The pathophysiology of aneurysms

Intracranial aneurysms (IAs) are pathological dilatations of the arterial wall. With widespread utilization of non-invasive imaging, unruptured IAs are diagnosed with increased frequency. Approximately 80–90% are saccular or berry aneurysms. Their pathophysiology is still controversial, but most likely multifactorial and related to interaction between modifiable (smoking and hypertension) and unmodifiable (haemodynamic, genetics, and wall biology) factors. A small group of IAs presents a different aetiology and pathophysiology (traumatic, dissecting, blister, fusiform, and mycotic aneurysms). Although there is no controversy about the indication for treatment of ruptured IAs, management of unruptured IAs is very controversial. While the vast majority of small IAs will remain quiescent for life, a very small number will go on to rupture. Size, location, shape, and other risk factors for aneurysm rupture, must be taken into account when deciding between invasive or conservative management.