Complex Cerebral Artery Anomaly Rete-like Formation of the Terminal Carotid and Middle Cerebral Arteries with Bilateral A1 Segments Fenestrations

We present a rare case of a 16-year-old male who was admitted with bilateral tinnitus and subsequently underwent magnetic resonance imaging (MRI) and digital subtraction angiography (DSA) for further evaluation. The left internal carotid (ICA) artery had a normal caliber but ended as a stump at the C7 segment, with a network of filiform vessels from both the stump and right posterior communicating artery (PComm). The right PComm was hypertrophic and the right posterior cerebral artery (PCA) was mainly supplied by the right ICA. The right ICA's bifurcation and the initial middle cerebral artery (MCA) segment were absent, while the MCA trunk was hypoplastic. The right PCA and pial branches vascularized the temporal lobe, with collaterals between the PCA and MCA. The left ICA was slightly enlarged with double fenestration at the left A1 segment. The right A1 segment of the anterior cerebral artery had double fenestration and while several diagnoses were considered, no single diagnosis fully explained all clinical findings. A thorough review of the existing literature yielded no comparable cases, highlighting the uniqueness of this presentation. This case emphasizes the complexity of cerebral vascular anomalies and the challenges associated with diagnosing such rare conditions, underscoring the need for careful assessment.