Computerized rotational vestibular testing in normal subjects

Background: As an integral part of the contemporary vestibular testing battery, computerized vestibular rotational testing provides physiologic stimuli and quantitative evaluation of the vestibulo-ocular reflex function of the horizontal semicircular canals. Clinically, it is most commonly used in the sinusoidal harmonic acceleration test (SHAT) and velocity step test. Because the results for a given subject may vary when tested using different facilities, the purpose of this study is to establish the normative data for our laboratory. Methods: Fifty-six normal subjects underwent the SHAT and velocity step test. Three parameters of SHAT - gain, phase and symmetry - were measured and recorded at 0.02, 0.05, 0.09 and 0.10 Hz. In the velocity step test, the three parameters of postrotatory nystagmus-time constant, maximum slow component eye velocity and directional preponderance were measured and recorded. Results: The means ± standard deviations of gain in the SHAT were 0.47 ± 0.16 at 0.02 Hz, 0.50 ± 0.16 at 0.05 Hz, 0.50 ± 0.16 at 0.09 Hz and 0.53 ± 0.17 at 0.10 Hz. The coefficient of variation for SHAT gain was 0.32. The time constant means and standard deviations in the velocity step test were 13.44 ± 3.53 and 13.52 ± 3.69 for clockwise and counterclockwise rotations, respectively. Conclusions: We conclude that computerized rotational vestibular testing is precise.