Testing of otolith function.

In order to investigate otolith function, horizontal eye displacement in total darkness during tilting laterally about body axis was examined in 23 normal subjects and 29 patients with vestibular lesions. The mean and standard deviation of this eye displacement in normal subjects were 18.9 + 6.1 degrees at 15 degrees of body-tilt. Thus, eye displacement below the lower tolerance limit of normal eye displacement at 15 degrees of body-tilt, that is, 8.8 degrees, was judged to be abnormal. Meanwhile, 12 cases or 41.4% of 29 patients with vestibular lesions showed abnormal eye displacement in this test. Especially in cases with positional vertigo and/or dizziness, the occurrence of abnormal results in this test (69%) was far higher compared with that of cases where vertigo and/or dizziness was not associated with postural changing (19%). Therefore, these abnormal results seem to be closely related to the disorder of otolith system.