Comparative Study of Caloric Responses Induced by Different Stimulus Intensities

Abstract

Bithermal caloric responses induced by 20, 50 and 240 ml water irrigations were compared in 111 healthy Japanese adults. Distribution mode of max. slow phase eye velocity (SPEV), duration and max. frequency showed normal pattern in the logarithmic scale but not in the regular scale. All three nystagmus parameters of 240 ml caloric test showed most linear distribution compared with two other caloric tests in the probit plots of logarithmic scale. When the mean, coefficient of variation and normal range (mean ±2 SD) were compared between two modes of distribution, the most consistent difference was found in the range which was biased to the side of large number with little difference in the width of the range. When one standard deviation of CP- and DP-indexes were compared, these values were smallest in max. frequency, however, the best negative correlation between variation (SD) of CP- and DP-indexes and stimulus intensity was found in SPEV.