[The perverted nystagmus (author's transl)].

The perverted nystagmus is a modification of the horizontal beating nystagmus (in classical caloric stimulation) by a vertical or rotatory mainly component. Experimentally, this disorder can be shown after an unilateral destroy of the superior or median vestibular nucleus. We show 32 cases of subjects with a perverted nystagmus. 75% of these subjects have a pure central disease and 20% a vestibular neuronitis. The perverted nystagmus had an upbeat component with the cold stimulation and downbeat component with the hot stimulation. It was accompanied by a spontaneous nystagmus in 66% (and 30% with vertical nystagmus). Some abnormal responses with the simultaneous bilateral vestibular caloric testing, were found in 95%. The analysis of the results of the unilateral caloric testing shown the frequent association: hyporeflectia (canal paresis) of one side and hyper-reflects of the other side. This fact would have evoked a mixed disease, peripheric and central (i.e. the vestibular neuronitis). Beside some pathogenic hypothesis, we prefer the fall of the inhibiting control of the superior semi-circular canal firing activity. Although, the perverted nystagmus is a simple and precious examination sign (it is directly shown with Frenzel glasses after caloric vestibular stimulation. It ought to do the brain stem topography diagnosis.