Structural Characteristics of Intracranial Aneurysms

The natural history of unruptured intracranial aneurysms (IAs) is poorly understood. At present, risk factors for aneurysm rupture are limited to demographics and rudimentary anatomic features of the aneurysm. The first sign of aneurysm destabilization and rupture may be subarachnoid hemorrhage, a potentially devastating brain injury with high morbidity and mortality. An emerging body of literature suggests a complex inflammatory cascade likely promotes aneurysm wall remodeling and progressive ballooning of the arterial wall, ultimately terminating in aneurysm rupture. These events likely begin with hemodynamic, flow-related endothelial injury; the injured endothelium stimulates inflammation, including the recruitment and transmigration of inflammatory cells, particularly macrophages. Various proteases are secreted by the inflammatory infiltrate, resulting in degradation of the extracellular matrix and the structural changes unique to IAs. Detailed understanding of these inflammatory processes may result in (1) early identification of patients at high risk for aneurysm rupture, perhaps via arterial wall imaging, and (2) targeted, noninvasive therapies to treat or even prevent cerebral aneurysms.