United Hospital offers exceptional care for patients with brain aneurysms and vascular malformations. United's comprehensive team of specialist physicians is led by Eric Nussbaum, MD, a neurosurgeon who specializes in aneurysm surgery. Dr. Nussbaum's patients have far lower complication rates than the national average for this type of surgery.

What is a brain aneurysm?

An aneurysm forms when an artery in the brain develops a bulge. This is caused by a weak area in the blood vessel's wall.

The aneurysm can break open and bleed. This is a medical emergency and requires treatment right away.

Location in the brain

Aneurysms occur in the large arteries at the base of the brain. Arteries carry blood pumped by the heart, and the blood flows at high pressure. When a brain aneurysm breaks open (ruptures), blood escapes into space around the brain called the subarachnoid space. The bleeding is called a subarachnoid hemorrhage.

Unruptured aneurysms

Sometimes aneurysms that haven't ruptured, which have no symptoms, are discovered by accident. The neurosurgeon (a doctor who specializes in brain surgery) will consider an unruptured aneurysm very carefully. The risks of preventive treatment will be weighed against the aneurysm's likelihood of bleeding.

Learn more about aneurysms


Brain aneurysms usually have no symptoms until they bleed. Symptoms of a ruptured aneurysm may include:

  • Severe, sudden headache, described as "the worst headache of my life"
  • Neck stiffness
  • Sensitivity to light
  • Nausea and vomiting
  • Loss of consciousness
  • Seizures

Most people with brain aneurysms realize that something is wrong and go to a hospital emergency room.

Why aneurysms are dangerous

Aneurysms that bleed are very serious: half of patients die before reaching a hospital or within the first few days. Of the patients who survive a ruptured aneurysm, half develop a serious disability.

A ruptured brain aneurysm requires treatment because it is likely to bleed again. Each time a brain aneurysm bleeds, the risk of death or disability is high.

Common problems

The possibility of these medical problems reinforces the need for prompt treatment after a ruptured aneurysm.

Extra cerebral spinal fluid builds up in the ventricles of the brain. This fluid moves around the brain and spinal cord at a steady rate. In hydrocephalus, the fluid is blocked and collects in the ventricles, causing swelling and pressure.

To decrease the swelling and pressure, a neurosurgeon may place a drain through the skull and into the ventricle. This drain (called a ventriculostomy) allows the extra cerebral spinal fluid to drain into a collection bag at the bedside. This drain is short-term.

If the fluid and pressure continue to be a problem, the neurosurgeon may place a long-term (permanent) tube.

After an aneurysm, blood spills into the spinal fluid. This exposes the walls of arteries to blood, which can cause them to clamp down (spasm).

The blood vessels inside the brain narrow. This causes decreased blood flow to a region of the brain. This can cause changes such as:

  • inability to move one side of your body
  • difficulty with speech or communication
  • changes in alertness (level of consciousness).

Vasospasm can occur four to 14 days after the bleeding. In severe cases, vasospasm can stop adequate blood flow to the brain, creating a stroke.

A brain aneurysm can cause the body to lose its ability to regulate normal salts (electrolytes) in the blood. The doctor will carefully monitor the electrolyte balance and correct for it.

A seizure is an abnormal electrical discharge in the brain. A seizure may occur after blood from a ruptured brain aneurysm irritates the brain. The patient can lose consciousness and shake violently for seconds or minutes.

Some patients develop problems with the lungs or irregular heart rhythms. Careful monitoring in a neurological intensive care unit is important for this reason.

Reviewed By: Eric Nussbaum, MD, medical director of United's neurovascular neurosurgery program
First Published: 09/17/2013
Last Reviewed: 09/17/2013

Vascular malformations

Specialists in brain aneurysms at United Hospital also care for patients with vascular malformations.

Vascular malformations are abnormal connections between the arteries and veins in the brain. They are also called arteriovenous malformations (AVMs). These usually form before birth.

AVMs are located within the brain. Without the normal channels of vessels to handle blood under high pressure, AVMs can bleed. The bleeding causes a blood clot in the brain, which can lead to death or disability.

Although not as dangerous or common as brain aneurysms, AVMs have significant risks.