Introduction: Prediction of rupture risk for intracranial aneurysms remains inconsistent. Our ability to identify patients at risk for subarachnoid hemorrhage relies on an imprecise set of “predictive” factors, such as aneurysm size, location, and family history. We use a geometric approach to explore the risk factors associated with rupture of very small aneurysms (< 4mm), which are routinely observed when found incidentally.
Methods: Patients with ruptured or unruptured intracranial aneurysms treated at North Shore University Hospital (NSUH) in Manhasset, New York, from 2010 to 2013 were identified. Aneurysms measuring less than 4mm from neck to dome (dmax) were analyzed with a focus on aneurysm dimension, incident angle, and parent vessel geometry. Measurements were conducted by two independent investigators using DSA, CTA, or MRA, and parameters were analyzed for significance using multivariate logistic regression analyses
Results: A total of 344 aneurysms were identified, and 60 ruptured and 55 unruptured aneurysms < 4mm were compared. A statistically significant difference in afferent to efferent parent vessel diameter ratio (AER) was found between ruptured and unruptured aneurysms, with smaller AER being predictive of greater risk (1.14 vs 1.31, p = 0.01). Dome-to-neck (DTN) and dmax-to-neck (DMN) ratio were found to be statistically significantly larger in ruptured vs. unruptured aneurysms less than 4mm (p=0.02 and p=0.05, respectively). Aneurysm angle was demonstrated to be directly correlated with risk of rupture with increasing divergence from the golden ratio (? = 137.5°; p = 0.02). In fact, for every change in aneurysm angle of 10°, there is and 8.5% increase in risk of rupture (p=0.04).
Conclusions: Patients who present with aneurysms < 4mm with large DTN or DMN ratios should be considered for early intervention. Moreover, aneurysms with angles that differ significantly from the golden ratio (? = 137.5°) should also be considered for early treatment.
Patient Care: we hope to improve our ability to identify risk factors for aneurysm rupture in patients with very small aneurysms such that early intervention can be utilized in high risk patients and not risked in those with low risk
Learning Objectives: By the conclusion of this session, participants should be able to: 1) understand the importance of small aneurysm rupture risk; 2) identify key morphologic parameters that may predict risk of rupture in small aneurysms; 3) appropriately triage patients with unruptured very small aneurysms based on morphologic parameters suggested in this study