[Significance of the Bárány convection hypothesis for thermal nystagmus. Quantitative comparison of the intensity of thermal nystagmus in supine and prone position].

The hypothesis of Bárány explaining thermic nystagmus has been shaken. We must accept a non-convective triggering of nystagmus in extraterrestrial space. Under terrestrial conditions, however, the reversibility of the thermic nystagmus by changing from supine to prone position continues to support the convection hypothesis. We examined the nystagmus intensity in the supine and prone position with 22 healthy ears. The thermic stimulus was monitored via computer-controlled alternating irrigation system. The sequence of examinations was randomised and the evaluation of the nystagmus effected by automatic analysis. Our data allow to assess the importance of the non-convective nystagmus. With clinical test conditions about 85% of the maximal thermal reaction can be explained by the convection hypothesis of Bárány. However, interindividual variance is considerable, and one exceptional case with predominantly non-convectively released nystagmus is presented.