319 - Artery of Percheron Occlusion

A previously independent 95-year-old woman presented to the emergency department after being found unresponsive. MRI brain revealed foci of restricted diffusion within the medial thalami bilaterally, left more extensive than right. Findings showed subacute infarction consistent with an anatomic variant of a single vessel arising from the basilar apex supplying the thalami bilaterally known as an artery of Percheron (AOP). On presentation to the emergency department, the patient was only responsive to noxious stimuli with subtle right-sided hemiparesis, and right-sided hyporeflexia, but was not responsive enough for formal testing. On admission to acute rehabilitation after a nine-day hospital course, the patient was noted to be encephalopathic with gait instability, dysarthria, dysphagia, and expressive and receptive aphasia.

Discussions:

The paramedian thalamus and midbrain are generally supplied by two separate ipsilateral branches off the first segment (P1) of the posterior cerebral artery (PCA).  An infarct of the thalamus can present as a unilateral pure sensory stroke. Infarct of the midbrain can result in Weber’s Syndrome with ipsilateral paralysis of cranial nerve three, contralateral hemiplegia, and ataxia. AOP is a rare anatomic variant where bilateral paramedian thalami and midbrain are supplied by one unilateral branch off P1. Most AOP strokes go undetected on routine imaging, especially if signs and symptoms are subtle. Occlusion of the AOP can result in bilateral thalamic infarcts with midbrain involvement yielding a unique presentation as seen in this patient.  Presentation additionally impacts the rehab course as patients may not have a functioning unharmed side for compensation, typically seen in a unilateral stroke.

Conclusions:

While this anatomic variant is uncommon it is important to be aware of the presentation of AOP territory infarct due to its atypical symptom manifestation and to recognize associated barriers in rehab.