Hemodynamic analysis of a thrombosed bleb in an unruptured cerebral aneurysm.

Background: The intricate hemodynamic mechanisms of thrombosis in the bleb and/or dome of cerebral aneurysms remain unresolved. We encountered a unique case where the bleb of an unruptured internal carotid-posterior communicating artery (IC-PC) aneurysm underwent thrombosis over 7 years. Complete spontaneous thrombosis of a bleb in an unruptured cerebral aneurysm has not been previously reported. Therefore, a hemodynamic evaluation using computational fluid dynamics (CFD) analysis was conducted to examine the thrombotic development within the bleb of this aneurysm. Case Description: We observed a case in which thrombosis led to the disappearance of a bleb in the dome of an unruptured IC-PC aneurysm over 7 years. CFD analysis was employed to investigate the hemodynamics of bleb thrombosis and the thrombosed bleb-neck regions of the dome in this IC-PC aneurysm. The reduction and disappearance of the bleb were associated with a decreased flow rate within the bleb, reduced magnitude of wall shear stress (WSSm), a lower WSSm ratio between the bleb and dome, increased vector direction of wall shear stress (WSSv), and discrete streamlines entering the bleb-neck region, resulting in stasis and subsequent thrombosis within the bleb. Seven years later, the dome region corresponding to the thrombosed bleb-neck exhibited localized areas with low WSSm and high WSSv along the dome wall. Conclusion: Hemodynamically, spontaneously thrombosed bleb and thrombosed post-bleb-neck dome walls were characterized by low WSSm and high WSSv. These findings underscore the importance of CFD analysis in predicting thrombotic events in cerebral aneurysms, which can inform better clinical management strategies.