Dysrhythmia of caloric nystagmus.

Abstract

Objectives of the study were 1) to determine the prevalence and characteristics of dysrhythmia, 2) to identify associations between dysrhythmia and other patient variables, and 3) to determine whether dysrhythmia is more a characteristic of individuals than simply a correlate of alertness or response intensity. Cross-sectional. Review of records from 150 patients undergoing the caloric test. Dysrhythmia severe enough to interfere with accurate analysis of the caloric test was present in 40% of the cases. Individuals were entered into an "orderly" group (n = 67) or a "dysrhythmic" group (n = 83) and were 5.8 times more likely to remain in the same group on a second visit than to change groups. Stronger response scores were associated with less dysrhythmia. Higher caloric-induced vertigo scores were associated with both stronger response scores and lower dysrhythmia scores. Cases in the dysrhythmic group were 3.8 times more likely to have abnormal caloric test results than individuals in the orderly group. Dysrhythmia frequently interferes with valid and accurate interpretation of the caloric test. Current methods of "mental alerting" frequently fail to eliminate dysrhythmia. The presence of dysrhythmia appears to be a strong predictor of an abnormal caloric test result, and there is a moderate correlation between dysrhythmia and response intensity. Nevertheless, our results suggest that dysrhythmia is specific to individuals, rather than simply a manifestation of peripheral vestibular disease or a correlate of alertness or response intensity.