Lesson of the month 1: Artery of Percheron occlusion - an -uncommon cause of coma in a middle-aged man.

Bilateral paramedian thalamic infarction resulting from artery of Percheron occlusion presents with a distinct clinical syndrome comprising impaired consciousness, often with vertical gaze palsy and memory impairment. This uncommon anatomical variant arises as a single artery supplying both paramedian thalami. Early recognition can be challenging in the obtunded patient, where the differential diagnosis is broad. The acute physician should consider this diagnosis in a patient presenting with unexplained coma so that emergent treatments such as thrombolysis can be employed. Early imaging with computerised tomography can often be normal; therefore the use of magnetic resonance imaging is essential in confirming the diagnosis. © Royal College of Physicians 2016. All rights reserved.