Transient Upbeat Nystagmus Due to Unilateral Pontine Infarction

ABSTRACT

Upbeat nystagmus has been described in bilateral lesions of the medulla, the ventral tegmentum, the anterior cerebellar vermis, the adjacent brachium conjunctivum, and the midbrain. Imbalance of the vertical vestibulo- ocular reflex (VOR) favoring the downward VOR activity would therefore result in upbeat nystagmus. We report a patient with transient upbeat nystagmus due to unilateral pontine infarction that may have disrupted bilateral upward VOR pathways running in the ventral tegmental tracts.