Abstract
The rupture risk of unruptured intracranial aneurysms is known to be dependent on the size of the aneurysm. However, the association of morphological characteristics with ruptured aneurysms has not been established in a systematic and location specific manner for the most common aneurysm locations. We evaluated posterior communicating artery (PCoA) aneurysms for morphological parameters associated with aneurysm rupture in that location. CT angiograms were evaluated to generate 3-D models of the aneurysms and surrounding vasculature. Univariate and multivariate analyses were performed to evaluate morphological parameters including aneurysm volume, aspect ratio, size ratio, distance to ICA bifurcation, aneurysm angle, vessel angles, flow angles, and vessel-to-vessel angles. From 2005–2012, 148 PCoA aneurysms were treated in a single institution. Preoperative CTAs from 63 patients (40 ruptured, 23 unruptured) were available and analyzed. Multivariate logistic regression revealed that smaller volume (p = 0.011), larger aneurysm neck diameter (0.048), and shorter ICA bifurcation to aneurysm distance (p = 0.005) were the most strongly associated with aneurysm rupture after adjusting for all other clinical and morphological variables. Multivariate subgroup analysis for patients with visualized PCoA demonstrated that larger neck diameter (p = 0.018) and shorter ICA bifurcation to aneurysm distance (p = 0.011) were significantly associated with rupture. Intracerebral hemorrhage was associated with smaller volume, larger maximum height, and smaller aneurysm angle, in addition to lateral projection, male sex, and lack of hypertension. We found that shorter ICA bifurcation to aneurysm distance is significantly associated with PCoA aneurysm rupture. This is a new physically intuitive parameter that can be measured easily and therefore be readily applied in clinical practice to aid in the evaluation of patients with PCoA aneurysms.
Highlights
The guidelines for management of unruptured intracranial aneurysms remains one-dimensional even as more and more unruptured aneurysms undergo treatment [1]
Ruptured aneurysms were associated shorter distance to ICA bifurcation in a relationship that approached significance (11.3 mm unruptured versus 10.4 mm ruptured, p = 0.076). (Table 2) Rupture was associated with larger ICA1 to ICA2 angle, and ICA1 to posterior communicating artery (PCoA) angle but these trends were not statistically significant
PCoA aneurysms with lateral projection were more associated with rupture, and this relationship approached significance (30% of unruptured vs 55% of ruptured, p = 0.052)
Summary
The guidelines for management of unruptured intracranial aneurysms remains one-dimensional even as more and more unruptured aneurysms undergo treatment [1]. A recent large prospective natural history study of unruptured aneurysms conducted by the Unruptured Cerebral Aneurysm Study (UCAS) of Japan has underscored the importance of size, and the location and morphology of the aneurysm in predicting rupture risk [6]. Several groups including our own have begun to study contribution of morphological characteristics to the treatment decision of unruptured aneurysms in a systematic and location specific manner. Looking at aneurysms in a location specific manner, our group found that aspect ratio, flow angle, and parent-daughter to be highly associated with middle cerebral artery aneurysm rupture [10]. Matsukawa et al recently reported that rupture of anterior communicating artery aneurysms was associated with anterior dome projection, the presence of blebs, and size $5 mm [11]
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