Intracranial aneurysm growth: consistency of morphological changes

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>Previous studies have shown a relation between growth and rupture of intracranial aneurysms. Additionally, several morphological characteristics are frequently measured to estimate rupture risk. Little is known about how the rupture risk is associated with morphological characteristic changes during growth. The aim of this study was to provide insights into how morphological characteristics, associated with rupture, change during an aneurysm’s growth.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>The authors retrospectively identified patients with longitudinal MRA images of unruptured growing aneurysms. The MRA images had an in-plane resolution of 0.2–0.5 mm and a slice thickness of 0.2–0.75 mm. Therefore, growth was defined as an increase of at least 0.5 mm in two directions or 1 mm in one direction. Using the MRA images, the authors semiautomatically segmented the aneurysm and the perianeurysmal vasculature. Twelve morphological characteristics were automatically measured. These characteristics were related to size (diameter, height, width, neck diameter, volume, surface area, aspect ratio, height-width ratio, and bottleneck factor) and shape (ellipticity index, nonsphericity index, and undulation index) of the aneurysm. Morphological characteristics before and after growth were compared using the Wilcoxon signed-rank test.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>The authors included 31 patients with 38 growing aneurysms. The aneurysms’ growth was detected after a mean of 218 weeks (range 23–567 weeks). A significant increase was seen in all size-related characteristics, and the bottleneck factor also significantly increased (from a median of 1.00 [IQR 0.85–1.04] to 1.03 [IQR 0.93–1.18]), while the ellipticity index decreased (from a median of 0.26 [IQR 0.25–0.28] to 0.25 [IQR 0.24–0.26]). The changes in size ratios and shape indices varied largely among patients. Larger aneurysms more often showed an increase in shape ratios.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>Although aneurysm growth, size-related characteristics, bottleneck factor, and ellipticity index changed significantly during growth, most size ratios and shape indices showed inconsistent changes among aneurysms. This suggests that, for an accurate rupture prediction, morphological parameters need to be reassessed after growth.</jats:p></jats:sec>

Multimodal validation of focal enhancement in intracranial aneurysms as a surrogate marker for aneurysm instability

“…Moreover, numerous morphological parameters including size ratio, undulation index, nonsphericity index, ellipticity index, aneurysm angle, aneurysm volume, neck size. and aspect ratio have been associated with aneurysm rupture [ 22 – 24 ].…”

A Volumetric Metric for Monitoring Intracranial Aneurysms: Repeatability and Growth Criteria in a Longitudinal MR Imaging Study

“…8,[21][22][23][24] Furthermore, most previous studies used only 2 time points (the first and the last) to evaluate aneurysm growth, thus excluding important information on the growth trajectory in the intervening periods. 3,7,16,25 Using such datasets, most studies assume that aneurysm growth is linear and steady, though clinical observation or even proposed growth models 3,16 cause skepticism about this assumption. In this study, we included the often-neglected intermediate events and more sensitively identified a higher percentage of growing aneurysms (32%) than in previous studies (4%$ 18%).…”

Luminal enhancement in intracranial aneurysms: fact or feature?—A quantitative multimodal flow analysis

“…Previous studies have identified numerous factors that are associated and correlated with a high risk of rupture such as morphological parameters (e.g., size and shape) [ 4 , 5 ] and flow characteristics [ 6 ].…”