Pathophysiology and Natural History of Intracranial Aneurysms

Abstract

  The essential pathophysiology of an intracranial aneurysm (IA) involves the degenerative changes that lead to thinning and weakening of the vascular wall. Promoting factors of IA are classified into congenital, environmental, hemodynamic, and acquired factors. Among them, macrophage-mediated inflammation is especially important, and congenital or acquired disturbance of structural integrity of vessel walls is one of the factors promoting IA development. Owing to the development of a rat model for IA rupture, a part of the mechanism of IA rupture, which has not been clarified for a long time, is being elucidated. With respect to the natural history of unruptured IAs, scores predicting the probability of IA rupture based on size, location, and shape of IAs were established according to the results of UCAS Japan and ISUIA, and were utilized in clinical practice. As IAs growing in size during follow-up are at a high risk of rupture, patients with unruptured IA should undergo periodic imaging examinations.