1.3 Treatment options for intracranial aneurysms The wide availability and use of noninvasive imaging has increased the frequency of incidental discovery of intracranial aneurysms. There are two broad categories of intracranial aneurysms: those that have ruptured, creating subarachnoid hemorrhage and those that are unruptured. Subarachnoid hemorrhage from aneurysm rupture is a devastating event. It is estimated that about 40% of individuals whose aneurysm has ruptured do not survive the first 24 hours: up to another 25% die from complications within 6 months. Early diagnosis and treatment are important. [27] Aneurysm treatments include medical, surgical and endovascular therapies. Medical therapy involves general supportive measures and prevention of complications for individuals who are in the periprocedural period or are poor surgical candidates and includes: control of hypertension, calcium channel blockers, prevention of seizures and antibiotic therapy for those presenting with infectious aneurysms. In the microsurgical approach, a section of the skull is removed. The brain tissue is then spread apart to reveal the aneurysm and a small metal clip is placed at the base of the aneurysm to block the flow of blood. Alternative microsurgical techniques involve proximal or Hunterian ligation, wrapping of the aneurysm or trapping (i.e., a combination of proximal and distal vessel occlusion). [22] Endovascular therapy (EVT) involves insertion of a catheter into the femoral artery in the patient's leg and navigating it though the vascular system into the head and aneurysm. Once there, several treatment options are available: detachable coils may be deployed within the aneurysm to occlude it from the parent artery blood flow, this may be done alone or by using an adjunctive technique such as balloon remodeling or intracranial stenting of the parent artery. In balloon remodeling, a temporary occlusion balloon is inflated across the neck of the aneurysm while the coils are introduced. The balloon functions to prevent the prolapse of coils into the parent vessel. Although the temporary occlusion balloons provide support for the coils during their introduction, sometimes the coil can prolapse into the parent artery immediately after balloon deflation [28]. Also very wide-necked or irregular shaped aneurysms may lack a neck structure making coil placement difficult or impossible. These aneurysms may have an intracranial stent placed in the parent artery crossing the neck of the aneurysm. The coils are then introduced through the stent in order to help jail them within the aneurysm. Parent vessel occlusion, although not as common as aneurysm coiling is performed mostly on fusiform and acute dissecting arteries and involves the complete occlusion of the parent vessel with coils and sometimes embolic liquid.