We describe a 40 year-old male with a ball-cage mitral valve prosthesis who suddenly developed bilateral ptosis, bilateral dilated and unreactive pupils, right third nerve palsy, bilateral failure of vertical gaze, somnolence and mild ataxia without major motor deficits. Computed Tomography (CT) revealed bilateral thalamic infarcts in the distribution of the rostral basilar artery. Infarction in this case occurred despite adequate anticoagulation. The recognition of the entity of rostral basilar artery occlusion is important as interruption of anticoagulation may be avoided.