A Case of Diagnostic Difficulty: Transient Loss of Consciousness in Artery of Percheron Infarct.

The artery of Percheron (AOP) is a rare anatomical variant of the paramedian thalamic vessels in 7-10% of the general population. An AOP infarct can present with rare clinical manifestations like transient loss of consciousness (LOC) and lethargy, as was seen in the patient whose case is discussed in this report, due to the plethora of regulatory inputs and outputs by the thalamus, which cannot be compensated for because of the absence of anastomotic connections. The AOP supplies the reticular activating system (RAS), which regulates consciousness. Ischemia to this area from an AOP infarct can result in the transient LOC, which our patient experienced. The AOP is a small vessel that is often missed on a CT angiogram (CTA) alone due to low resolution. As a result, it is imperative that clinicians utilize MRI to diagnose AOP infarcts in patients who present with symptoms that raise concerns for decreased bilateral thalamic function and transient LOC.