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.