Eye-velocity programming in brain-stem disorders.

Eye movements in 30 patients with brain-stem lesions were evaluated with electro-oculography, and the findings were analyzed with regard to the site of the lesion in the brain stem. Eye velocities generally were reduced more severely in pontine than in medullary lesions. In medullary lesions, there even was a slight enhancement of the velocities in the fast component of optokinetic and postrotatory nystagmus. In contrast to the slow-phase velocity of OKN, which often was preserved in medullary lesions, the smooth-pursuit velocity was reduced in lesions at all levels in the brian stem. This indicates that these two types of visually induced eye movements use different mechanisms.