めまい症例における空間識の認識機能 正常人と末梢前庭障害における自覚的視性垂直位の比較検討

Abstract

The subjective visual vertical (SVV), that is, the visual orientation, was measured in forty normal healthy subjects, ten patients with acute Meniere's disease, eleven with Meniere's disease in remission phase, and five with vestibular neuronitis. The SVV was measured by the Rod and Frame test (RFT), which consists of a rod, which subjects rotate until they assume the bar to be vertical, and a frame, which leans 28 degrees to either the right or left to eliminate visual cues.First, the SVV, which was defined as a magnitude of error considering laterality, was measured in forty subjects and then again in 29 subjects to evaluate the normative response in eight trials. e.g., frame : 28 degrees tilted either to left or to right, rod : 28 degrees tilted either to left or right. The mean absolute value of SVV, which was defined as the magnitude of average error from true vertical regardless of laterality, was also calculated to determine the normal confidence limit. The SVV in the healthy group was quite small, and did not change on subsequent tests. The mean absolute SVV with no consideration of laterality in the healthy group was 1.2 degrees. While the SVV in the group with acute Meniere's disease was 5.9 degrees, 3.1 degrees in those in the remission phase, and 6.3 degrees in patients with vestibular neuronitis.The second parameter was frame dependency, and was defined as the condition in which laterality of SVV was consistent with that of the frame. Three of ten (30%) Meniere's disease patients in the acute stage, and three of eleven (27%) in the remission phase showed frame dependency. In contrast, the healthy group, and the vestibular neuronitis patients did not show frame dependency.From these results, we conclude that RFT is a useful device for measuring subjective visual vertical awareness of spatial orientation, and that visual disorientation is found in patient with vestibular disorders.