迷路障害例の側方注視における眼と頭の協同運動異常

抄録

To examine the effects of labyrinthine disorders eye-head coordination, the lateral gaze tests and the alternate side-to-side gaze tests were performed on ll patients with acute unilateral labyrinthine lesions and five patients with bilateral labyrinthine lesions. The lateral gaze tests were also performed under the condition when a target disappeared during head movement (target flash mode). The patients were examined within 13 days after the onset of the disease in cases of unilateral lesions, and one to nine months in cases of bilateral lesions.
1. In the lateral gaze tests, 10 patients with unilateral lesions and all the patients with bilateral lesions showed abnormal gaze recordings in which the ratio of peak compensatory eye velocity to peak head velocity (VOR gain) was less than 1.0. Abnormal responses were divided into an overshoot type and a rounding type, whether the gaze overshot the target angle or not. The abnormalities were found on gazing toward the involved side in unilateral lesion cases and toward the right and left sides in bilateral lesion Cases.
2 The appearance rates of abnormal responses, especially in overshoot type, were remarkably higher in the target flash mode of the lateral gaze tests and the alternate side-to-side gaze tests than in the continuously illuminated target mode of the lateral gaze tests. However, in unilateral lesions, abnormal responses appeared markedly more frequently on gazing toward the involved side than the intact side.
3 The normal and abnormal responses at 40°-lateral gaze in a patient with unilateral lesion and a patient with bilateral lesions were analyzed for VOR gain, peak head velocities, amplitudes of initial saccades and gaze deviations at the ends of initial saccades. While normal responses were mostly found at relatively slow head velocities, abnormal responses appeared as the head velocity was large. The head velocity of the overshoot type tended to be larger than that of the rounding type. The amplitudes of initial saccades on gazing toward the involved side in unilateral lesions and on gazing toward the right and left sides in bilateral lesions were definitely smaller than those on gazing toward the intact side in unilateral lesions as well as normal subjects. This indicates that a recalibration of saccades to make the amplitude of initial saccades smaller than the target angle occurs as a compensatory process in labyrinthine lesions.
4. In most of the unilateral lesions, abnormal responses disappeared within six months in any test condition. However, abnormal responses were still frequently found in bilateral lesions even six months after the onset of the disease. Those results indicate the difficulty of compensation in bilateral lesions.