Uncommon Association of Two Anatomical Variants of Cerebral Circulation: A Fetal-Type Posterior Cerebral Artery and Inferred Artery of Percheron, Complicated with Paramedian Thalamomesencephalic Stroke—Case Presentation and Literature Review

BACKGROUND: The unilateral fetal variant of the posterior cerebral artery (FPCA) is characterized by the congenital absence of the P1 arterial segment. The artery of Percheron (AOP) is an uncommon vascular variant, in which a single dominant thalamoperforating arterial trunk arises from one P1 segment, bifurcates, and provides bilateral supply to the paramedian thalami and rostral midbrain. CASE PRESENTATION: This is a retrospective case study of a 37-year-old man with multiple lifestyle risk factors (chronic marijuana and tobacco abuse), who suffered a thalamomesencephalic stroke, rapidly worsening to comatose state. After restoration of consciousness, he clinically manifested with left paramedian midbrain syndrome. Imaging demonstrated an asymmetric paramedian thalamic infarction with mesencephalon extension, patency of the basilar, vertebral arteries, and left PCA and right-sided FPCA, respectively. Left-sided thalamoperforating arterioles were not differentiated; AOP was inferred. Neither evident clinical source of embolus nor prothrombotic states were found. Mobile cardiac telemetry and transesophageal echocardiography were not available. The diagnosis was established too late for thrombolytic treatment. Anticoagulation was indicated during the acute and subacute stages, followed by low dose of antiplatelet. DISCUSSION: This uncommon cerebrovascular configuration (FPCA+AOP) might be the fourth case described in the literature. Sustained rehabilitation and abstinence from tobacco and cannabis led to favorable outcomes.