聴神経腫瘍例における歩行時頭部運動の3次元動作解析

―特に末梢前庭機能との関係を中心に―

抄録

　Most acoustic neuromas (ANs) arise from the superior or inferior vestibular nerve. In our previous study, we demonstrated that the presence of vestibular disorders could cause unstable gait in patients with an AN. The purpose of this study was to investigate the influence of vestibular nerve function on head movements during walking. Fifteen patients (5 males, 10 females; mean age: 52.9±11.4 years old; mean height: 162.2±8.6cm) with unilateral AN were enrolled in this study. Nine healthy subjects (4 males, 5 females; mean age: 60.1±8.5 years old; mean height: 162.7±8.1cm) served as controls. All patients underwent ocular vestibular evoked myogenic potential (oVEMP), cervical VEMP (cVEMP), and caloric tests. Subjects were asked to walk at a comfortable speed with eyes open or closed. Head movements during walking were analyzed with a 3-dimentional motion analysis system. For the vestibular test results, the percentages of abnormal oVEMP, cVEMP, and caloric responses were 66.7% (10/15), 66.7% (10/15), and 73.3% (11/15), respectively. The oVEMP test results correlated well with the caloric test results. In comparison with horizontal head movements of normal subjects, those of AN patients, especially with abnormal oVEMPs in the eyes closed condition, were greater. Vertical head rotations (pitch movements) of AN patients, especially those with abnormal cVEMPs, were greater than those of normal subjects. These results suggest that the dysfunction of the vestibular nerve in patients with an AN could affect head stability during walking.