Imaging of acute bilateral paramedian thalamic and mesencephalic infarcts.

Thalami and midbrain arterial supply arises from many perforating blood vessels with a complex distribution for which many variations have been described. One rare variation, named the "artery of Percheron," is a solitary arterial trunk that arises from one of the proximal segments of a posterior cerebral artery and supplies the paramedian thalami and the rostral midbrain bilaterally. Occlusion of this artery results in bilateral thalamic and mesencephalic infarctions. We describe three patients with a presumed occlusion of the artery of Percheron in whom MR imaging showed characteristic symmetrical bilateral paramedian thalamic and mesencephalic infarctions.