抄録
In this study conditions necessary for inducing horizontal positioning nystagmus were investigated. These conditions were the speed of head rotation (slow or quick), the plane of head rotation (frontal, sagittal or horizontal), the angle of the axis of head rotation with gravity (head rotation in the horizontal plane in the sitting position or in the supine position) and the direction of head rotation. The results suggest that an essential condition is the velocity of head rotation in the perpendicular plane to provoke horizontal positioning nystagmus and that lesions in the cupulo-endolymph system are not responsible for horizontal positioning nystagmus. It was speculated that unilateral utricle dysfunction (such as separation of otoconia from the otolithic membrane) might be the primary cause of the pathophysiology. So head rotation in the perpendicular plane might send a mistaken velocity signal to the central nervous system and finally provoke horizontal positioning nystagmus related to head velocity. It may be that a velocity signal is formed in the central nervous system when one detects a moving pattern that occurs as utricular afferents with different polarization vectors are excited sequentially by a rotating gravity vector (Raphan T and Cohen B 1981).
