The Stroke That Hid in Plain Sight: Artery of Percheron Infarction With Bilateral Thalamic Involvement

We report the case of a 60-year-old woman with hypertension and poorly controlled insulin-treated type 2 diabetes mellitus who developed blurred vision followed by profound reduction in consciousness.She was subsequently found unresponsive at home and presented to the ED with a Glasgow Coma Scale score of 8/15, requiring emergency endotracheal intubation for airway protection.Urgent noncontrast CT of the head demonstrated no acute intracranial pathology.Following extubation, she exhibited marked drowsiness, bilateral ptosis, diplopia, and subsequently recognized vertical gaze palsy while limb strength remained relatively preserved.The ocular abnormalities initially broadened the differential diagnosis, while the persistent disturbance of consciousness prompted further investigation for central neurological causes.MRI subsequently demonstrated acute bilateral paramedian thalamic infarction with rostral midbrain involvement, consistent with an artery of Percheron (AOP) territory infarct.Following stroke team assessment, her National Institutes of Health Stroke Scale score was 3, reflecting vertical gaze palsy, left upper-limb incoordination, and dysarthria.She received secondary stroke prevention and multidisciplinary rehabilitation, with progressive improvement in consciousness, swallowing, and mobility, although residual visual symptoms persisted.The striking disparity between coma requiring airway intervention and the subsequent paucity of conventional focal neurological deficits illustrates an important diagnostic challenge of AOP infarction.A normal initial CT scan should not prematurely terminate investigation for posterior circulation ischemia when profound alteration in consciousness remains unexplained.