Reexamining Simultaneous Bithermal Caloric Irrigations as an Accurate and Comfortable Assessment of the Vestibular System

Abstract

Purpose: To determine if simultaneous bithermal caloric irrigations can be used as an accurate screening measure of vestibular function when compared to conventional alternating bithermal caloric irrigations. Additionally, to reassess if simultaneous caloric irrigations are considered more comfortable than alternating caloric irrigations.Methods: Twelve participants were asked to rate their baseline comfort levels using the Wong-Baker FACES scale, then underwent caloric irrigation testing. All participants were then irrigated six times under the following conditions: simultaneous warm water irrigations, simultaneous cool water irrigations, right warm water irrigations, left warm water irrigations, right cool water irrigations, and left cool water irrigations. Using an adapted Jongkees' formula, a criteria for abnormality was calculated; that is, the minimum difference in velocity of nystagmus that needed to exist between the ears in order to calculate a unilateral vestibular weakness above 20% was determined. The criteria for abnormality was then compared to velocity of nystagmus measured during simultaneous caloric irrigations. Additionally, participants were asked to rate their comfort level after ear irrigation, which was then compared using a Friedman’s Analysis of Variance by Ranks and pairwise comparisons. Results: Ten out of the twelve participants had normal results during alternating caloric irrigations, the majority of which showed nystagmus during simultaneous caloric irrigations that was measured below or close to the criteria for abnormality. Two out of the twelve participants showed abnormal results during alternating caloric irrigations; for simultaneous irrigations, one participant’s results were below the criteria for abnormality while the other participant was above the criteria for abnormality. A Friedman’s analysis indicated that differences in comfort ratings existed between the trials, and pairwise comparisons confirmed that simultaneous irrigations were rated more comfortable than conventional alternating caloric irrigations. Conclusions: Participants consistently rated simultaneous caloric irrigations as more comfortable than traditional alternating caloric irrigations. Data also suggested that simultaneous irrigations can be compared to conventional alternating caloric irrigations using a predicted difference value between the responses from each ear. Further data is needed to determine criteria for passing and failing results if simultaneous caloric irrigations are to be used as a clinical screening tool in vestibular evaluations.