IntroductionRecent data has identified that certain risk factors for rupture differ between small and larger intracranial aneurysms (IAs). Such differing risk factors make up 5 out of the 6 predictor variables used in the PHASES score which raises the question on whether IA size has a significant effect on the score’s performance. MethodsPatients which were diagnosed with an IA incidentally or due to a subarachnoid hemorrhage (SAH) between 2015-2023 were selected for potential inclusion. The median IA size of the cohort was chosen as the cutoff point to categorize small and large (6 mm). The PHASES score was calculated for all patients and a receiver operating characteristic curve analysis was performed to evaluate the classification accuracy of PHASES in predicting rupture for small and large IAs. ResultsA total of 677 IAs were included. Among the IAs, 400 (58.9%) presented as UIAs and 279 (41.0%) as SAH. The average PHASES score was 2.9 and 6.5 for small (n = 322) and large (n = 355) IAs, respectively. The PHASES score performed significantly lower for predicting rupture in smaller IAs (area under the curve [AUC]: 0.634) compared to the larger (AUC: 0.741) (p = 0.00083). ConclusionPHASES was shown to underperform on small IAs. The decision to treat small unruptured IAs remains highly controversial and the development of a new score to estimate the annual rupture rate while accounting for IA morphology is of great need. Our findings can help encourage future researchers to develop such a score.
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