Monitoring of microsurgically and endovascularly treated aneurysms (META): protocol for an international multicentre retrospective cohort study

Intracranial aneurysms (IAs) are abnormal outpouchings or dilations on the main blood vessels supplying the brain. 3% of the general population have IAs and the majority will remain asymptomatic however a proportion will go on to rupture and cause subarachnoid haemorrhage (SAH), which is a condition associated with a significant rate of death and disability. The treatment of both ruptured and unruptured IAs aims to prevent future aneurysm rupture leading to SAH. Historically, the only treatment modality for IAs was a neurosurgical operation called microsurgical clipping but more recently endovascular treatment, whereby the aneurysms can be treated using catheters inserted into the arteries of the groyne or wrist has become the predominant treatment. However, there are very few studies describing the long-term outcomes of microsurgical clipping or endovascular treatment, particularly with respect to the requirement for aneurysm re-treatment or SAH due to rupture of a previously treated aneurysm. The aim of this study is to assess the outcomes following microsurgical clipping and endovascular treatment of a large number of both ruptured and unruptured IA over an extended follow-up period, with a view to providing data that will permit us to optimise the follow-up of patients with IA following treatment.