Horizontal eye movement disorders after posterior vermis infarctions.

The horizontal saccade, smooth pursuit, and vestibulo-ocular reflex gains were recorded in 19 patients with cerebellar infarction documented with MRI, and in a group of control subjects. Bilateral saccade hypometria and a decrease in ipsilateral smooth pursuit gain were found only in patients with a lesion affecting the posterior vermis. These results in humans support experimental findings suggesting that the posterior vermis controls both saccade accuracy and smooth pursuit velocity.