Prerupture Intracranial Aneurysm Morphology in Predicting Risk of Rupture: A Matched Case-Control Study

BACKGROUND: Maximal size and other morphological parameters of intracranial aneurysms (IAs) are used when deciding if an IA should be treated prophylactically. These parameters are derived from postrupture morphology. As time and rupture may alter the aneurysm geometry, possible morphological predictors of a rupture should be established in prerupture aneurysms. OBJECTIVE: To identify morphological parameters of unruptured IAs associated with later rupture. METHODS: Nationwide matched case-control study. Twelve IAs that later ruptured were matched 1: 2 with 24 control IAs that remained unruptured during a median follow-up time of 4.5 (interquartile range, 3.7-8.2) yr. Morphological parameters were automatically measured on 3-dimensional models constructed from angiograms obtained at time of diagnosis. Cases and controls were matched by aneurysm location and size, patient age and sex, and the PHASES (population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from another aneurysm, and site of aneurysm) score did not differ between the 2 groups. RESULTS: Only inflow angle was significantly different in cases vs controls in univariate analysis (P =.045), and remained significant in multivariable analysis. Maximal size correlated with size ratio in both cases and controls (P =.015 and <. 001, respectively). However, maximal size and inflow angle were correlated in cases but not in controls (P =.004. and .87, respectively). CONCLUSION: A straighter inflow angle may predispose an aneurysm to changes that further increase risk of rupture. Traditional parameters of aneurysm morphology may be of limited value in predicting IA rupture.