Diseases and Surgical Procedures

Brain Aneurysm Basics

Being diagnosed with a brain aneurysm is frightening. Having survived a ruptured aneurysm is a very difficult experience to have gone through and can be extremely unsettling. Gathering information about your condition can help ease this fear, help begin the healing process, and help bring a sense of comfort and support during a trying time.

Take the first step by reading the information below. Then, follow the links to learn more.

What is a brain aneurysm?

A brain aneurysm is a weak bulging spot on the wall of a brain artery very much like a thin balloon or weak spot on an inner tube. Aneurysms form silently from wear and tear on the arteries, and sometimes can form from injury, infection, or inherited tendency.

What are the two types of aneurysms?

Saccular Aneusysm

  • Most common type of aneurysm
  • Also known as a “berry” aneurysm because of its shape
  • Has a neck and stem

  • Less common type of aneurysm
  • An out-pouching of an arterial wall on both sides of the artery
  • Does not have a stem

Factors doctors and researchers believe contribute to the formation of brain aneurysms:

  • Smoking
  • Hypertension
  • Traumatic Head Injury
  • Use of Alcohol
  • Use of Oral Contraceptives
  • Family History of Brain Aneurysms
  • Other Inherited Disorders: Ehler’s Syndrome, Polycystic Kidney Disease, and Marfan’s Syndrome

An aneurysm is often diagnosed using a variety of imaging equipment. Whether someone was brought to the hospital unconscious from a rupture or is waiting to undergo treatment for an unruptured aneurysm, similar detection methods are used to pinpoint the location, size, type, and any other characteristics of the aneurysm that will help the doctors make the best decisions about how to move forward.

Detection Methods

CT Scan (Computed Tomography)

This scan takes a picture of your brain. It is a fast and painless test, which requires you to lie on your back, very still, while you are pushed into a large, tubular machine that creates the images. This test shows whether any blood has leaked around or into the brain.

CTA (Computed Tomographic Angiography)

In some cases, doctors may choose to do a CT angiography. This test combines a regular CT scan with a contrast dye injected into a vein. Once the dye is injected into a vein, it travels to the brain arteries, and images are created using a CT scan. These images are more enhanced, because it will show exactly how fluid (blood or dye) is flowing into your brain arteries, alerting doctors to a potential aneurysm or rupture.

MRI (Magnetic Resonance Imaging)

An MRI is a safe, painless diagnostic scan that examines various areas of your body, in this case, your head. Through the use of a large doughnut-shaped magnet and a computer, magnetic signals are seen through a computer as radio waves. The computer is able to transform these radio waves into images. An MRI helps locate the aneurysm.

MRA (Magnetic Resonance Angiography)

This scan combines a regular MRI with the contrast dye, which is injected into a major vein. Like the CTA, this dye travels to the brain arteries, and images are created using an MRI. This creates a more enhanced image.

Angiogram (Arteriogram)

This test allows doctors to see the size, shape, and location of the aneurysm, as well as reveal any bleeding or vasospasm. A small incision is made on one side, or both sides, of your groin after it is locally numbed and prepped. Then, a thin tube (catheter) is threaded through arteries from the groin to the neck. A contrast dye is injected and travels to the brain arteries, X-rays are taken, showing all your arteries and any abnormalities, such as an aneurysm. There are risks involved, which will be explained to you and/or your family prior to the procedure.

Not all brain aneurysms rupture. Doctors are now able to detect unruptured brain aneurysms with an increased frequency. An unruptured brain aneurysm may or may not cause symptoms. Unruptured aneurysms are no less frightening or life altering, but require different diagnostic questions and potential treatments.

Things doctors consider in deciding whether or not to treat an unruptured aneurysm:

  • Risk of Hemorrhage—Is it probable or not that the aneurysm will rupture?
  • Size and Location
  • Age and Health of Patient
  • Family History—Is there a family history? Have any of those aneurysms ruptured?
  • Surgical Risks

If the unruptured aneurysm is treated, usually the recovery period is shorter for survivors of unruptured brain aneurysm treatment than people who had ruptured brain aneurysms. Although, survivors of unruptured brain aneurysm treatment may suffer many of the same physical and emotional symptoms as a survivor of a rupture, they will have a shorter hospital stay, require less rehabilitative therapy, and return to work more quickly.

Subarachnoid Hemorrhage

Stabbing pain in my head,
I need to lie down and go to bed.
Please make it stop.
This pain, this pop!
This ringing in my ears,
These stinging tears and tears.
Call 911, that’s 9-1-1!
Please hurry, my life’s just begun,
It’s not even close to being done.

-H. Karp, SAH Survivor

When a brain aneurysm ruptures, it causes bleeding into the compartment surrounding the brain, the subarachnoid space, causing a subarachnoid hemorrhage (SAH). Often the aneurysm heals over, bleeding stops, and the person survives. In more serious cases, the bleeding may cause brain damage with paralysis or coma. In the most severe cases the bleeding leads to death.


50% of those people die within minutes of a massive hemorrhage. Of the 50% who survive, half will suffer delayed death. The remaining survivors, depending upon the level of hemorrhage, usually live with severe long-term deficits.

Once a hemorrhage has occurred, several consequences might develop.

What Happens to the Brain When an Aneurysm Bleeds?

In most cases, after a rupture the bleeding quickly stops. However, if leaked blood touches brain cells, these cells may become damaged. Blood in the cerebrospinal fluid (CSF) increases the pressure on the brain.

Damage to Brain Cells

Blood from an Aneurysm can leak into the CSF (cerebrospinal fluid) in the space around the brain (subarachnoid space). The pool of blood forms a clot. Blood can irritate, damage, or destroy nearby brain cells. This may cause problems with body functions or mental skills.

Fluid Buildup in the Brain

Blood from a torn aneurysm can block CSF circulation. This can lead to fluid buildup and increased pressure on the brain. The open spaces in the brain, called ventricles, may enlarge. This is known as hydrocephalus. It can make a patient lethargic, confused, or incontinent. Fluid may also build up in the brain after surgery. To stop fluid buildup, a drain may be placed in the ventricles. This removes leaked blood and trapped CSF.

Narrowing of Nearby Arteries

The blood sprayed around the base of the brain can also produce a problem called vasospasm. Vasospasm typically develops 5-8 days after the initial hemorrhage. Narrowing of the blood vessels can occur, and at times not enough blood is supplied to the brain and a stroke may result. To treat vasospasm, blood pressure is often elevated with medicines. Certain medications are also given to try to ease vasospasm. Finally, catheters can be introduced inside the artery in an attempt to use balloons or medications delivered to the vessel directly to open up these narrowed vessels. Vasospasm does relax over several days.


Because blood is sprayed around the base of the brain, the possibility of fluid buildup exists, causing hydrocephalus (picture b). The fluid buildup on the brain is often treated with a tube inserted into the fluid-filled space of the brain (the ventricle). The tube is called a ventriculostomy, and often drains into a bag at the patient’s bedside.


The blood sprayed around the base of the brain can also produce a problem called vasospasm. The blood vessels narrow, and at times not enough blood can be supplied to the brain and a stroke may result. To treat vasospasm, blood pressure is often elevated with medicines. Certain medications are also given to try to ease vasospasm. Certain medications are given to ease the threat of vasospasm. This threat lessens over several days.


The blood sprayed around the base of the brain can also produce a problem called vasospasm. The ruptured aneurysms can heal and be treated, depending upon the severity of the rupture, as well as other factors. Click on treatment to learn about the surgical and non-surgical procedures used to treat ruptured aneurysms.


SAH survivors usually have a much longer recovery time than unruptured aneurysm patients, as well as more serious deficits. Symptoms are proportional to the degree of hemorrhage. Patients who are comatose or semi-comatose after a hemorrhage have longer recoveries and have more significant neurocognitive problems as compared to patients with smaller hemorrhages or unruptured aneurysms