Presence of vasa vasorum in human intracranial aneurysms

Objectives: Vasa vasorum is associated with the pathogenesis of various cerebrovascular diseases, but its presence in intracranial aneurysms (IA) and its ability to act as a predicting factor of IA rupture remain unrevealed.

Methods: Histological investigation was performed for 3 middle meningeal arteries and 25 human IAs that were sequentially collected from 2017 to 2019. Relevant medical information was collected from the hospital information and imaging system. Fisher's exact tests and Student's t tests were performed to identify the histological and clinical differences between aneurysms with and without vasa vasorum.

Results: Vasa vasorum were present in 14/25 (56%) aneurysm samples. They were detected at a similar frequency in male patients (4/9, 44.4%) and (10/16, 62.5%) female patients. Patients with vasa vasorum present aneurysms (47.07 ± 3.668 years, n = 14) or vasa vasorum absent aneurysms (50.27 ± 2.289 years, n = 11) did not differ in age (p = 0.49). True aneurysms and pseudoaneurysms also shared a similar rate of vasa vasorum presence (10/16, 62.5% in true aneurysms vs 4/9, 44.4% in pseudoaneurysms). The average size of aneurysms with vasa vasorum varied from 21.70 to 3.00 mm, and no statistical difference in size was detected when comparing aneurysms with and without vasa vasorum (p = 0.71). The vasa vasorum in almost all IAs had uniform vascular trajectory with occasional exceptions. The presence of vasa vasorum appears to be tightly associated with important histopathological changes of myointimal hyperplasia and increased immune cell infiltration in IAs (both p value < 0.05), though it does not appear to be indicative of IA rupture or other rupture-related histological degenerations (all p values > 0.05).

Conclusions: The presence of vasa vasorum is common in IAs. While it is associated with aneurysm wall remodeling and robust inflammatory cell infiltration, our results indicate that it is not a single specific marker of rupture-prone aneurysms.