Sinusoidal harmonic acceleration.

The need for accurate and reliable diagnostic tests for the evaluation of vestibular function has stimulated investigation of rotational methods and more recently, an evaluation of harmonic angular acceleration. Initial studies, using these techniques in humans, demonstrated a linear input-output function from 0.24 to 0.04 cycles/s at 0.4 radians/s2, but a reduction in the increase of response with an increase of acceleration or a decrease of frequency from this range. Nystagmic responses were symmetrical in these same normal individuals. In patients with vestibular disease, input-output functions, as well as symmetry, were altered, and appeared related to the degree of pathology. Evaluation of the test system in animals, rendered ototoxic with streptomycin, showed a depression in response similar to caloric tests. All data suggested that harmonic angular acceleration provided a reliable and sensitive method for evaluation of vestibular function, and a useful and important confirmation to the other methods that are available for these evaluations.