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 antidepressantamitriptyline.
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.
Rosalyn Carson-DeWitt MD, The Gale Group Inc., Gale, Detroit,