Are the Small Intracranial Aneurysms of the Anterior Circulation Score Sensitive Enough to Discriminate Aneurysms at High Risk of Rupture? Retrospective Analysis of 193 Ruptured Aneurysms

BACKGROUND AND PURPOSE: The Small Intracranial Aneurysms of the Anterior Circulation (SIAAC) score was proposed in 2023 to stratify the rupture risk of small (<7 mm) intracranial aneurysms of the anterior circulation and guide the decision-making process. However, external validation of the SIAAC score, which is critical for the responsible clinical application of the predictive model, is still lacking. Our objective was to assess the capability of the SIAAC score to discriminate intracranial aneurysms with a high propensity for rupture in a large cohort of patients admitted for a proven SAH. MATERIALS AND METHODS: Between 2012 and 2022, we included all consecutive adult patients admitted to our institution for an SAH caused by the rupture of a <7-mm saccular intracranial aneurysm of the anterior circulation. After we calculated the SIAAC score, patients were labeled as "true-positives" if the SIAAC score would have (appropriately) predicted a "high" or "intermediate" risk of rupture, whereas patients for whom the SIAAC score would have (inappropriately) estimated a "low" or "no" risk of rupture were labeled as "false-negatives." The sensitivity of the SIAAC score was calculated by using the following formula: True-Positives/(True-Positives + False-Negatives). RESULTS: A total of 193 patients (63% women; mean age, 64 [SD, 14.3] years) were incorporated into the final analysis. There were 126 true-positives (65.3%) and 67 false-negatives (34.7%), leading to a sensitivity of the SIAAC score of 65.3%. CONCLUSIONS: In the event of intracranial aneurysm discovery before rupture, application of the SIAAC score would not have accurately stratified rupture risk (and thereby proposed appropriate management) in a substantial proportion of patients.