Intracranial aneurysm morphology
Size
Shape
Certain shape parameters show stronger correlation with rupture than IA size. Aspect ratio (AR), defined as IA height divided by neck diameter, is the most commonly studied shape parameter. Although most findings affirm its importance, they do not converge on a common threshold value 1) 2) 3) 4) 5).
Calcification
Multilobulation
Presence of a daughter sac
Presence of a small basal outpouching (SBO).
It is important to realize that IA hemodynamics are strongly dependent on the geometry of the aneurysmal sac and its feeding vessel 6) 7) 8).
1)
Beck J, Rohde S, el Beltagy M, Zimmermann M, Berkefeld J, Seifert V, Raabe A. Difference in configuration of ruptured and unruptured intracranial aneurysms determined by biplanar digital subtraction angiography. Acta Neurochir (Wien) 2003;145:861–865.
2)
Raghavan ML, Ma B, Harbaugh RE. Quantified aneurysm shape and rupture risk. J Neurosurg. 2005;102:355–362.
3)
, 8)
Ujiie H, Tachibana H, Hiramatsu O, Hazel AL, Matsumoto T, Ogasawara Y, Nakajima H, Hori T, Takakura K, Kajiya F. Effects of size and shape (aspect ratio) on the hemodynamics of saccular aneurysms: A possible index for surgical treatment of intracranial aneurysms. Neurosurgery. 1999;45:119–130.
4)
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;48:495–503.
5)
Weir B, Amidei C, Kongable G, Findlay JM, Kassell NF, Kelly J, Dai L, Karrison TG. The aspect ratio (dome/neck) of ruptured and unruptured aneurysms. J Neurosurg. 2003;99:447–451. [PubMed]
6)
Hassan T, Timofeev EV, Saito T, Shimizu H, Ezura M, Matsumoto Y, Takayama K, Tominaga T, Takahashi A. A proposed parent vessel geometry-based categorization of saccular intracranial aneurysms: Computational flow dynamics analysis of the risk factors for lesion rupture. J Neurosurg. 2005;103:662–680.
7)
Hoi Y, Meng H, Woodward SH, Bendok BR, Hanel RA, Guterman LR, Hopkins LN. Effects of arterial geometry on aneurysm growth: Three-dimensional computational fluid dynamics study. J Neurosurg. 2004;101:676–681.