Velocity of rapid eye movements and vertigo of central origin.

Peak velocities of voluntary saccades and fast phases of different qualities of nystagmus were studied in 20 normal subjects, 5 patients with pontine lesions and 5 patients with lesions in the frontal cortex. The peak velocity of saccades was related to the amplitude of the eye movement, the alertness of the subject and whether the subject could see the target or not. The effect of the age was not significant. The quick phases of caloric, optokinetic and angular acceleration induced nystagmus were equally rapid but somewhat slower than that of vestibular nystagmus recorded in standardized visual surrounding. In the same visual condition saccades were always faster than quick phases of nystagmus. Patients with cortical lesions had normal velocities in saccades and quick phases of nystagmus. Patients with pontine disorders had significantly reduced saccadic and quick phase velocity, and some of the patients exhibited dissociations between velocity mechanisms while the somewhat higher velocity in quick phase of vestibular nystagmus recorded in light is probably related to higher attention evoked by vestibular-visual interaction.