Objectives To present a case of bilateral thalamic ischaemic strokes in an elderly gentleman due to occlusion of the artery of Percheron, a rare anatomical variant in which a single branch of the posterior cerebral artery supplies the paramedian thalami bilaterally, as well as parts of the rostral brainstem and anterior thalamus.¹

Methods A retrospective case review was performed of a patient diagnosed with artery of Percheron occlusion causing bilateral thalamic ischaemic strokes to demonstrate the clinical and radiological features of this unusual syndrome.

Case An elderly gentleman presented to the emergency department after developing slurred speech and collapsing at home. His level of consciousness was fluctuating with a Glasgow Coma Scale score ranging from 3 to 9 (E1, V2, M6) and his pupils were reactive but unequal. Subsequently he was noted to have vertical gaze palsy and profound short term memory impairment. Initial CT imaging including a CTA was unremarkable. An MRI brain demonstrated bilateral medial thalamic infarcts suggestive of occlusion of the artery of Percheron. The clinical features fitted with the triad of vertical gaze palsy, memory impairment and coma described in previous cases of artery of Percheron occlusion.² The patient was subsequently diagnosed with infective endocarditis with four sets of blood cultures positive for Staphylococcus capitis. A transoesophageal echocardiogram demonstrated multiple vegetations on his bioprosthetic aortic valve and a bone scan was suggestive of C5/6 discitis. Despite treatment, he later developed further areas of infarction in the basal ganglia and right parieto-occipital cortex. His condition eventually stabilised and he was discharged to a rehabilitation unit.

Conclusions The artery of Percheron is a rare anatomical variant of the posterior cerebral circulation, occlusion of which causes bilateral thalamic ischaemic strokes. This is characterised by the clinical triad of vertical gaze palsy, memory impairment and coma.