Cerebral Aneurysm

Following is a brief overview of what aneurysms are, how they may affect individuals and families who have been diagnosed with aneurysms and what can be done about them. In addition, this page will provide you with the necessary resources to obtain further information about aneurysms and the experts in this centre who will be able to work with you and help you or someone you know decide what can and should be done to treat this disease.

Presentation & Diagnosis

A cerebral aneurysm, an abnormal dilation or ballooning of a brain artery, can be discovered in several ways. The abnormal dilated wall of aneurysms is weaker than the normal artery wall and aneurysm rupture is one of the more common and unfortunate presentations of cerebral aneurysms. When a cerebral aneurysm ruptures, it typically bleeds into the area surrounding the brain (subarachnoid space) to cause a subarachnoid haemorrhage (SAH). This type of haemorrhage usually causes a sudden and severe headache and may also cause nausea/vomiting, problems with vision, neck stiffness, loss of consciousness, seizures, and even coma or death. Subarachnoid haemorrhage can cause the development of vasospasm which is abnormal constriction of arteries in the brain usually occurring a week or two after surgery. Vasospasm can cause strokes or other neurological damage, often more severe than the original haemorrhage. Less commonly, an aneurysm can rupture and bleed into the brain itself (intracerebral haemorrhage) which can produce a variety of symptoms depending of the size and location of the haemorrhage.

Unruptured cerebral aneurysms may be discovered when they cause neurological symptoms which depend on the location and size of the aneurysm but for example can include headaches, double vision, and trouble walking. Sometimes aneurysms are also found when a head CT or MRI scan, or angiogram is performed for some other reason.

The diagnosis of a cerebral aneurysm is usually confirmed with an angiogram, a radiological picture of the blood vessels in the brain made by taking x-rays of the head after giving an injection of a contrast agent (mainly water and iodine salts) into the blood vessels. Recent advancements in CT and MRI scanning allow these techniques to also help diagnose aneurysms, but an angiogram usually provides the most detail of an aneurysm’s size and location.


For unruptured aneurysms, the goal of treatment is to prevent aneurysm rupture or growth. For ruptured aneurysms, the goal of treatment is to prevent further bleeding (“rebleeding”) and to allow maximal therapy to prevent or limit vasospasm which is limited until the aneurysm is treated.


Surgical treatment for cerebral aneurysms provides direct and effective treatment for most aneurysms. Aneurysm surgery usually involves placing a small metallic clip across the base of the aneurysm (often called the aneurysm “neck”). In doing so, the weak abnormal aneurysm wall is protected from blood flow thus the risk of rupture is eliminated. At the same time, the normal artery wall is reconstructed to maintain blood flow to the brain. The type of operation is determined by the size and location of the aneurysm(s). The timing of surgery is based on many factors but, following aneurysm rupture, early surgery is favoured for most patients because once the aneurysm is treated (“clipped”) maximal therapy to prevent or limit vasospasm can be given.


Endovascular treatments for cerebral aneurysms have developed in recent years and can provide partial or complete treatment of many aneurysms. These treatments typically involve threading a catheter from an artery in the leg up to the aneurysm and under x-ray guidance placing a metal coil into the aneurysm. After applying an electric current, the blood in the aneurysm clots and can thereby fill the aneurysm. Other techniques to fill an aneurysm include injected biological glue materials or sialastic balloons. Endovascular techniques are still developing but have shown utility in treating certain aneurysms which are not suited to surgery as determined by the neurosurgeon.

Common Questions

What causes cerebral aneurysms?
Cerebral aneurysms were once thought to be a congenital (from birth) abnormality. While this may be true in some cases, studies have shown that aneurysms can be caused by a number of factors. Very often, aneurysms develop from a weakening in the structural layer of an artery which allows the growth of an aneurysm. High blood pressure (hypertension) and atherosclerosis (lipid build up in the artery wall) can promote aneurysm growth and rupture. Certain infections in the blood can cause a special kind of aneurysm called a mycotic aneurysm. Although we have an understanding of some of the factors which cause aneurysms, it is usually not possible to determine a single cause for a given patient’s aneurysm.

Can someone have more than one aneurysm?
About 20% of patients with cerebral aneurysms have more than one aneurysm. Patients with multiple aneurysms can have the other aneurysm(s) near or far from the original aneurysm, often at a similar location on the opposite side of the head (“mirror” aneurysm). The decision whether and when to treat multiple aneurysms are based on many factors and are individualized for each patient.

Are cerebral aneurysms hereditary?
There has been several studies demonstrating that some cerebral aneurysms (perhaps 10%) can have a genetic component. Although the nature of hereditary aneurysms is not fully understood, several centres are actively studying this area. Cerebral aneurysm patients who have current or past relatives with known or suspected cerebral aneurysms are encouraged to contact us.

Who should I contact?
Your family doctor will refer you to a neurosurgeon.


Abnormal bulging or dilation (often like a balloon) of a blood vessel, usually an artery. A cerebral aneurysm is an aneurysm of a blood vessel in the brain.

A radiological picture of the blood vessels (arteries and veins) which involves taking x-ray pictures after an injection of contrast material (made of water and iodine salts) usually via a catheter inserted into a blood vessel in the leg. When looking specifically at the arteries, it is also called an arteriogram.

Intracerebral Haemorrhage (ICH):
Abnormal bleeding into the brain which can be caused by hypertension (high blood pressure) or a ruptured aneurysm or arteriovenous malformation (AVM).

Subarachnoid Haemorrhage (SAH):
Abnormal bleeding into the space closely surrounding the brain.Stroke:
Brain injury usually due to not enough blood flow to an area of brain (ischemic stroke) or abnormal bleeding into the brain (hemorrhagic stroke).

Abnormal constriction of arteries which can occur following a ruptured aneurysm (subarachnoid haemorrhage).