RESUMEN
We report a 2 1/2-year-old girl who presented with acute history of fluctuating level of consciousness in the form of drowsiness, extreme irritability, and involuntary abnormal movements in the form of shaking of the whole body. She was treated with acyclovir empirically, contemplating Herpes simplex virus encephalitis. Overtime she improved substantially. The opsoclonus, myoclonus, and ataxia disappeared without treatment. However, 6 weeks later she presented again with classic opsoclonus-myoclonus syndrome. The investigations revealed neuroblastoma. This case illustrates that transient opsoclonus-myoclonus may occur with neuroblastoma and should not be assumed to be due to viral cause. Thus, a thorough search for occult neuroblastoma should be initiated even if opsoclonus-myoclonus resolves spontaneously