Ocular counterrolling as an indicator of vestibular otolith function.

Sixteen normal subjects, 8 patients with unilateral vestibular nerve section, and 11 patients with acoustic neuromas underwent dynamic ocular counterrolling (OCR) testing. Both eyes were photographed at every 10 degrees as the subject was tilted about the naso-occipital axis at a constant velocity of 3 degrees/sec. Normal subjects differed from patients in four characteristics: (1) The binocular OCR patterns of normal subjects were consistent from one trial to the next. (2) The two eyes were mostly conjugate in movement. (3) The patterns were smooth. (4) OCR was approximately symmetric to right and left tilts. In the patients, patterns were abnormal when tilted to the side opposite the lesion. In quantified measures of the four characteristics, differences between the normal group and the group of patients with unilateral vestibular nerve sections were significant in consistency and total scores. In the patients with acoustic neuromas, OCR abnormalities corresponded to the size and location of the tumors and the extent to which they impinged on the utricular nerve and brainstem.