Physiological Postrotatory Nystagmus

Abstract

Nystagmus elicited by means of rotatory stimuli has been studied in 55 healthy subjects. In each case, 5 different end-velocities have been employed and each postrotatory nystagmus has been quantitatively evaluated measuring various parameters of its quick phase. The relationship existing between the magnitude of the stimulus and that of the response has been carefully studied for all the parameters. A significant relationship was found in only a limited number of cases. The most reliable parameter to analyse this relationship is the total amplitude. The parameter that varied less with changes in stimulus intensity was duration. The different factors determining and modifying the nystagmic response are analysed and the meaning of this nystagmic response is considered in relation to vestibular function and, therefore, in its application to clinical diagnosis. In a previous article [16], the authors analysed the normal values of various parameters of postrotatory nystagmus in healthy subjects and the differences existing between clockwise and counterclockwise rotations. In this paper, we study the relationship between the intensity of the stimulus and the magnitude of the response. We also investigate which parameters are the most adequate to define the nystagmus.