Which are the parameters of choice from the evaluation of caloric nystagmus?

On hand of caloric tests on 202 healthy subjects, the coefficient of correlation between the currently most frequently used intensity parameters was established separately for each of the four irrigations, i.e. between maximum velocity of the slow phase, maximum amplitude, maximum frequency, total number of beats and duration of reaction. The maximum velocity of the slow phase is so closely correlated to the maximum amplitude, and the maximum frequency is so closely correlated to the total number of beats (r = always greater than 0.75) that it is sufficient to merely determine one of the two well correlated parameters in healthy subjects. However, the parameters maximum velocity of the slow phase and maximum amplitude are less closely correlated to the parameters maximum frequency and total number of beats (r = smaller, in part considerably smaller than 0.75). A better correlation exists between the nystagmus parameters nearly always by warm irrigations, as compared to cold ones. The findings speak for the fact that maximum velocity of the slow phase and maximum amplitude on one hand, and maximum frequency and total number of beats on the other, are an expression of various characteristics of the experimental nystagmus. In a consecutive publication, we are going to report in which way the various nystagmic parameters of patients are being changed by different lesions of the vestibular system.