Opsoclonus myoclonus is a syndrome in which the eyes dart involuntarily (opsoclonus or dancing eyes) and muscles throughout the body jerk or twitch involuntarily (myoclonus).
Opsoclonus myoclonus is a very rare syndrome that strikes previously normal infants, children, or adults, often occurring in conjunction with certain cancerous tumors, viral infections, or medication use. Onset can be very sudden and dramatic, with a quick progression.
Most children who develop opsoclonus myoclonus are under the age of two when they are diagnosed. Boys and girls are affected equally.
Causes and symptoms
Many cases of opsoclonus myoclonus follow a bout of a viral illness such as infection with influenza, Epstein-Barr or Coxsackie B viruses, or after St. Louis encephalitis. About half of all cases are associated with a cancerous tumor; this kind of symptom that occurs due to cancer is termed a paraneoplastic syndrome. In children, the most common type of tumor that precipitates opsoclonus myoclonus is called neuroblastoma. Neuroblastoma can cause tumors in the brain, abdomen, or pelvic area. The cancerous cells develop from primitive nerve cells called neural crest cells. When opsoclonus myoclonus occurs in adults, it is usually associated with tumors in the lung, breast, thymus, lymph system, ovaries, uterus, or bladder. Rarely, opsoclonus myoclonus can occur after the use of certain medications such as intravenous phenytoin or diazepam , or subsequent to an overdose of the antidepressant amitriptyline.
No one knows exactly why opsoclonus myoclonus occurs. It is postulated that the presence of a viral infection or tumor may kick off an immune system response. The immune system begins trying to produce cells that will fight the invaders, either viruses or cancer cells. However, the immune cells produced may accidentally also attack areas of the brain, producing the symptoms of opsoclonus myoclonus.
Patients with opsoclonus myoclonus all have both opsoclonus and myoclonus. They experience involuntary, rapid darting movements of their eyes, as well as lightning-quick jerking of the muscles in their faces, eyelids, arms, legs, hands, heads, and trunk. Many individuals with opsoclonus myoclonus also experience weak and floppy muscles and a tremor. The movement disorder symptoms are incapacitating enough to completely interfere with sitting or standing when they are at their most severe. Difficulties eating, sleeping, and speaking also occur. Other common symptoms include mood changes, rage, irritability, nervousness, anxiety, severe drowsiness, confusion, and decreased awareness and responsiveness.
Diagnosis is primarily arrived at through identification of concurrent opsoclonus and myoclonus. Laboratory testing of blood and spinal fluid may reveal the presence of certain immune cells that could be responsible for attacking parts of the nervous system, such as autoantibodies. When opsoclonus myoclonus is diagnosed, a search for a causative condition such as tumor should be undertaken.
The treatment team will include a neurologist and neurosurgeon. A physical therapist, occupational therapist, and speech and language therapist may help an individual with opsoclonus myoclonus retain or regain as much functioning as possible.
If opsoclonus myoclonus is due to the presence of a tumor, the first types of treatment will involve tumor removal and appropriate treatment of the cancer. Some adult cases of opsoclonus myoclonus resolve spontaneously, without specific treatment.
Treatment of the symptoms of opsoclonus myoclonus include clonzaepam or valproate. These may decrease the severity of both the opsoclonus and the myoclonus.
Other treatments for opsoclonus myoclonus include the administration of the pituitary hormone, called adrenocorticotropic hormone (ACTH). ACTH prompts the production of steroid hormones in the adrenal glands. When ACTH is given in high intravenous (IV) doses for about 20 weeks, the body produces large quantities of steroids, which can help quell any immune response that may be responsible for the opsoclonus myoclonus. Intravenous immunoglobulin treatment (IVIG), Azathioprine, and intravenous steroid treatments may also be given in an effort to suppress the immune system's response.
Two treatments that filter the blood in an effort to remove potentially damaging immune cells may also be attempted, although they are generally only able to be performed on adults. These include therapeutic apheresis and immunoadsorption. In these procedures, the patient's blood or plasma is processed to extract certain immune cells; the blood or plasma is then returned to the patient. These procedures may need to be repeated five or six times, but improvement is often rapid and may last up to two to three months.
The prognosis for opsoclonus myoclonus is varied. The milder the case prior to treatment, the more likely full recovery may occur. When opsoclonus myoclonus is due to a viral illness, there is a higher possibility for resolution of symptoms than when the condition results from neuroblastoma. Furthermore, although the degree of myoclonus may decrease, there are still often some residual coordination problems, difficulties with learning, behavior and/or attention, and obsessive-compulsive disorder. Children with very severe cases of opsoclonus myoclonus are likely to continue to have severe problems, and will probably never have normal intelligence or the ability to live independently.
Many children have flares of their symptoms or actual relapses of the disease when they suffer from viral illnesses, even years later. The treatments for such relapses are the same as for the initial illness.
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Opsoclonus-Myoclonus USA and International. SIU School of Medicine, 751 North Rutledge, Suite 3100, Springfield, IL 62702. (217) 545-7635; Fax: (217) 545-1903. [email protected] <http://www.omsusa.org/index.htm>.
Rosalyn Carson-DeWitt, MD