Morphological Differences between Ruptured and Unruptured Basilar Bifurcation Aneurysms

Abstract

Background Aspect ratio (AP), daughter artery ratio (DA), and lateral angle ratio (LA) have been reported in middle cerebral artery bifurcation aneurysms to correlate with rupture status.

Objective To study the differences in AP, DA, LA, and aneurysm orientation between ruptured and unruptured basilar bifurcation aneurysms.

Methods Three-dimensional (3D) angiograms of patients with basilar bifurcation aneurysms were analyzed for AP, DA, and LA. Aneurysm projection was classified as type A if the long axis of aneurysm was along basilar artery and type-B if otherwise.

Results Thirty-one ruptured and 17 unruptured aneurysms were analyzed. The APs were significantly different (p = 0.008), 2.63 ± 1.1 for ruptured aneurysms and 1.7 ± 0.55 for unruptured aneurysms. AP ≥ 1.9 correlated with rupture status with 68% sensitivity and 70% specificity. Type-A configuration was significantly associated with ruptured aneurysms with an odds ratio (OR) of 5.9. LAs were 0.9 ± 0.4 and 1.4 ± 0.8 for ruptured and unruptured aneurysms, respectively, and the difference tended to be significant (p = 0.56). DAs were 1.25 ± 0.22 and 1.21 ± 0.19 for ruptured and unruptured aneurysms without any statistical difference.

Conclusion AP > 1.9, type-A configuration, and lower LA is associated with ruptured basilar bifurcation aneurysms. DA did not differ between ruptured and unruptured aneurysms

Keywords

rupture - aspect ratio - lateral angle ratio - daughter artery ratio - aneurysm

• References

• 1 Wermer MJ, van der Schaaf IC, Algra A, Rinkel GJ. Risk of rupture of unruptured intracranial aneurysms in relation to patient and aneurysm characteristics: an updated meta-analysis. Stroke 2007; 38: 1404-1410
• 2 Shojima M, Oshima M, Takagi K , et al. Magnitude and role of wall shear stress on cerebral aneurysm: computational fluid dynamic study of 20 middle cerebral artery aneurysms. Stroke 2004; 35: 2500-2505
• 3 Qian Y, Takao H, Umezu M, Murayama Y. Risk analysis of unruptured aneurysms using computational fluid dynamics technology: preliminary results. AJNR Am J Neuroradiol 2011; 32: 1948-1955
• 4 Farnoush A, Avolio A, Qian Y. Effect of Bifurcation Angle Configuration and Ratio of Daughter Diameters on Hemodynamics of Bifurcation Aneurysms. AJNR Am J Neuroradiol 2012; 2
• 5 Sadatomo T, Yuki K, Migita K, Taniguchi E, Kodama Y, Kurisu K. Morphological differences between ruptured and unruptured cases in middle cerebral artery aneurysms. Neurosurgery 2008; 62: 602-609 , discussion 602–609
• 6 Baharoglu MI, Lauric A, Gao BL, Malek AM. Identification of a dichotomy in morphological predictors of rupture status between sidewall- and bifurcation-type intracranial aneurysms. J Neurosurg 2012; 116: 871-881
• 7 van der Kolk NM, Algra A, Rinkel GJ. Risk of aneurysm rupture at intracranial arterial bifurcations. Cerebrovasc Dis 2010; 30: 29-35
• 8 Takao H, Murayama Y, Otsuka S , et al. Hemodynamic differences between unruptured and ruptured intracranial aneurysms during observation. Stroke 2012; 43: 1436-1439
• 9 Ingebrigtsen T, Morgan MK, Faulder K, Ingebrigtsen L, Sparr T, Schirmer H. Bifurcation geometry and the presence of cerebral artery aneurysms. J Neurosurg 2004; 101: 108-113
• 10 Ujiie H, Tamano Y, Sasaki K, Hori T. Is the aspect ratio a reliable index for predicting the rupture of a saccular aneurysm?. Neurosurgery 2001; 48: 495-502 , discussion 502–503