Unruptured intracranial aneurysm volume change patterns and association with age, sex, location in vascular tree, and common risk factors: a single-centre retrospective study.

Introduction: Unruptured intracranial aneurysms pose a significant clinical and decision-making dilemma. Increase in dome size is one of the crucial indications for treatment. Almost no data exists as to how aneurysms change in size over time.

Material and methods: 102 patients (76 women) who had a total of 501 CT examinations were included in the study. Inclusion criteria were: at least three CT angiography studies, an observation period of at least three years, or bleeding during the follow-up period. In each study, the volume of each aneurysm was measured at least four times by two experienced neuroradiologists with the use of dedicated tools. Collected data was used to obtain numerical volume change models for each aneurysm.

Results: 149 aneurysms were analysed in the study (118 in women) No significant differences in location, size or age of observation were detected between men and women. Median follow-up was 5.64 years (IQR 4.17-7.71) and total aneurysm observation time amounted to 964.59 years. There were 57 branching zone aneurysms (women 46), 44 sidewall aneurysms (women 36), 20 anterior communicating artery aneurysms (women 16), 20 posterior communicating artery aneurysms (women 13), and eight posterior circulation aneurysms (women 7). 78 (52%) aneurysms remained stable (women 59), 24 (16.6%) increased their volume (women 20), and five (3.4%) decreased (women 4). In 42 (28%) cases, we observed non-uniform routes of volume changes over surveillance (women 35). In the last group, analysing the whole period of follow-up, 29 (69%) did not change volume (women 24), 11 (26%) grew (women 10), and two decreased in size (4.8%, women 1). Bifurcation zone aneurysms, lower aspect ratio, lower patient age, and higher initial volume were associated with an increased risk of aneurysm growth. Posterior circulation aneurysms presented the lowest rate of volume increase.

Conclusions: A substantial amount of followed up aneurysms could change volume in a non-uniform way, and an increase in volume may not lead to aneurysm rupture.