Comparison of Vestibule-ocular Reflex of Eccentric Rotation with Centric Rotation in Normal Subjects

ABSTRACT

BACKGROUND AND OBJECTIVES:Conventional vestibular rotation testing with the head centered on the axis stimulates the semicircular canals evoking compensatory eye movements. By placing subjects off from the axis of rotation, the otolithic organ may also be simultaneously stimulated by additional linear acceleration forces. In the present study, we compared the rotation with subjects placed on axis to those placed in an eccentric position. MATERIALS AND METHOD:In the eccentric rotation, the head of subject was facing outward and placed eccentrically for 33cm on naso-occipital axis. Slow harmonic acceleration test and velocity step test were performed. RESULTS:The sinusoidal eccentric rotation at 0.32, 0.64 Hz produced a significantly higher vestibulo-ocular reflex gain than did on axis rotation. In velocity step test, initial slow component velocity was significantly higher in eccentric rotation than in centric rotation. CONCLUSION:These finding suggest that the gain enhancement due to eccentric rotation is a result of tangentiallinear acceleration, probably sensed by the otolithic organ. This study raises the possibility of using eccentric rotation for the diagnosis of the patients with otolithic dysfunction.