Intracranial Aneurysm

An intracranial aneurysm is a dangerous bulge in a blood vessel in your brain that can burst without warning, causing life-threatening bleeding. While most brain aneurysms are small and may never cause problems, a ruptured aneurysm is a medical emergency that can lead to stroke, brain damage, or death.

Table of contents

• What is an intracranial aneurysm?
• Types of brain aneurysms
• Warning signs and symptoms
• Risk factors
• What happens when an aneurysm ruptures?
• How doctors find brain aneurysms
• Treatment options
• How common are brain aneurysms?
• Living with a brain aneurysm

What is an intracranial aneurysm?

An intracranial aneurysm, also called a cerebral aneurysm or brain aneurysm, is a bulge or ballooning in a blood vessel in the brain. This happens when a weak spot develops in the wall of a blood vessel^[1]. The constant pressure of blood flowing through the vessel pushes the weakened section outward, creating a blister-like bump^[3].

Think of it like a thin balloon or a weak spot on a tire’s inner tube. As blood rushes into this bulge, the aneurysm stretches even farther, similar to how a balloon gets thinner and more likely to pop as it fills with air^[3][7].

Brain aneurysms can occur anywhere in the brain, but most form in the major arteries along the base of the skull^[1]. Approximately 10% to 30% of people who have a brain aneurysm have multiple aneurysms^[3].

The majority of brain aneurysms are small and don’t cause symptoms. Most people find out they have a brain aneurysm when they get imaging for another reason and it shows up on the scan^[3][6]. However, if an aneurysm leaks or ruptures (bursts open), it causes bleeding in the brain and becomes a life-threatening emergency^[1].

cerebral aneurysm, brain aneurysm

Types of brain aneurysms

Brain aneurysms are classified by both their size and shape. Understanding these differences helps doctors decide on the best treatment approach^[4].

By size, aneurysms are grouped as:

• Small aneurysms: less than 15 millimeters in diameter
• Large aneurysms: 15 to 25 millimeters
• Giant aneurysms: 25 to 50 millimeters
• Super-giant aneurysms: over 50 millimeters^[4]

The most common type by shape is a saccular aneurysm, also known as a berry aneurysm because it looks like a berry hanging on a stem. These aneurysms bulge on only one side of the artery wall and have a “neck” that connects the aneurysm to its main artery and a larger, rounded area called the dome^[1][4][7].

A less common type is a fusiform aneurysm, in which the artery is widened on both sides. Fusiform aneurysms do not have a defined neck^[7].

Microaneurysms are very small aneurysms that can occur in tiny blood vessels^[4].

Warning signs and symptoms

Brain aneurysm symptoms vary greatly depending on whether the aneurysm has ruptured or remains intact. Most small, unruptured brain aneurysms don’t cause any symptoms at all^[2][6].

Symptoms of an unruptured aneurysm

Large, growing aneurysms may press on brain tissue and nerves, causing symptoms such as^[2][3]:

• Pain above and behind the eye
• Numbness
• Weakness
• Paralysis (inability to move muscles) on one side of the face
• Increase in the size of the eye pupil
• Vision changes or double vision
• Headaches
• Dizziness and balance problems
• Difficulty concentrating and speaking
• Problems with short-term memory^[6]

Symptoms of a ruptured aneurysm

When an aneurysm ruptures, it causes a sudden, severe headache. Some people describe it as the worst headache of their life, sometimes called a thunderclap headache^[2][3][6].

Other symptoms of a ruptured aneurysm include^[2][3]:

• Nausea and vomiting
• Stiff neck
• Blurred or double vision
• Sensitivity to light
• Seizures
• Drooping eyelid and a dilated pupil
• Weakness or numbness in one arm or down one side of the body
• Speech problems, such as slurring words or sounding confused
• A brief or prolonged loss of consciousness
• Cardiac arrest (the heart stops beating)^[2]

If you or someone else suddenly gets these symptoms, call emergency services immediately. A ruptured brain aneurysm is a medical emergency that requires immediate treatment^[6].

Risk factors

Several factors can increase your chances of developing a brain aneurysm. Some of these factors are within your control, while others are not^[4][6].

Risk factors include:

• High blood pressure (hypertension)
• Smoking
• Heavy alcohol consumption
• Cocaine and amphetamine use
• Intravenous drug abuse
• Heavy caffeine intake
• Head trauma or injury to a blood vessel in the brain
• Blood infections
• Having a close relative who has had a brain aneurysm
• Certain genetic conditions, such as autosomal dominant polycystic kidney disease or Ehlers-Danlos syndrome^[4][6]

Brain aneurysms can affect anyone at any age, but they’re most likely to affect people between the ages of 30 and 60. They’re also more common in women^[3].

What happens when an aneurysm ruptures?

When a brain aneurysm ruptures, blood spills into the surrounding brain tissue or the space between the brain and skull. This bleeding is called a hemorrhage^[3].

Most often, a ruptured brain aneurysm causes bleeding in the space between the brain and the thin tissues covering the brain. This type of bleeding is called a subarachnoid hemorrhage. About 90% of subarachnoid hemorrhages are due to ruptured brain aneurysms^[1][3].

The blood can put excess pressure on brain tissue and make the brain swell. This can result in serious health problems such as^[2][3]:

• Hemorrhagic stroke: bleeding in the space between the skull and brain
• Vasospasm: blood vessels get narrower or clamp down and less oxygen reaches the brain
• Hydrocephalus: a buildup of cerebrospinal fluid or blood around the brain that puts increased pressure on it
• Delayed cerebral ischemia: one of the biggest causes of complications and death after a ruptured aneurysm, occurring between 3 and 14 days after bleeding^[2]
• Seizures: a temporary, uncontrolled surge of electrical activity in the brain
• Coma: a state of prolonged unconsciousness that can last days to weeks
• Permanent brain damage
• Death^[3]

Ruptured brain aneurysms result in death in about 50% of cases. As more time passes with a ruptured aneurysm, the likelihood of death or disability increases^[3].

How doctors find brain aneurysms

Doctors use several tests to detect and diagnose brain aneurysms. The specific tests depend on whether the aneurysm has ruptured and what symptoms are present^[8].

Common diagnostic tests include:

CT scan (Computed Tomography): This specialized X-ray is usually the first test used to assess for bleeding in the brain. A CT angiogram can create detailed images of the arteries providing blood flow in the brain and can detect the presence of an aneurysm^[8].

Lumbar puncture (spinal tap): If you’ve had a subarachnoid hemorrhage, there will most likely be red blood cells in the fluid surrounding your brain and spine, called cerebrospinal fluid. If symptoms suggest a ruptured aneurysm but a CT scan doesn’t show evidence of bleeding, this test can help make a diagnosis^[8].

MRI (Magnetic Resonance Imaging): This imaging test uses a magnetic field and radio waves to create detailed images of the brain. These images can show if there’s bleeding in the brain. A type of MRI called MR angiography can detect the size, shape, and location of an aneurysm^[8].

Cerebral angiogram: During this procedure, a thin, flexible tube called a catheter is inserted into an artery, usually in the groin or the wrist. The catheter threads past your heart to the arteries in your brain. A special dye injected into the catheter travels to arteries throughout your brain, and a series of X-rays can reveal details about the conditions of your arteries and detect an aneurysm^[8].

Treatment options

Treatment for a brain aneurysm depends on several factors, including whether it has ruptured, its size and location, your age and health, and the risks of treatment^[1][8].

For unruptured aneurysms

Not all unruptured aneurysms need immediate treatment. Those that are very small (less than 3 millimeters) are less likely to break open. Your doctor will help you decide whether it’s safer to have treatment to block off the aneurysm before it can rupture, or to monitor it over time^[11][15].

Watchful waiting: If the risks of surgery outweigh the risk of rupture, doctors may recommend monitoring the aneurysm with regular imaging tests to see if it gets bigger. Lifestyle changes such as quitting smoking and controlling blood pressure can significantly reduce the risk of aneurysm growth and rupture^[11][15].

Medication: Doctors may prescribe medication to manage risk factors such as high blood pressure, to further reduce the risk of an aneurysm rupturing^[11].

Treatment procedures

Two main methods are used to repair a brain aneurysm^[8]:

Surgical clipping: This is done during open brain surgery (craniotomy). An incision is made in the skin of the head and a small piece of bone, called a bone flap, is removed to access the aneurysm directly. A small metal clip is then fastened to the neck of the aneurysm, stopping blood flow into it. The bone flap is then reattached, and the incision closed^[11].

Endovascular coiling: This is the most common treatment for brain aneurysms and is less invasive than surgical clipping. It does not require opening of the skull. Surgeons access the aneurysm through a catheter inserted into arteries in the arm or groin. Treatment consists of inserting small metal coils into the aneurysm, or using a newer technology called flow diversion. Flow diversion involves inserting a stent into the artery along the aneurysm, which significantly reduces and later blocks blood flow into the aneurysm^[5][11].

Approximately 300 aneurysms each year are treated with endovascular coiling at some major medical centers, placing this procedure at the forefront of innovative treatment with demonstrated effectiveness, particularly for patients with ruptured aneurysms^[5].

For ruptured aneurysms

A ruptured aneurysm requires immediate medical treatment. Treatment decisions should be based on the clinical status of the patient, the anatomy of the aneurysm, and surgical or endovascular considerations^[13].

Medical management in the intensive care unit includes controlling blood pressure, administering calcium channel blockers, and preventing seizures. After the aneurysm is treated, blood pressure is maintained at higher levels to reduce complications associated with vasospasm, which usually occurs between days 3 and 21 after rupture^[13].

How common are brain aneurysms?

Up to 6% of people in the United States have an aneurysm in their brain that isn’t bleeding (an unruptured aneurysm). This means that brain aneurysms are relatively common. One in fifty people has a brain aneurysm, but only a small number of these aneurysms cause symptoms or rupture^[3][7].

Ruptured brain aneurysms are less common. They occur in approximately 30,000 people in the U.S. per year. Every year, approximately 30,000 patients in the U.S. suffer from a ruptured cerebral aneurysm^[3][9].

Without access to treatment, the fatality rate is 50% in the first 30 days after rupture^[10].

Living with a brain aneurysm

Finding out you have a brain aneurysm can be scary and worrying. Understanding what it means and how to protect your health is important^[15].

Lifestyle changes

If you have a brain aneurysm, there are some things you can do to reduce the risk of it getting bigger and bursting^[6]:

• Stop smoking if you smoke
• Keep your blood pressure at a healthy level
• Make healthy lifestyle changes, such as eating a balanced diet, exercising regularly, and losing weight if you’re overweight
• Don’t drink too much alcohol
• Don’t take illegal drugs^[6]

Long-term effects and recovery

For people who survive a brain aneurysm, damage from pressure and bleeding may pose long-term health effects. The potential long-term effects of a brain aneurysm may be mental and physical, and they depend on what parts of the brain are affected^[21].

Common long-term effects after a brain aneurysm include^[9][21]:

• Depression and anxiety
• Chronic headaches
• Physical and mental fatigue
• Memory loss and impaired short-term memory
• Physical impairment, including weakness in the extremities
• Loss of coordination and affected balance
• Speech difficulties
• Perception changes
• Inability to concentrate
• Limited emotional regulation
• Mood disorders
• Personality and behavioral changes

Survivors can often feel a loss of control over their emotions, meaning they may be prone to acting out in anger or frustration at a moment’s notice. Changes in self-esteem and self-confidence due to new physical and mental limitations are also common^[14].

Depression and anxiety after treating a brain aneurysm could happen to 1 in 5 patients. Unfortunately, it’s often under-diagnosed, and survivors don’t know they should be seeking treatment for depression because they are dealing with so many other adjustments at the same time^[14].

Support and resources

Finding a group that understands your emotions and the road through recovery is essential when needing an outlet and support. Survivors of brain aneurysms and other brain injuries can still lead a completely normal and healthy life, though they often need to adjust in large and dramatic ways to their new way of living^[14].

As well as getting help and advice from your doctor, you may find it helpful to talk to other people with the condition, either at a local support group or online. Organizations such as the Brain Aneurysm Foundation, Headway, and the Brain and Spine Foundation provide information, help, and support for anyone affected by brain aneurysm^[6][14].