The Artery of Percheron (AOP) is an uncommon but clinically significant anatomical variant in which a single arterial trunk supplies both paramedian thalami and, in some cases, the rostral midbrain. Occlusion of this vessel can produce bilateral thalamic infarction—a striking but often under-recognized pattern—leading to presentations that mimic encephalitis, toxic-metabolic encephalopathies, or psychiatric conditions. Because this constellation of symptoms frequently lacks obvious focal neurological deficits, early diagnosis is challenging, particularly in young adults where stroke is not typically the first consideration.

We present the case of a 24-year-old woman who arrived with abrupt-onset confusion and profound disorientation but no motor weakness or cranial nerve deficits. Initial clinical suspicion favored viral encephalitis, prompting empiric treatment. However, as her condition evolved, magnetic resonance imaging revealed symmetric bilateral thalamic infarcts. Subsequent magnetic resonance angiography demonstrated left-sided occlusion of the AOP, confirming a rare vascular etiology. Given her age and absence of traditional vascular risk factors, an expanded etiologic workup was pursued. This evaluation uncovered a large patent foramen ovale (PFO), ultimately identified as the probable embolic source.

The patient underwent targeted stroke management and cognitive rehabilitation, achieving a full return to work within two months—highlighting the potential for meaningful recovery when timely diagnosis and tailored treatment are provided.

This case underscores two important messages for clinicians: First, AOP occlusion should be considered in any young patient presenting with unexplained acute confusion, hypersomnia, or vertical gaze abnormalities, even in the absence of focal deficits; second, stroke in young adults warrants a comprehensive search for atypical or cardioembolic mechanisms, particularly PFO-related embolism. Recognizing this rare but life-altering condition is essential for initiating appropriate therapy and optimizing patient outcomes.

May Thet Htar Zon earned her M.B., B.S degree from the University of Medicine 1, Yangon, Myanmar. She completed her full Membership of the Royal Colleges of Physicians (MRCP) in 2019. She has over three years of clinical experience working as a Stroke and General Medicine Registrar within the NHS, where she has developed a strong interest in cerebrovascular diseases in young adults. Her commitment to advancing stroke care is reflected in her clinical work as well as her academic contributions. She published a case report on young stroke in the Cureus medical journal in November 2025. She continues to integrate clinical practice, research, and education with the aim of improving early recognition and management of stroke.