Closed-loop caloric, harmonic acceleration and active head rotation tests: norms and reliability

Norms and test-retest data from 20 persons with normal hearing and balance function were obtained for bithermal caloric (BC) using a closed-loop irrigator, sinusoidal harmonic acceleration (SHA) and active head rotation (AHR) tests. Each subject was tested twice with each test, with at least 24 hours between retest. Results of BC testing indicate that a unilateral weakness of 30% should be present to confidently identify a significant inter-ear difference when using a closed-loop irrigator for stimulus. Test-retest correlations of unilateral weakness were extremely poor, reflecting the potential for considerable variability with this test. With the exception of asymmetry measures at 0.01 and 0.02 Hz, SHA gain, phase, and asymmetry are very similar to previously published norms. Test-retest correlations were generally better than BC correlations, with phase measures having the highest test-retest correlations. AHR norms were obtained in three conditions, with eyes open and starting at a stationary target (AHR-EO), with eyes closed (AHR-EC), and with eyes open and fixated on a target moving synchronously with the head (AHR-FX). AHR-EO mean gain and phase were slightly less than that reported by other researchers, possibly as a result of differences in analysis algorithms, and had the poorest test-retest correlations. AHR-EC gain and phase were much more variable than AHR-EO between subjects, but showed very high test-retest correlations. AHR-FX gain, phase, and asymmetry are similar to those reported previously and have slightly better test-retest correlations than AHR-EO.