Background: Cerebral aneurysm growth is supposed to often precede aneurysm rupture. To predict aneurysm growth for unruptured aneurysms is still difficult by means of recently well-developed commercially available computational fluid dynamic (CFD) software.
Purpose: To detect the possible factor contributing to for the aneurysm growth with our originally developed CFD tool.
Methods: We retrospectively reviewed the aneurysms that were treated between April 2013 and March 2016 at our institute by surgical clipping or endovascular coiling with the reason of its growth (growth group). In contrast, we extracted unruptured aneurysms that had experienced no growth for at least five years (non- growth group). Time of flight (TOF) - magnetic resonance (MR) imaging data of them were converted to the three- dimenstional (3D) vessel geometric data and three hemodynamic indices: stream line (SL), wall shear stress (WSS), oscillatory shear index (OSI), were calculated with lattice Boltzmann method and compared between the two groups.
Results: Six growth aneurysms and 5 non-growth aneurysms were analyzed in this study. In the growth group, mean initial aneurysms size was 4.7mm and increased to 6.2mm after mean follow up of 33.4 months. In the non-growth group, mean aneurysm size was 5.8mm. Analyses of flow dynamics were successfully done in all cases. In all six enlarged aneurysms, WSS was increased temporally at the early diastolic phase on the focal aneurysmal sac where the aneurysms would enlarge in the future (Fig. A,B). Furthermore, in four of them, focal increase in WSS formed crescent-like shape surrounding low WSS (Inset in Fig. A). In contrast, WSS was not increased even at the early diastolic phase in three of five non-enlarged aneurysms. The SL or OSI showed no specific differences between the two groups.
Conclusion: Focal increase of WSS, some of them formed crescent-like shape, at the early diastolic phase may be the possible factor for the aneurysm enlargement in future.