Brain aneurysm risk factors: who is more likely

What a brain aneurysm is

A cerebral aneurysm (or brain aneurysm) is a weak spot on a blood vessel in the brain that fills with blood and bulges out, pressing on the brain and nerves. It can burst open (rupture) and cause bleeding in or around the brain. A ruptured aneurysm is a medical emergency that can cause a stroke, brain damage, coma and even death. But many aneurysms, especially small ones, never rupture or cause symptoms (NINDS).

MedlinePlus notes they are sometimes called berry aneurysms because they are often the size of a small berry (MedlinePlus). NINDS describes three types: saccular (the most common, mostly in adults), fusiform (bulging all the way around a vessel) and mycotic (caused by an infection that weakens a blood vessel) (NINDS).

This page is about aneurysms in the brain. An aneurysm in the large artery in the belly is a different condition; see abdominal aortic aneurysm risk factors.

Risk factors for developing a brain aneurysm

Cerebral aneurysms can happen to anyone at any age. Sometimes babies are born with one, usually because part of a blood vessel wall did not form properly during pregnancy. Having a risk factor does not mean a person will have an aneurysm, and not having one does not mean they won't (NINDS). NINDS lists these risk factors (NINDS):

• Being female. Aneurysms are more common in women than in men, and this risk also seems to increase after menopause.
• Family history. Having a parent, sibling or child with a history of brain aneurysms can increase risk.
• Age. Aneurysms are most common in adults between ages 30 and 60.
• Health conditions that may damage, weaken or put extra stress on blood vessels: high blood pressure, diabetes (linked to fusiform aneurysms), high cholesterol, polycystic kidney disease and connective tissue disorders.
• Lifestyle factors: cigarette smoking (see our quit smoking help check) and using substances such as cocaine or amphetamines.
• Less common risk factors: blood vessel infections caused by injecting drugs, head trauma and injuries, and brain tumors.

What makes a rupture more likely

Not all cerebral aneurysms rupture. Besides high blood pressure and smoking, NINDS names these factors that affect the risk of rupture (NINDS):

• Growth: aneurysms that get bigger, even if they start small, are most likely to rupture.
• Size: in general, bigger aneurysms are more likely to rupture than smaller ones. NINDS calls an aneurysm small if it is under 10 millimeters, large at 11 to 25 millimeters and giant above 25 millimeters.
• Previous ruptures: a person who already had a rupture or a "warning" bleed is more likely to have another one.
• Location: aneurysms in certain parts of the brain, such as toward the back, are more likely to rupture than others.

Symptoms

Most brain aneurysms produce no symptoms until they become large, begin to leak blood or burst (MedlinePlus). A large aneurysm that is growing may press on brain tissue and nerves and cause pain above and behind the eye, numbness, weakness, paralysis on one side of the face, one pupil larger than the other, or changes in eyesight such as double vision (NINDS). MedlinePlus also lists a droopy eyelid (MedlinePlus).

A rupture causes a sudden, severe headache that some people describe as the worst headache of their life. It may also cause double vision, nausea, vomiting, a stiff neck, sensitivity to light, seizures, passing out or becoming unconscious, and cardiac arrest (NINDS). In rare cases an aneurysm leaks a small amount of blood, causing a "warning" headache days or weeks before a major rupture (NINDS).

After a rupture, some people develop delayed cerebral ischemia, when the brain does not get enough blood. It can happen a few days or up to two weeks after the bleeding and may cause stroke-like symptoms (NINDS).

Diagnosis and treatment

Many aneurysms are found only after they rupture, or when a doctor orders a brain scan for another reason. Tests include CT scans, cerebral angiography, MRI and spinal fluid analysis from a spinal tap (NINDS).

Not all aneurysms need treatment. A doctor weighs the chance of rupture with a person's age, health and family history, and may recommend monitoring very small unruptured aneurysms that are unlikely to rupture. Treatments include surgical clipping and endovascular treatments such as coils and flow diversion (NINDS). Treatment depends on the size and location of the aneurysm, whether it is infected and whether it has burst (MedlinePlus).

People with unruptured aneurysms can lower their risk of a rupture by managing conditions such as high blood pressure and avoiding smoking and substances such as cocaine (NINDS).

A tear in the wall of the aorta, the main artery that runs from the heart through the chest and belly, is a different condition (MedlinePlus); see aortic dissection risk factors.

Common questions

Do brain aneurysms run in families?

Family history is a risk factor: having a parent, sibling or child with a history of brain aneurysms can increase risk (NINDS).

Are women more likely to get brain aneurysms?

Yes. NINDS says aneurysms are more common in women than in men, and the risk seems to increase after menopause (NINDS).

Does every brain aneurysm burst?

No. Many aneurysms, especially small ones, never rupture or cause symptoms. Growth, size, a previous rupture and location affect the risk (NINDS).