Small anterior circulation intracranial aneurysm rupture risk score

According to the ISUIA, small (<7 mm) unruptured intracranial aneurysm rupture risk of the anterior circulation (aC) carry a neglectable 5-years rupture risk. In contrast, some studies report frequencies of more than 20% of all ruptured intracranial aneurysm being small anterior circulation intracranial aneurysm. This contradiction was addressed in this study by analyzing the rates and risk factors for rupture of small IA within the aC.

Of the institutional observational cohort in the Essen University Hospital, 1676 small anterior circulation intracranial aneurysm were included. Different demographic, clinical, laboratory and radiographic characteristics were collected. A rupture risk score was established using all independent prognostic factors. The score performance was checked using receiver operating characteristic curve analysis.

Of all registered small IA of the aC, 20.1% were ruptured. The developed SIAAC score (range: -4 to +13 points) contained five major risk factors: IA location and size, arterial hypertension, alcohol abuse, and chronic renal failure. In addition, three putative protective factors were also included in the score: hypothyroidism, dyslipidemia and peripheral arterial disease. Increasing rates of ruptured IA with increasing SIAAC scores were observed: from 0% (≤-1 points) through >50% (≥8 points), and up to 100% in patients scoring ≥12 points. The SIAAC score achieved excellent discrimination (AUCSIAAC =0.803) and performed better than the PHASES score.

Small anterior circulation intracranial aneurysm carry a considerable rupture risk. After external validation, the proposed rupture risk score might provide a basis for better decision-making regarding the treatment of Small unruptured anterior circulation intracranial aneurysm ¹⁾