Brain Aneurysms: Causes, Symptoms, and Treatment

Medically Reviewed by Zilpah Sheikh, MD on December 06, 2023
Written by Julie Marks
10 min read

A brain aneurysm is a weak spot in the wall of a blood vessel inside the brain that can sometimes burst and cause a subarachnoid hemorrhage. Think of a weak spot in a balloon and how it feels stretched out and thin. A brain aneurysm is like that.

That area of the blood vessel gets worn out from constant flow of blood and bulges out, almost like a bubble. It can grow to the size of a small berry.

Although brain aneurysms sound alarming, most don't cause symptoms or health problems. You can enjoy a long life without ever realizing that you have one. But in rare cases, aneurysms can grow big, leak, or explode. Bleeding in the brain, known as a hemorrhagic stroke, is serious, and you'll need medical care right away.

Aneurysm vs. stroke

Aneurysms and strokes are two very different medical conditions. A stroke happens when a blood vessel in the brain bursts (called a hemorrhagic stroke) or becomes blocked by a clot (called an ischemic stroke). On the other hand, an aneurysm is a bulge that occurs because of a weak artery wall. However, if an aneurysm bursts and bleeds, it may be thought of as a type of a hemorrhagic stroke.

Strokes often strike without warning, while aneurysms can form over a long time. The treatment for each condition is also different. For a stroke, doctors give clot-busting drugs or perform a procedure to remove the clot. If you have an aneurysm, you may need surgery to repair the blood vessel.

There are different kinds of aneurysms, including:

Saccular aneurysms are the most common type of brain aneurysm. They bulge out in a dome shape. They're connected to the artery by a narrow “neck.” A saccular aneurysm is also known as a “berry aneurysm” because it looks like a berry that hangs from a vine.

Fusiform aneurysms aren't as common as saccular aneurysms. They don't pouch out in a dome shape. Instead, they make a widened spot in the blood vessel.This type of an aneurysm causes all sides of the artery to bulge.

Mycotic aneurysms are caused by a bacterial, fungal, or viral infection that affects arteries in the brain. The infection can cause the artery wall to weaken. This type of an aneurysm is rare.

Aneurysms come in different sizes:

  • Small aneurysms are smaller than 11 millimeters (mm) in diameter, which is about the size of a pencil eraser.

  • Large aneurysms measure 11-25 mm in diameter, which is about the size of a dime.

  • Giant aneurysms are larger than 25 mm in diameter, which is more than the width of a quarter.

How fast do brain aneurysms grow?

Aneurysms grow at different rates. Some never grow at all. Others may take many years to develop. And some grow very quickly, in about a week's time.

The type of symptom you have from a brain aneurysm depends on whether it ruptures.

Ruptured brain aneurysm symptoms

You need emergency care if you suddenly get an intensely painful headache, lose consciousness, or have any of these other symptoms of an aneurysm rupture:

  • Intense headache that comes on suddenly
  • Loss of consciousness
  • Nausea and vomiting
  • Drowsiness
  • Loss of balance in things like walking and normal coordination
  • Stiff neck
  • Dilated pupils
  • Sensitivity to light
  • Sudden blurred or double vision
  • Drooping eyelid
  • Confusion or trouble with mental awareness
  • Cardiac arrest (when the heart suddenly stops beating)
  • Seizure

Although brain aneurysms usually don't show symptoms, they can press on the brain and nerves as they get bigger.

Unruptured brain aneurysm symptoms

See a doctor at once if you're having a new headache or pain above or behind your eye. Call 911. Other symptoms of an unruptured aneurysm are:

  • Dilated pupils
  • Blurred or double vision
  • Drooping eyelid
  • A hard time speaking
  • Weakness and numbness on one or both sides of your face
  • Paralysis on one side of your face

A sudden and intense headache can also be a sign you have a leaking aneurysm (sentinel bleed). This can be a warning sign you'll soon have a full rupture.

It's possible to have a problem with blood vessels at birth that may lead to brain aneurysms.

Some inherited conditions that are linked to brain aneurysms are:

  • Autosomal dominant polycystic kidney disease. This condition causes small fluid-filled cysts to form on the kidneys.
  • Neurofibromatosis type 1. It causes changes in skin color and tumors to grow along nerves in the skin, brain, and other areas of the body.
  • Marfan syndrome. People with this disorder are typically tall with very long arms, fingers, legs, and toes.
  • Multiple endocrine neoplasia type 1. It causes tumors to grow in the endocrine glands, small intestine, and stomach.
  • Pseudoxanthoma elasticum. With this disorder, calcium and other minerals build up in parts of connective tissue in the body.
  • Hereditary hemorrhagic telangiectasia. It causes a tangle of blood vessels, called arteriovenous malformations (AVMs), to develop between arteries and veins.
  • Ehlers-Danlos syndrome types II and IV. These conditions affect the connective tissue that supports the skin, bones, blood vessels, and other organs.

Aneurysms tend to form at the fork of blood vessels, places where they branch off, because those sections tend to be weaker. They are most commonly found at the base of the brain.

If your brain aneurysm ruptures or leaks and causes a hemorrhagic stroke, you'll need medical treatment right away. This is rare but can be life-threatening.

Your doctor usually won't know why your brain aneurysm ruptured. But experts know a few reasons that could heighten your risk of bleeding:

High blood pressure. This is the most common factor that leads to a ruptured brain aneurysm.

Heavy lifting or straining. Your brain aneurysm may rupture because of pressure from lifting or straining.

Strong emotions. If you're very upset or angry, this can raise your blood pressure and lead to a ruptured aneurysm.

Medications. Blood thinners including warfarin (Coumadin, Jantoven) and other medicines or prescription drugs, such as diet pills like ephedrine and amphetamines, can cause an aneurysm to bleed.

Illegal drugs. Drugs, like cocaine, can cause your aneurysm to rupture.

Brain aneurysms usually develop as people age, becoming more common after 40. Women tend to have higher rates of aneurysms than men. Smoking and high blood pressure are the things that put you at the most risk of having a brain aneurysm. But several other things in your medical history also raise your odds.

Medical history

Things in your medical history that can play a role include:

  • High blood pressure
  • Atherosclerosis, a disease in which fat builds up inside the walls of your arteries (blood vessels that deliver oxygen-rich blood throughout your body)
  • Diseases affecting your blood or blood vessels:
  • Injury or trauma to your head
  • Infection
  • Cancer or tumors in your head and neck
  • Abnormalities at birth, such as tangled blood vessels in your brain, abnormally narrow aorta (coarctation of the aorta), or cerebral AVM (brain AVM)
  • Family history of brain aneurysms
  • Smoking
  • Alcohol use, especially binge drinking
  • Drug abuse, of stimulants like cocaine or amphetamines.

Rarely, kids under 18 can have a brain aneurysm. Boys are eight times more likely to get them than girls. Of the few cases in children, about 20% are “giant” aneurysms (larger than 2.5 centimeters).

Aneurysms in kids can come on for no reason. But they're also sometimes related to:

  • Head trauma
  • Connective tissue disorders
  • Infection
  • Genetic disorders
  • Family history

Several types of scans and tests can be used to figure out whether you have a brain aneurysm. They include:

CT scan: This exam creates images of your brain. You will lie on a table that slides into a CT scanner. A technician will inject a contrast dye into one of your veins to make it easier to see the blood flow and spot aneurysms in your brain.

MRI: This exam is similar in that you lie on a table that slides into a scanner. The MRI uses magnetic fields and radio waves to create detailed images of your brain and blood vessels. MRIs and CT scans can detect aneurysms larger than 3-5 mm.

The following tests are more invasive than CT or MRI scans. But they could give you and your doctors a more complete picture of what's going on:

Angiogram: This test, considered the most reliable way to detect aneurysms, shows the weak spots in your blood vessels. During the test, you lie on an X-ray table, and you will be given something to numb any pain. Your doctor will insert a small flexible tube through a blood vessel in the leg. They'll guide that tube, called a catheter, into the blood vessels in your neck that reach the brain. Then they'll inject a contrast dye into you, and X-rays will be taken that show all the blood vessels in the brain. This gives your doctor a map of your blood vessels, pinpointing the aneurysm.

Spinal tap: Your doctor may order this test if they think an aneurysm may have ruptured.

You'll be given a sedative to block any pain, though sometimes this procedure is performed under general aesthesia. Then, a technician will put a needle into you to draw spinal fluid. That fluid is tested to see whether it contains blood, which could mean an aneurysm has ruptured.

Small aneurysms that haven't ruptured and aren't causing symptoms may not need treatment. But this depends on your health and the aneurysm. You can talk this all over with your doctors.

Doctors may consider these factors when deciding to treat an unruptured aneurysm:

  • The size and location of the aneurysm
  • How the aneurysm looks
  • Your age and overall health
  • Your family history
  • Any conditions you were born with that could make a rupture more likely

Brain aneurysm surgery

You need treatment as soon as possible if you have a ruptured brain aneurysm because it's likely that it will bleed again. Treatment involves stopping the blood flow into the aneurysm.

The procedures carry risks. Your doctor will figure out which treatment works best based on your health and the size, type, and location of the aneurysm.

  • Surgical clipping: A section of your skull is removed to locate the aneurysm. A metal clip is placed on the opening of the aneurysm to cut off the blood flow. Your skull is then sealed shut.

  • Endovascular coiling: This doesn't require surgery that opens the skull. Your doctor will insert a catheter into your groin to reach the affected blood vessel where the aneurysm is located. The doctor will send tiny platinum coils through the tube and place them inside the aneurysm. The coils conform to the shape of the aneurysm, stopping the blood flow there. This may be safer than surgical clipping, but it has a higher chance of the aneurysm bleeding again.

  • Flow diverter surgery: This option is for larger brain aneurysms in which neither clipping nor coiling would work. In this procedure, your doctor inserts a stent, usually made of metal mesh, inside the artery. It becomes a wall inside the vessel to divert blood away from the aneurysm.

  • Microvascular clipping: This type of surgery is an open procedure. Surgeons remove a small part of the skull to access the brain. Then, they use imaging tools to find the weakened area of the blood vessel and remove the aneurysm. A titanium clip is placed on the artery to stop bleeding and prevent a future rupture.

Nonsurgical brain aneurysm treatment

To help manage symptoms and prevent complications of an aneurysm, your doctor may suggest:

  • Pain relievers such as acetaminophen
  • Medications called calcium channel blockers that help prevent blood vessels from narrowing
  • Treatments to prevent a stroke, such as drugs that widen the blood vessels so blood will flow through narrowed blood vessels, or a procedure called an angioplasty that uses a small balloon to widen blood vessels
  • Antiseizure medication
  • Ventricular or lumbar draining catheters to reduce pressure on the brain
  • Shunt surgery
  • Rehabilitative therapy to help you relearn skills you may have lost from damage to your brain

A ruptured brain aneurysm can be life-threatening and lead to:

  • Cerebral vasospasm (reduced blood flow to the brain)
  • Hydrocephalus (too much spinal fluid in the brain)
  • Coma
  • Permanent brain damage
  • It bleeding again
  • Hyponatremia (low sodium in your blood)

You may never know that you have an unruptured brain aneurysm. If it doesn't rupture, you may live your entire life without any issues. But there's always a risk that it'll bleed.

If this happens, you'll need immediate medical help. The longer you wait, the worse your outcome could be. Your chances of death or disability go up as more time passes after your aneurysm ruptures.

Around 75% of people with a ruptured brain aneurysm will live longer than 24 hours. But a fourth of these people could have fatal complications within the next 6 months.

If your doctor doesn't treat your aneurysm quickly enough, you might bleed again from the same area. So, it's important to get help as soon as possible if you think you have symptoms of a brain aneurysm.

There are no sure ways to prevent an aneurysm. But here are some steps you can take to lower your risk:

  • Stop smoking if you smoke
  • Keep high blood pressure under control
  • Don't use drugs, such as cocaine
  • Don't drink large amounts of alcohol
  • Eat a balanced diet
  • Work out regularly and avoid constant heavy lifting (stick with moderate exercise)

Most aneurysms aren't serious, but they can be life-threatening if they rupture. Many options are available to treat or prevent a rupture. Your doctor can help you identify the best strategy.

What are the warning signs of a brain aneurysm?

If an aneurysm hasn't ruptured, you may not have any symptoms. Signs of a ruptured aneurysm include:

  • A very bad, sudden headache
  • Stiff neck
  • Nausea and vomiting
  • Blurred or double vision
  • Light sensitivity
  • Seizures
  • Droopy eyelid
  • Confusion
  • A loss of consciousness

Can a human survive a brain aneurysm?

It's possible to survive a brain aneurysm. If the aneurysm ruptures, your chances of survival go down.

What are the chances of surviving a brain aneurysm?

Only about 50% of people with ruptured aneurysms will survive. Of those who make it, about 66% have a permanent brain problem.