Opsoclonus-myoclonus syndrome (OMS),also called Kinsbourne syndrome, dancing eyes syndrome, and myoclonic encephalopathy, is a rare neurobehavioral paraneoplastic disorder found in <4% of patients with neuroblastomas (Rudnick et al. 2001a; Gambini et al. 2003). The true incidence of OMS is unknown, with mild cases often being misdiagnosed (Everson and Cole 1956). Peak age of onset is 18-24 months, but the disease does appear across the age spectrum (Pranzatelli 2000). Children from all races, major socioeconomic groups, and geographic regions are affected (Pranzatelli 1992); males and females are affected equally. Opsoclonus and myoclonus are obligate features of the disease, but ataxia and other abnormalities are common. Tumors are often histolog-ically more mature, less aggressive, have favorable biology, and are associated with excellent rates of survival (Gambini et al. 2003). Most tumors are occult and may require repeated investigations for detection. Tumor removal is usually not therapeutic; indeed, some children worsen after surgery.
The clinical course is associated with a prodromal phase marked by extreme irritability, inconsolability, sleeplessness. During the acute neurological phase, the child suffers from incoordination and falling, with progressive neurological deterioration, inability to sit or stand, slurred speech rage attacks, hypotonia, head tilt, Horner's syndrome, deep tendon reflex abnormalities, or seizures. The chronic phase is associated with variable impaired cognitive function, IQ loss (Papero et al. 1995), attention deficit disorder with or without hyperactivity, obsessive compulsive disorder, mood and conduct disorders (Koh et al. 1994), speech articulation and fluency problems, ataxia (Mitchell et al. 2002), ocular flutter, and strabismus. Children with moderate and severe symptoms at the onset of OMS will not improve on their own and require immunotherapy. The "wait and watch" approach in this group following tumor resection is ill-advised (Blaes 2002).
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