Artery of Percheron infarction presented with isolated downgaze paralysis: A case report.

Isolated downgaze paralysis is the most infrequent expression of vertical gaze abnormalities. Vertical eye movements are controlled by nuclei and circuits located in the thalamic-mesencephalon region, and more particularly the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). The Artery of Percheron (AP) is a rare vascular anatomic variation that supplies the paramedian region of the thalami and the rostral portion of the mesencephalon. We present a unique case of isolated downgaze paralysis caused by AP ischemia.