Clinical Implication of High VOR Gain in Slow Harmonic Acceleration

Suh, Myung Whan; Kim, Yun Ho; Jung, Jae Yun; Rhee, Chung Ku

Abstract

BACKGROUND AND OBJECTIVES
The purpose of this study was to verify if high vestibulo-ocular reflex (VOR) gain in slow harmonic acceleration (SHA) test can be considered as a hallmark of a distinct disease entity. We hypothesized that patients with high VOR gain in the SHA test can be classified as a distinct disease group and looked for evidence that can support this hypothesis.
SUBJECTS AND METHOD
For this study, 306 patients who had undergone a rotation chair test were enrolled. We checked other VOR measurements (caloric test and step velocity) and clinical manifestation of the patients with high gain in SHA (HG group). The data were compared to those of the migraine associated vertigo (MAV), benign recurrent vertigo (BRV) and psychogenic dizziness (PsyD).
RESULTS
An abnormally long time constant and a large response to the caloric test were found more frequently in the patient group with high gain in SHA. The incidence of high gain in SHA was significantly higher in MAV, BRV and PsyD. The clinical manifestation of HG group was not distinguishable from the effects of BRV and PsyD. But MAV was different from HG group.
CONCLUSION
We failed to find any evidence that the patients with high gain in the SHA could be classified as a distinct disease group. It seems that high gain is not merely a non-specific or incidental finding but a reproducible finding that reflects an aspect of the subject's vestibular function. Also, the high gain in SHA is more suggestive of BRV or PsyD than MAV.