The Unusual Suspect: Artery of Percheron Occlusion in a Young Healthy Patient.

The artery of Percheron (AOP) is a rare anatomical variant. It is a single arterial trunk that supplies the bilateral thalami and midbrain. It is the result of an anatomical variant of the diencephalic irrigation in which the thalamic paramedian arteries arise with a common trunk from the posterior cerebral artery. The AOP is associated with a clinical syndrome characterized by bilateral vertical gaze palsy, memory impairment, and hypersomnia. Occlusion of the AOP can result in bilateral thalamic infarction with highly variable presentations that often mimic conditions such as encephalitis or metabolic disorders. This case report aims to highlight the diagnostic challenge and clinical significance of recognizing AOP occlusion in young patients presenting with acute confusion. We report here a case of a 24-year-old woman who presented with acute confusion but no focal motor deficit. Initial management targeted viral encephalitis, but magnetic resonance imaging confirmed bilateral thalamic infarcts, and magnetic resonance angiography demonstrated left occlusion of the AOP. Further evaluations identified a large patent foramen ovale (PFO) as the likely embolic source. The patient recovered with cognitive rehabilitation and returned to work within two months. This case illustrates the importance of including AOP occlusion in the differential diagnosis of acute confusion in young adults. In addition, it reinforces the need to conduct a thorough etiologic assessment for stroke in young adults, particularly evaluating for cardioembolic mechanisms such as the PFO.