ASSESSMENT OF OTOLITH FUNCTION BY USING S UBJECTIVE VISUAL VERTICAL ANALYSIS

This report summarizes our experiences with the subjective visual vert ical (SVV) as a clinical neuro-otological tool. In the 5W test, patien ts have to orient a dim light bar in an otherwise dark surrounding ear th-vertical, using a remote-control. Normal subjects in an upright pos ition did not deviate more than 2 degrees from true vertical. Af-ter v estibular neurectomy,the SW was consistently tilted by some 12 degrees toward the affected ear. Smaller tilts (similar to 7 degrees) of the SVV occured in patients with spontaneous peripheral vestibular disease s. This shift in SVV disappeared within weeks to months, similar to th e spontaneous nystagmus. After stapes surgery slight deviations of the SW towards the unoperated ear were seen in about 20% of the patients, indicating a slight irritation of the otolith organs. Assessed in an upright position,the SVV thus may be regarded as reflecting tonic otol ithic input differences between the two ears. Asymmetries in the shift s of the SW induced by roll tilts of the gravito-inertial vector by ec centric rotations of the subject have been proposed as a test for otol ithic sensitivity. in our studies such asymmetries in the shifts of th e 5W could not be induced by 26 degrees or 90 degrees roll tilts of su bjects towards the affected or healthy ears. A simple clinical test to reveal unilateral otolithic sensitivity (comparable to an otolithic ' 'caloric test'') thus still has to be found.