Internal carotid artery fenestration with contralateral internal carotid artery dissection: a case report and literature review.

Background: Internal carotid artery fenestration (ICAF) is a rare congenital cerebrovascular anomaly. Its coexistence with contralateral internal carotid artery (ICA) dissection is exceptionally uncommon, with only isolated case reports in the literature. The clinical features, hemodynamic characteristics, and optimal management of this rare combined lesion remain poorly understood. Conventional imaging alone cannot objectively evaluate lesion risk, so we report this case combined with hemodynamic analysis to clarify its pathogenesis and guide individualized treatment. Case presentation: We report a 71-year-old female who presented with episodic dizziness and had no history of hypertension or diabetes. Physical and routine laboratory examinations were unremarkable. Computed tomography angiography (CTA) suggested bilateral ICA C1 dissections. Digital subtraction angiography (DSA) confirmed a proximal fusiform dilation with intraluminal flow stratification (dissection) on the left C1 and a fenestration (two separate lumens with smooth intact walls) on the right C1. Computational fluid dynamics (CFD) analysis was performed to evaluate flow pressure (FP), wall shear stress (WSS), and oscillatory shear index (OSI). The left dissection showed significantly elevated FP, moderately elevated WSS at the entry and markedly elevated WSS at the exit, and high OSI. In contrast, the right fenestration demonstrated lower and uniformly distributed FP, relatively uniform WSS, and elevated OSI only in the smaller channel. Based on these findings, the left dissection was considered high-risk for rupture requiring active intervention, while the right fenestration was deemed hemodynamically stable and managed conservatively. The patient received dual antiplatelet therapy (aspirin 100 mg/d + clopidogrel 75 mg/d) for three days, followed by stent-assisted coiling of the left dissection. Her dizziness resolved completely after the procedure. Conclusion: Eight-month follow-up DSA confirmed complete resolution of the left dissection with preserved distal flow and stable morphology of the right fenestration. This case demonstrates that CFD hemodynamic analysis can help identify high-risk lesions and guide individualized treatment in patients with ICAF and contralateral dissection. Conservative management with antiplatelet therapy is appropriate for hemodynamically stable ICAF.