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Do You Know the Basics About Brain Aneurysms?


If your body were a ship, your brain would be the captain. If it were a company, your brain would surely be sitting in the CEO chair.

You get the picture — your brain is in charge.

The brain is the most complex organ in the body. It controls everything: your thinking, senses, movement, and behavior. That’s why it’s so well protected by the skull and a layer of fluid.

The skull and fluid keep your brain safe from a traumatic brain injury (TBI). But that doesn’t mean that serious problems — like a brain aneurysm — can’t pop up within the brain itself.

“A cerebral aneurysm — often referred to as a brain aneurysm — is a weak or thin spot that develops in one of the brain’s arteries,” says Omar Choudhri, MD, neurosurgeon at Penn Medicine. “As blood flows through this weak spot, it puts pressure on the artery wall, which can cause it to balloon or bulge out. This is called a brain aneurysm.”

According to Dr. Choudhri, brain aneurysms can occur anywhere in the brain, but they’re most common at the base of the skull, where your neck meets your head. “Usually, brain aneurysms don’t produce any symptoms until they become large, begin to leak blood, or rupture (burst),” he says. “This can be very dangerous to the surrounding brain tissue.”


Here’s what Dr. Choudhri suggests you know about brain aneurysms — what causes them, warning signs to look out for, how they’re diagnosed and treated, and steps you can take to lower your risk of developing an aneurysm.

What Causes Brain Aneurysms?

Think of the brain like a building. Its arteries are the hallways, and they carry blood around to various “rooms” in your brain. In order to access parts of the brain, those hallways branch off. Where the different hallways connect, the walls tend to be weaker. This is where aneurysms typically occur.

Certain risk factors for brain aneurysms are a result of conditions you have no control over, such as age or genetics. These include:

  • Connective tissue disorders (such as Ehlers-Danlos syndrome): These disorders can weaken artery walls
  • Polycystic kidney disease: A condition that causes cysts to form on the kidneys
  • Arteriovenous malformations: Tangled arteries that disrupt blood flow
  • A family history of brain aneurysms: Having a close (first-degree) family member — such as a parent, child, or sibling — who had a brain aneurysm increases your risk
  • Age: Brain aneurysms are more common after age 40

Less common causes include head trauma, brain tumors, and infections in the walls of the arteries.

There are also a few risk factors that are in your control, such as:

  • Untreated high blood pressure
  • Smoking
  • Drug abuse, especially cocaine or amphetamines, which raise blood pressure

Taking steps to manage these factors, such as lowering your blood pressure or quitting smoking, can help decrease your risk level.

What Are Warning Signs of Brain Aneurysms?

Some aneurysms go undetected and may not cause any symptoms at all, especially if they’re small (less than the size of a pencil eraser). You may not ever know that you have one, or it may be found during an imaging test — such as a magnetic resonance imaging (MRI) — that you are having for a separate medical condition.

Unruptured Brain Aneurysm

Aneurysms typically start to cause symptoms when they are growing or when they are larger in size. This is because as they grow they put pressure on the surrounding nerves and brain tissue. Symptoms of an unruptured brain aneurysm include:

  • Pain above and behind the eye
  • Numbness, weakness, or paralysis on one side of the body
  • A dilated pupil in one eye
  • Changes in vision or double vision
  • A droopy eyelid

Ruptured Brain Aneurysm

All brain aneurysms can potentially rupture, causing blood to spill into the surrounding tissue. This rupture is called a hemorrhage. A rupture can lead to a hemorrhagic stroke (when leaked blood damages the surrounding tissue and cells), brain damage, coma, or even death. About 25% of patients don’t survive the first 24 hours after a brain aneurysm, and another 25% die from complications in the first 6 months of recovery.

Symptoms of a ruptured brain aneurysm include:

  • Sudden, severe headache
  • Double vision
  • Nausea and vomiting
  • Stiff neck
  • Sensitivity to light
  • Seizures
  • Loss of conscious — either briefly or for a longer period of time
  • Cardiac arrest (heart attack)

How Are Brain Aneurysms Diagnosed and Treated?

Most brain aneurysms aren’t detected until they rupture or are found during other medical screenings. If you believe you have an unruptured aneurysm, see your primary care provider or neurologist right away.

Call 911 or go to the emergency room immediately if you experience symptoms of a ruptured brain aneurysm.

There are several tests that can help make a diagnosis, including:

  • Computed tomography (CT): an imaging test that creates an X-ray of the brain
  • Magnetic resonance imagery (MRI): an imaging test that uses radio waves and a magnetic field to create a picture of the brain
  • Cerebral angiography: an imaging test that finds blockages in your arteries using an injected dye
  • Cerebrospinal fluid (CSF) analysis: a test that detects blood in the fluid that protects your brain and spinal cord, usually taken using a spinal tap (removal of spinal fluid using a thin, hollow needle)

Treating a Brain Aneurysm

The best way to treat an aneurysm depends on many factors, including:

  • The size, location, and shape of the aneurysm
  • The risk of the aneurysm rupturing, based on its location and growth rate
  • Your age and overall health
  • Your medical history, including whether you have a family history of aneurysms

Treatment options for both ruptured and unruptured aneurysms involve reducing or cutting off the aneurysm’s blood supply, making it less likely to rupture from the blood’s pressure. These include:

  • Microsurgical clipping: an open surgical procedure that cuts off the aneurysm’s blood supply
  • Platinum coil embolization: an endovascular procedure where coils are inserted through a catheter (thin, hollow tube) into the artery where the aneurysm is located, cutting off its blood supply. This may involve use of adjuncts such as balloons, stents and neck reconstruction devices particularly for wide based aneurysms.
  • Flow diversion: an endovascular procedure where a device — such as a stent (small, flexible mesh tube) — is inserted through a catheter into the artery where the aneurysm is located, reducing blood flow to the aneurysm
  • Intrasaccular Flow Diversion: an endovascular procedure where a mesh device placed inside the aneurysm to occlude it

The Bottom Line About Brain Aneurysms

“An unruptured brain aneurysm may go completely unnoticed — and it may not cause any symptoms in a person’s lifetime. However, if a rupture occurs, it can be life-threatening,” says Dr. Choudhri. “By staying on top of your health by scheduling regular check-ups, addressing risk factors you can control, keeping an eye out for warning signs, and getting help right away if you notice these signs, you can take a proactive role in protecting your health.

For more information about preventing, diagnosing, and treating brain aneurysms, schedule an appointment with a Penn Medicine neurosurgeon by calling 800-789-7366 or request an appointment online.

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