A ruptured brain aneurysm is a medical emergency. Without immediate treatment, it may lead to coma or death.

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A cerebral aneurysm, also called a brain aneurysm, can form anywhere in the brain. They are most common in the arteries around the base of the skull.

A small brain aneurysm may not cause symptoms. The risks increase when an aneurysm ruptures.

Here’s what happens when a brain aneurysm ruptures, how it may lead to a coma, and what a person’s outlook may be after this medical event.

Learn more about brain aneurysms.

An aneurysm forms when there’s weakness in a blood vessel on the brain. This blood vessel enlarges, making it prone to rupturing.

Aneurysms develop with age, particularly after age 40, from pressure at points of the arteries. As they grow, they weaken.

Aneurysms may develop spontaneously or from infection, drug use, or head injury. In some people, aneurysms may be related to conditions like:

Some people experience a coma after a ruptured aneurysm due to the loss of blood flow and oxygen to the brain.

Ruptured aneurysms can cause hemorrhagic stroke. This happens when blood from the rupture enters the area between the brain and the skull, called a subarachnoid hemorrhage, or in the brain tissues, called an intracerebral hemorrhage. A stroke causes an interruption of blood flow and oxygen to the brain.

Doctors use a scale called the Hunt and Hess grading system to determine the severity of a ruptured aneurysm. People with mild effects from a rupture may only experience a mild headache (grade 1). People with the most severe effects may experience coma (grade 5).

The more bleeding, the higher the risk of adverse outcomes.

Getting immediate medical help may prevent a ruptured aneurysm from leading to a coma.

Aneurysm symptoms

A small, unruptured aneurysm may not cause symptoms.

As it grows, you may experience:

  • headaches
  • pain at the site of the aneurysm
  • pressure
  • vision issues
  • numbness or weakness in the arms and legs
  • difficulty with memory and speech
  • seizures

A ruptured aneurysm may cause:

Coma symptoms

A coma is an extended state of unconsciousness. It can last 2–4 weeks.

Symptoms of coma may include:

  • closed eyes (appearing to be asleep)
  • no response to stimuli (cannot be woken up)
  • irregular breathing
  • pupillary changes

Doctors can detect an aneurysm through:

  • Diagnostic cerebral angiogram: During a diagnostic cerebral angiogram, you lie flat on an X-ray table. Contrast dye is injected through a catheter that’s inserted into your groin and travels up to your neck. The contrast dye allows the aneurysm to show up on the scan.
  • Computed tomographic angiography (CTA): During a CTA, you go into a CT scan machine. To make the aneurysm show on the scan, a clinician injects contrast dye into a vein.
  • Magnetic resonance angiography (MRA): During an MRA, you go into an MRI scan machine. A clinician takes images of the blood vessels in the brain to look for the aneurysm.
  • Lumbar puncture: During a lumbar puncture, a clinician collects a sample of cerebrospinal fluid (CSF). They specifically look for red blood cells and bilirubin, which may indicate a hemorrhage.

Doctors diagnose a coma by checking a person’s reflexes, response to stimuli, and other signs of awareness.

The Glasgow Coma Scale can also help diagnose a coma. This scale evaluates things like eye opening, verbal responses, and voluntary movements. People who are in a coma typically score a total of 8 or lower in these areas. The lower the score, the more severe the brain injury.

Treatment involves treating the condition that caused the coma. In this case, it means treating the ruptured aneurysm and hemorrhage or stroke.


A medication called nimodipine can treat ruptured aneurysms. It’s a calcium-channel blocker that reduces the risk of cerebral ischemia, or interruption of the blood supply to the brain.

A doctor can also surgically repair the brain aneurysm to stop the bleeding by clipping or coiling the aneurysm.


Healthcare staff will monitor vital signs and give intravenous fluids and medications as needed. The person in a coma may receive supplemental oxygen or breathing support via a ventilator. Staff will also insert a urinary catheter to drain the bladder.

The risk of death is around 40% after a ruptured aneurysm alone, and is 25% in the first 24 hours. Even if the aneurysm is treated, there’s a 66% chance a person will experience brain injury in some form.

For people who have experienced a deep coma (defined as grade 5 on the Hunt and Hess scale) after a ruptured aneurysm, the survival rate is 10%.

If I have one aneurysm, am I at risk of having another?

Yes. There’s a 20% risk of developing additional aneurysms if you have already experienced one.

Can treating a ruptured aneurysm reverse brain injury?

No. Prompt treatment is important to stop the bleeding and prevent severe brain injury. However, once permanent brain injury occurs, it cannot be reversed.

What other complications are common with a ruptured aneurysm?

Other complications may include:

  • vasospasm, which is irritation and contraction of the blood vessels in the brain
  • hydrocephalus, which is a buildup of fluid on the brain
  • trouble breathing
  • infection

If you suspect a brain aneurysm rupture, seek emergency medical attention.

When bleeding interrupts the blood and oxygen supply to the brain, a person may experience anything from headache to brain injury to coma. Treating the aneurysm may improve a person’s outcome.

If you know you have an aneurysm, talk with your doctor about reducing your risk of rupture. This may include lowering your blood pressure, quitting smoking, and avoiding stimulant drugs.