Impaired suppression of vestibular nystagmus by fixation of visual and acoustic targets in neurological patients.

Suppression of vestibular nystagmus induced by fixation of visual and acoustic targets moving with the head during sinusoidal rotation (0.1 Hz, 75 degrees/second peak velocity) was tested in cerebellar and noncerebellar patients. Visual suppression was impaired greatly in cerebellar patients, without correlation with visual smooth-pursuit defects. Acoustic suppression was equal to or slightly weaker than visual suppression. In noncerebellar patients, a disturbance of visual suppression was found only in the presence of a severe impairment of pursuit eye movements. Acoustic suppression did not parallel the visual-suppression pattern. In clinical vestibular examination, an impaired modulation of the vestibulo-ocular reflex suggests a cerebellar dysfunction, but also can occur in the presence of disorders of other parts of the CNS severely affecting the SP system.