Cerebrovascular Center

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Intracranial Aneurysms


An intracranial aneurysm (also called a cerebral aneurysm) is a balloon-like bulge or weakness in the wall of an artery in the brain. As the bulge grows, it becomes thinner and weaker. It can become so thin that the blood pressure within it can cause it to burst or leak. Aneurysms develop due to a weakening in the artery wall and typically occur on larger blood vessels where an artery branches.

Aneurysm (ruptured) »

Aneurysm (unruptured) »

Signs and Symptoms

Most aneurysms are asymptomatic until they rupture. Ruptured aneurysms release blood into the spaces around the brain called a subarachnoid hemorrhage (SAH). Unruptured aneurysms rarely show symptoms until they grow large or press on vital structures.


A patient may live for years or even decades without knowing he or she has an aneurysm. Risk factors for aneurysm formation include; high blood pressure, atherosclerosis (plaque build-up inside the arterial wall) and smoking, so these risk factors should be avoided at all costs. In addition, people with a family history of aneurysms are four times more likely to have aneurysms.



Sometimes the best treatment is to closely monitor and reduce the risk of rupture by quitting smoking and/or controlling high blood pressure. Small, unruptured aneurysms that are not causing symptoms may be observed with annual imaging scans until growth or symptoms necessitate surgery.

Surgical Clipping

One treatment option for an aneurysm is direct surgical clipping. The patient is placed under general anesthesia, and an opening is made in the skull, called a craniotomy. The brain is gently retracted so that the artery with the aneurysm is well visualized. A small, permanent clip is placed across the neck of the aneurysm to block blood flow from entering the aneurysm.

Artery Occlusion and Bypass

If surgical clipping is not possible or the artery is too damaged, the surgeon may completely block the artery with the aneurysm. The blood flow is bypassed or re-routed using a small artery taken from the scalp. This allows the blood flow to be detoured around the artery with the aneurysm. The bypass artery is sewn into place by the surgeon above and below the section of the artery with the aneurysm.

A bypass graft can also be created from a different artery that is re-routed from its normal position, passed through a hole in the skull, and sewn into the place above the aneurysm. This procedure is called a Superficial Temporal Artery – Middle Cerebral Artery bypass, or STA-MCA bypass.

Endovascular Coiling

This type of treatment is performed by a Neuro Interventionalist in the angiography suites. In a coiling procedure, a catheter is inserted into an artery in the groin and passed through the blood vessels to the aneurysm. The doctor guides the catheter through the blood stream while watching a fluoroscopy (X-ray) monitor. Through the catheter, the aneurysm is packed with material, either platinum coils or balloons, that prevent blood flow into the aneurysm. After this procedure, follow-up angiograms are performed periodically to confirm that the aneurysm is still occluded and not growing larger.