Reevaluating Order Effects in the Binaural Bithermal Caloric Test

Abstract

Purpose The purpose of this study was to determine whether a significant order effect exists in the binaural bithermal caloric test. Method Fifteen volunteers (mean age = 24.3 years, range = 18–38 years) with no history of vestibular disorder, hearing loss, concussion, or neurological disease underwent caloric testing on 3 occasions. Irrigations were randomized using 8 possible order combinations. The parameters of interest included unilateral weakness, directional preponderance, total response from the right ear, and total response from the left ear. Results Order effects were analyzed using 2 methods. The first analysis was done looking at the 8 possible orders. We also had an a priori established hypothesis that the first irrigation tested would influence the calculation of unilateral weakness more than the other 3 irrigations. To test this hypothesis, the 8 orders were condensed into 4 order conditions based on the first irrigation. The effect of order was determined using analysis of variance tests. Although the first irrigation tended to be the largest, no significant effects were observed. Conclusions This experiment demonstrated that while there is great inter-individual and intra-individual variability in caloric test results, the order of irrigations had no significant effect in the test. Future studies may explore the effects of nonphysiological factors on test results.