Overview
A brain aneurysm (AN-yoo-riz-um) — also known as a cerebral aneurysm or intracranial aneurysm — is a bulge or ballooning in a blood vessel in the brain. An aneurysm often looks like a berry hanging on a stem.
Experts think brain aneurysms form and grow because blood flowing through the blood vessel puts pressure on a weak area of the vessel wall. This can increase the size of the brain aneurysm. If the brain aneurysm leaks or ruptures, it causes bleeding in the brain, known as a hemorrhagic stroke.
Most often, a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. This type of hemorrhagic stroke is called a subarachnoid hemorrhage.
Brain aneurysms are common. But most brain aneurysms aren’t serious, especially if they’re small. Most brain aneurysms don’t rupture. They usually don’t cause symptoms or cause health problems. In many cases, brain aneurysms are found during tests for other conditions.
However, a ruptured aneurysm quickly becomes life-threatening and requires medical treatment right away.
If a brain aneurysm hasn’t ruptured, treatment may be appropriate in some cases. Treatment of an unruptured brain aneurysm may prevent a rupture in the future. Talk with your health care provider to make sure you understand the best options for your specific needs.
Types
- Saccular aneurysm, also known as a berry aneurysm. This type of aneurysm looks like a berry hanging from a vine. It’s a round, blood-filled sac that protrudes from the main artery or one of its branches. It usually forms on arteries at the base of the brain. A berry aneurysm is the most common type of aneurysm.
- Fusiform aneurysm. This type of aneurysm causes bulging on all sides of the artery.
- Mycotic aneurysm. This type of aneurysm is caused by an infection. When an infection affects the arteries in the brain, it can weaken the artery wall. This can cause an aneurysm to form.
Products & Services
- A Book: Mayo Clinic Family Health Book
Symptoms
Most brain aneurysms that haven’t ruptured don’t cause symptoms. This is especially true if they’re small. Brain aneurysms may be found during imaging tests that are done for other conditions.
However, a ruptured aneurysm is a very serious condition, typically causing a severe headache. And if an unruptured aneurysm presses against brain tissue or nerves, it may cause pain and other symptoms.
Ruptured aneurysm
A sudden, severe headache is the key symptom of a ruptured aneurysm. This headache is often described by people as the worst headache they’ve ever experienced.
In addition to a severe headache, symptoms of a ruptured aneurysm can include:
- Nausea and vomiting
- Stiff neck
- Blurred or double vision
- Sensitivity to light
- Seizure
- A drooping eyelid
- Loss of consciousness
- Confusion
‘Leaking’ aneurysm
In some cases, an aneurysm may leak a slight amount of blood. When this happens, a more severe rupture often follows. Leaks may happen days or weeks before a rupture.
Leaking brain aneurysm symptoms may include:
- A sudden, extremely severe headache that may last several days and up to two weeks.
Unruptured aneurysm
An unruptured brain aneurysm may not have any symptoms, especially if it’s small. However, a larger unruptured aneurysm may press on brain tissues and nerves.
Symptoms of an unruptured brain aneurysm may include:
- Pain above and behind one eye.
- A dilated pupil.
- A change in vision or double vision.
- Numbness of one side of the face.
When to see a doctor
Seek immediate medical attention if you develop a:
- Sudden, extremely severe headache
If you’re with someone who complains of a sudden, severe headache or who loses consciousness or has a seizure, call 911 or your local emergency number.
