[Opsoclonus-ataxia syndrome in an adolescent: an acute otitis media complication].

Opsoclonus is defined as non-rhythmic, involuntary, spontaneous, multidirectional, and hyperkinetic eye movements, with a large amplitude and high frequency (10--15 Hz). These movements are present during visual fixation and convergence, and remain active during sleep and when the eyelids are closed. They should not be confused with an acquired nystagmus, which is usually unidirectional, with fast and slow components. In addition, opsoclonus is different from eye flutter, as this movement is restricted to the horizontal plane. The opsoclonus-myoclonus-ataxia syndrome (OMAS) is a rare condition characterized by opsoclonus associated with compensatory head movements, myoclonus, and cerebellar