Introduction: Hemodynamic stresses play an important role in the generation, growth, and rupture of cerebral artery aneurysms. Thin-walled regions (TWR) and atherosclerotic regions (ASR) of the aneurysm dome represent areas of focal weakness that may lead to aneurysm rupture. Our group previously reported on the correlation of Pmax (spatial and temporal maximum pressure) and aneurysm dome TWRs as well as RRTmax (relative residence time) and ASRs in unruptured middle cerebral artery (MCA) aneurysms using computational fluid dynamic (CFD) analyses in a retrospective manner.
Methods: To validate the correlation of Pmax with TWRs and RRTmax with ASRs, unruptured or ruptured MCA aneurysms that underwent microsurgical clip occlusion were analyzed using CFD in a prospective fashion. Using 3D DSA or CTA, Pmax and RRTmax areas were determined with a fluid-flow formula under pulsatile blood flow conditions and the pressure difference (PD) was calculated by subtracting the average pressure (Pave) from Pmax areas and dividing by the aneurysm inlet mean velocity for normalization. TWRs were identified as thin, red, and translucent areas of the aneurysm dome relative to healthy, non-calcified proximal parent vessels, while ASRs were identified as thick, yellow regions. Rupture points were identified by the presence of localized thrombus on the aneurysm dome. Surgical treatment and CFD analyses were performed separately, and the correlation between Pmax and TWRs and RRTmax and ASRs was assessed.
Results: Between January 2016 and July 2016, 12 patients (10 unruptured, 2 ruptured) with MCA aneurysms underwent microsurgical clip occlusion. Based on CFD analyses, Pmax areas were identified in 6 unruptured aneurysms, 5 of which (83.3%; PD=1.24±0.62) were seen to correspond to TWRs during surgery (Figure 1). In addition, RRTmax areas were identified in 9 unruptured aneurysms, 7 of which (77.7%; RRT=5.43±2.00) were seen to correspond to ASRs during surgery. In the 2 ruptured cases, RRTmax (RRT=7.42, 36.67) areas corresponded with the presumed aneurysm rupture point (Figure 2).
Conclusions: Pmax and RRTmax areas may predict degenerative aneurysm walls. These factors may be critical in predicting aneurysm degeneration and ruptured risk, and CFD has the potential for clinical use in the treatment algorithm of cerebral aneurysms.
Patient Care: The results of study aim to describe key features of aneurysm wall morphology using computational fluid dynamic analyses of angiographic data. These data are correlated with intraoperative findings. The results of this study may allow for the early identification of aneurysms at risk of growth and ruptured, so that treatment may be offered in an expedited manner.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Describe the importance of aneurysm wall degenerative in aneurysm growth and rupture.
2) Discuss, in small groups, advances in technology that allow for assessment of the degree of aneurysm wall degeneration using computational flow dynamics.
3) Identify an effective treatment for aneurysms with varying degrees of wall degeneration.