
Symptoms of OMAS include:
- Rapid, involuntary eye movements (opsoclonus)
- Brief, involuntary twitching of muscle (myoclonus)
- Loss of muscle control or coordination of movements (ataxia)
- Unbalanced walk (unsteady gait)
- Sleep disturbances (insomnia)
- Changes in behavior (irritability, rage, etc.)
- Speech difficulties (slurring, hard to understand, inability to speak)
- Decreased muscle tone
- Nausea or vomiting
OMAS may be caused by an immune reaction to a tumor called neuroblastoma or an immune reaction to a viral illness. The immune reaction causes the body to produce antibodies to the cerebellum, which is located in the back of the brain. The impact on the cerebellum causes the patient to develop difficulty walking, chaotic eye movements, and a loss of developmental skills.
To confirm an OMAS diagnosis, your child will have several tests to look for brain abnormalities and to look for a tumors in the body. A lumbar puncture is often performed to look for evidence of an immune response. Urine tests, including vanillylmandelic acid (VMA) and homovanillic acid (HVA) tests are performed to look for evidence of a tumor. Extra tests, such as a metaiodobenzylguanidine (MIBG) scan, which involves injecting a small amount of radioactive material, are sometimes needed to look for a tumor.
Treatment for OMAS involves removal and treatment of a tumor, if one is found. Oftentimes, the immune system needs to be reset with medications, like steroids, intravenous immunoglobulin, or rituximab, a type of antibody therapy used to treat certain autoimmune diseases.
Opsoclonus-myoclonus treatment will also typically involve physical and occupational therapy to speed recovery.
Children with OMAS may have some remaining difficulties with attention, thinking and coordination. Early treatment offers the best chance at a full recovery.
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