392 Validation of a Mathematical Model for Rupture of Spherical Intracranial Aneurysms

INTRODUCTION: An accurate mathematical model of intracranial aneurysm (IA) mechanics is of great value for its potential utility in assessing probability of IA rupture, thus informing the decision to pursue surgical intervention with its associated risks. Such a model for spherical IAs has been proposed which predicts a wall-thickness-to-IA-radius ratio (WTR) of 6.1*10-3 at which IAs rupture (Chaudhry et al. 2006). To our knowledge, no further work has been done to validate this model with clinical data. We assess the accuracy of this model using cases of ruptured and unruptured IAs. METHODS: Aneurysm height, width, neck diameter, and vessel radius were measured on CTAs/MRAs/DSAs of IAs of the basilar tip, anterior communicating, and posterior communicating arteries. Binary logistic regression analysis was performed to determine the WTR where there is a 50% probability of rupture. RESULTS: 52 unruptured and 28 ruptured spherical IAs were included. Binary logistic regression revealed a strong association between decreased WTR and rupture status. The point at which there is a 50% chance of rupture was found to be WTR = 8.6*10-3, from which the proposed 6.1*10-3 differs by only 29%. CONCLUSIONS: The model for IA rupture mechanics proposed by Chaudhry et al. agrees reasonably well with clinical data and could serve as a foundation upon which further investigation may be based. This study was limited primarily by its method of approximating aneurysm wall thickness, which may have over- or under-estimated the actual thickness. Future studies may improve on this by utilizing direct measurements of wall thickness through histological examination.