Opsoclonus-myoclonus syndrome (OMS) is a rare disorder that affects the nervous system. Symptoms include rapid, multi-directional eye movements (opsoclonus), quick, involuntary muscle jerks (myoclonus), uncoordinated movement (ataxia), irritability, and sleep disturbance. The onset of OMS is usually abrupt and often severe. The disease may become chronic. OMS typically occurs in association with tumors (neuroblastomas), or following a viral or bacterial infection. Treatment may include corticosteroids or ACTH (adrenocorticotropic hormone). When there is a tumor present, treatment may include chemotherapy, surgery, and/or radiation. In some cases, when the underlying cause of OMS is treated, symptoms improve.

Opsoclonus-myoclonus syndrome is often associated with the presence of a tumor (such as neuroblastoma) and referred to as a paraneoplastic syndrome. In other cases, it is associated with a viral infection (such as influenza, Epstein-Barr, hepatitis C, HIV,or Coxsackie B) or a bacterial infection (such as as streptococcal, Lyme disease, or mycoplasma). In some cases, the cause is unknown.

Signs and symptoms of opsoclonus-myoclonus syndrome (OMS) may include:

• Unsteady, trembling gait (manner of walking)
• Sudden, brief, shock-like muscle spasms (myoclonus). While it occurs most when trying to move and worsens with agitation or stimulation, it can also be present at rest. Myoclonus can make a person appear nervous or shaky, or have jerking movements. The face, eyelids, limbs, fingers, head and trunk may be involved. When the illness is at its worst, sitting or standing is difficult or impossible.
• Irregular, rapid eye movements (opsoclonus)

Other symptoms may include difficulty speaking or inability to speak, difficulty eating or sleeping, excessive drooling, lack of coordination, rage attacks, head tilt, a decrease in muscle tone, and/or general feeling of discomfort or illness.

Children may appear to be nervous, irritable, or lethargic while adults may have mental clouding (encephalopathy).

There are no official treatment recommendations for OMS. Management may involve: 

• Surgery, chemotherapy, and/or radiation: When there is a tumor present, treatment such as surgery for tumor removal, chemotherapy, or radiation may be required. In children, the removal of the neuroblastoma does not always improve neurologic symptoms. Some adults with paraneoplastic OMA do not have more neurologic symptoms with the removal pf the neuroblastoma or after its treatment.
• Corticosteroids or ACTH (adrenocorticotrophic hormone), human intravenous immunoglobulins (IVIG), or immunosuppressive agents such as immuran, cyclophosphamide, mycophenolate mofetil, and rituximab. In many cases, a combination of medications leads to the best result. Adults may be less likely to respond to immunological treatment compared with children.
• Trazodone: Used to treat sleep problems and associated rage attacks.

Although a person may fully recover from the underlying cause of OMS, many people continue to have some neurological impairment. Full recovery is more common in cases due to infection than those due to neuroblastoma. Children with the mildest symptoms have the greatest chance of returning to normal after treatment. For those with moderate severity, myoclonus tends to lessen over time, but coordination may not fully return. Some learning and behavioral issues may also remain. Those with severe symptoms have the highest risk for permanent neurological problems. 

Relapses of neurological symptoms may occur with future illness, fever, stress, medication, anesthesia, discontinuation of immunotherapy, or after immunizations. These relapses are common and may occur more than once. In some cases, many years may pass between episodes. Relapses should be treated, preferably with the same type of treatment used initially. 

A diagnosis of OMS is mostly based on the presence of the characteristic signs and symptoms. In some cases, laboratory tests for certain antibodies and/or for abnormal white blood cells may also be done.

The diagnosis is based on the presence of any 3 out of the 4 following criteria:

1. Rare type of cancer that affects the nerve tissue (neuroblastoma)
2. Uncontrolled eye movement (opsoclonus)
3. A movement disorder with sudden muscle contractions (myoclonus) and/or lack of coordination (ataxia)
4. Behavioral and/or sleep disturbance

In adults with OMS, a blood exam may show Hu anti-neuronal nuclear antibodies (anti-Hu) but not in children. The most efficient methods for detecting a neuroblastoma (which is present in many affected people) are MRI with contrast and helical (or spiral) CT scanning.

Opsoclonus-myoclonus syndrome does not appear to be inherited. The disorder is sporadic and occurs in people with no family history of the condition.