Brain aneurysm

Introduction

An aneurysm is a bulge in a blood vessel that's caused by a weakness in the blood vessel wall.

As the blood passes through the weakened blood vessel, the blood pressure causes it to bulge outwards like a balloon.

Aneurysm can occur anywhere in the body but the two most common places for them to form are in the abdominal aorta and the brain (see below).

This topic will be focusing on brain aneurysms. Read our separate topic for information on abdominal aortic aneurysm.

Brain aneurysm

The medical term for an aneurysm that develops inside the brain is an intracranial aneurysm (some doctors also use the term cerebral aneurysm).

Most brain aneurysms will only cause noticeable symptoms if they split open (the medical term for this is a ruptured aneurysm).

This will then trigger an extremely serious condition known as a subarachnoid haemorrhage, where the bleeding caused by the ruptured aneurysm can cause extensive brain damage and symptoms such as:

  • a sudden and severe headache – it has been described as a ‘thunderclap headache’, similar to a sudden hit on the head, resulting in a blinding pain that's unlike anything ever experienced before
  • stiff neck
  • sickness and vomiting

Read more about the symptoms of a brain aneurysm.

A ruptured brain aneurysm is a medical emergency. If you suspect that you or someone in your care has had a ruptured brain aneurysm, call 999 immediately and ask for an ambulance.

Treatment

The goal of treatment is to prevent aneurysms from rupturing in the first place. This is usually done with surgery.

This involves either strengthening the affected blood vessel with tiny metal coils or sealing it shut with a tiny metal clip. But not all aneurysms are routinely treated in this way.

Surgery carries a small risk of causing serious complications, some of which can be fatal. Therefore surgery is usually recommended only if the potential risk of the aneurysm rupturing outweighs the risks associated with surgery

The size and location of the aneurysm is often used to measure the risk of it rupturing. An aneurysm larger than 7mm or located in a section of blood vessel known as the posterior communicating artery has an increased risk of rupture.

A number of non-surgical treatments can also be used to reduce the risk of an aneurysm rupturing. They include a type of medication known as a statin, or quitting smoking if you smoke.

Read more about the treatment of aneurysms.

Causes

Exactly what causes the wall of affected blood vessels to weaken is still unclear though a number of risk factors have been identified.

These include:

In some cases, an aneurysm may develop because there was a weakness in the walls of the blood vessels at birth.

Aneurysms are also known to run in families.

Read more about the possible risk factors and causes of aneurysms.

Who is affected

It's difficult to estimate exactly how many people are affected by a brain aneurysm because in most cases they cause no symptoms and pass undetected. Some experts believe it could be as high as 1 in 20 people while others think the figure is much lower at around 1 in a 100 people.

Thankfully, the number of aneurysms that actually rupture is much smaller.

Prevention

The best way to prevent getting an aneurysm, or reduce the risk of an aneurysm growing bigger and possibly rupturing, is to avoid any activities that could damage your blood vessels, such as:

  • smoking
  • eating a high-fat diet
  • not exercising regularly
  • being overweight or obese

Read more about preventing aneurysms.

 

Glossary

Aneurysm
An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Artery
Arteries are blood vessels that carry blood from the heart to the rest of the body.

Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Blood vessel
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are
veins, arteries and capillaries.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Congenital
Congenital means a condition that is present at birth- the condition could be hereditary or develop during pregnancy.

Heart
The heart is a muscular organ that pumps blood around the body.

High blood pressure
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.

Swelling
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Last updated: 23 February 2012

Symptoms of a brain aneurysm

In most cases, an unruptured brain aneurysm will cause no symptoms unless it becomes big or begins to press against tissues or nerves inside the brain.

Symptoms of an unruptured brain aneurysm may include:

  • visual disturbances, such as loss of vision or double vision
  • difficulties moving one of your eyes
  • pain on one side of your face or around your eye
  • inability to move some of your facial muscles; usually only one side of your face is affected
  • headaches
  • seizures (fits)

If you do experience symptoms of a brain aneurysm, it's normally recommended that the aneurysm is treated as soon as possible.

Ruptured brain aneurysm

Symptoms of a ruptured brain aneurysm usually begin with a sudden and severe headache. It's been likened to being hit on the head, resulting in a blinding pain that's unlike anything ever experienced before.

Other symptoms include:

  • stiff neck
  • feeling sick
  • being sick
  • slurred speech
  • sensitivity to light
  • blurred or double vision
  • mental confusion
  • loss of consciousness

Medical emergency

A ruptured brain aneurysm is a medical emergency. If you suspect that you or someone in your care has had a ruptured brain aneurysm, call 999 immediately and ask for an ambulance.

 

Glossary

Aneurysm
An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Haematoma
Haematoma is a collection of blood in the tissues from a leaking blood vessel, which causes bruising.

Nausea
Nausea is when you feel like you are going to be sick.

Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.

Ruptures
A rupture is a break or tear in an organ or tissue.

Spine
The spine supports the skeleton, and surrounds and protects the delicate spinal cord and nerves. It is made up of 33 bones called the vertebrae.

Tissue
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.  

Vomiting
Vomiting is when you bring up the contents of your stomach through your mouth.

Last updated: 03 June 2012

Causes of a brain aneurysm

The brain requires a large supply of blood due to its size and complexity (the brain uses a quarter of all the blood in the human body).

The supply of blood is delivered to the brain by four main blood vessels, which run up the neck and into the brain. These blood vessels divide into smaller and smaller vessels in the same way that a trunk of a tree divides into branches and twigs.

Most aneurysms develop at the points where the blood vessels divide and branch off because these are the sections where the vessel walls are weakest.

Risk factors for a brain aneurysm

In some cases, brain aneurysms are caused by pre-existing (present from birth) weaknesses in the blood vessels.

There are also a number of risk factors that can cause you to develop a brain aneurysm. These are discussed below.

Smoking

Smoking cigarettes is a major risk factor for developing a brain aneurysm. A study published in 2010 found that 8 out of 10 people who were diagnosed with a brain aneurysm were smokers or had smoked in the past.

The risk is particualry high in people with a family history of brain aneurysm (see below).

Exactly why this is the case in unclear. There may be harmful substances in tobacco smoke that could damage the walls of blood vessels.

High blood pressure

High blood pressure can place increased pressure on the walls of the blood vessels inside the brain.

You are more likely to develop high blood pressure if you:

  • are overweight
  • have a relative with high blood pressure
  • are of African or Caribbean descent
  • eat a lot of salt
  • don't eat many fruit and vegetables
  • don't do enough exercise
  • drink a lot of coffee (or other caffeine-based drinks)
  • drink a lot of alcohol
  • are aged over 65

Read more about high blood pressure.

Family history

Family history can be a risk factor. Having a first-degree relative with a history of a brain aneurysm means that you're twice as likely to develop one than someone with no family history of the condition.

However, the increased risk is still small – only around 1 in 50 people with a family history of a ruptured brain aneurysm will go on to have a rupture themselves.

Cocaine

Cocaine abuse is another risk factor for brain aneurysms. Cocaine can inflame the walls of the blood vessels and raise your blood pressure. The combination of these two factors increases your risk of developing a brain aneurysm.

Autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic condition that causes multiple cysts to develop on the kidneys. Cysts are small sacs that are filled with fluid.

Around 1 in every 1,000 people is born with ADPKD. Of these people, around 1 in 20 will develop an aneurysm in the brain.

Read more about autosomal dominant polycystic kidney disease.

 

Glossary

Aneurysm
An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Artery
Arteries are blood vessels that carry blood from the heart to the rest of the body.

Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Blood vessel
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Cholesterol
Cholesterol is a fatty substance made by the body that is found in blood and tissue. It is used to make bile acid, hormones and vitamin D.

Genetic
Genetic is a term that refers to genes, the characteristics inherited from a family member.

High blood pressure
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.

Obesity
Obesity is when a person has an abnormally high amount of body fat.

Platelets
Platelets are cells in the blood that control bleeding by plugging the broken blood vessel and helping the blood to clot.

Rupture
A rupture is a break or tear in an organ or tissue.

Last updated: 03 June 2012

Diagnosing a brain aneurysm

A brain aneurysm can be detected using a special kind of X-ray called an angiogram or arteriogram. To highlight the aneurysm, a dye is injected into the bloodstream. The blood in the vessels shows up on the film as white columns.

If a blood vessel is swollen due to an aneurysm, the dye in the blood will pass into it and the X-ray will show the swelling.

If surgery is being planned you may be referred for further testing so that the surgeon can obtain more information on the precise location of the aneurysm.

These tests may include:

Screening

There's no routine screening programme for a brain aneurysms and it's unlikely that one will be introduced in the future.

This is because researchers have calculated that routine screening would do little in preventing deaths but would place a significant drain on NHS resources.

Screening is only recommended for people who are thought to have a significant risk of having a brain aneurysm that could rupture at some point in the future.

This would usually only apply to you if you had two or more first-degree relatives (father, mother, sister or brother) who had experienced a subarachnoid haemorrhage (bleeding inside the brain due to a ruptured aneurysm).

If this applies to you then you should contact your GP. They will be able to refer you to a specialist clinic for further assessment.

Be aware that discovering you have an aneurysm that's unsuitable for surgical treatment can cause worry and distress, even though the risk of it rupturing is small. Some people have reported that they regretted getting screened. There are no right or wrong answers but it's important that you discuss the potential implications of screening with the staff of the clinic.

Screening may also be recommended if you have the genetic condition autosomal dominant polycystic kidney disease.

 

Glossary

Aneurysm
An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Arteries
Arteries are blood vessels that carry blood from the heart to the rest of the body.

Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Kidneys
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.

Swelling
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Ultrasound scan

Ultrasound scans are a way of producing pictures of inside the body using sound waves.

X-ray
An X-ray is a painless way of producing pictures of inside the body using radiation.

Last updated: 03 June 2012

Treating a brain aneurysm

There are two main types of treatment for a brain aneurysm:

  • preventative treatment: where an aneurysm is treated to prevent it from rupturing
  • emergency treatment: where an aneurysm is repaired after it ruptures

The mainstay of preventative treatment is surgery, though as with any type of surgery, it carries a risk of complications, some of which are serious, such as brain damage or a stroke.

Therefore, preventative surgery is usually only recommended if it's thought that the risk of a rupture is significant enough to justify the risk of surgery.

Preventative treatment

If you are diagnosed with a brain aneurysm, a risk assessment will be carried out to assess the risk of the aneurysm rupturing.

The assessment process is usually based on the following factors:

  • your age
  • the size of the aneurysm
  • where in the brain the aneurysm is located; brain aneurysms that are located near larger blood vessels have a high risk of a rupture
  • whether you have a family history of ruptured brain aneurysm
  • whether you have an underlying health condition that increases the risk of a rupture, such as autosomal dominant polycystic kidney disease or poorly controlled high blood pressure

The decision to surgically repair an aneurysm will be based on a number of factors individual to you, such as:

  • your age – research has found that in older adults the potential benefit of surgery in terms of extending natural lifespan is often outweighed by the risks associated with surgery
  • the size of the aneurysm – aneurysms larger than 7mm often require surgical treatment as do aneurysms larger than 3mm in cases where there are other risk factors
  • the location of the aneurysm – as mentioned above, aneurysms located near larger blood vessels have a high risk of a rupture

Your surgical team should be able give you a detailed assessment of whether the benefits of surgery outweigh the potential risks in your individual case.

Active observation

If it is thought that the risk of rupture is small then a policy of active observation is normally recommended.

Active observation means that you won't receive immediate surgery, but you'll be given regular check-ups so that your aneurysm can be carefully monitored.

You'll be referred for regular angiograms so that the size of the aneurysm can be carefully monitored.

You may also be given medication to lower your blood pressure as well as discussing lifestyle changes, such as losing weight and reducing the amount of fat in your diet.

Surgery

Two surgical techniques have proved to successfully treat brain aneurysms: neurosurgical clipping and endovascular coiling.

Neurosurgical clipping

Neurosurgical clipping is a procedure carried out under general anaesthetic (you're asleep throughout). A cut is made in your scalp and a small flap of bone is removed to reveal your brain underneath.

When the aneurysm is located, the neurosurgeon (an expert in surgery of the brain and nervous system) will seal it shut using a tiny metal clip. After the bone flap has been replaced, the scalp is stitched together.

Endovascular coiling

Endovascular coiling involves inserting a catheter into an artery in your leg or groin. The tube is guided through the network of blood vessels into your head and finally into the aneurysm.

Tiny platinum coils are then passed through the tube into the aneurysm. The coils block the flow of blood into the aneurysm. Over time this should seal the aneurysm off from the main artery to prevent it from rupturing.

Coiling or clipping?

Coiling is thought to be slightly more effective in preventing death in the long term than clipping.

One study found that 1 in 10 people treated with coiling died in the first five years after surgery compared to 1 in 7 people treated with clipping.

Both techniques have similar levels of effectiveness in reducing the risk of a person becoming disabled as a result of bleeding inside the brain.

An advantage of coiling is that it's less invasive so it has a faster recovery time. Also, due to the less invasive nature of treatment, there's a reduced risk of a person having seizures (fits) after surgery, which is a common complication of invasive brain surgery.

Though there may be circumstances when coiling is not technically possible or suitable – e.g. the aneurysm is located in a part of the brain that can't be reached using a catheter.

Your surgical team will be able to provide more information about the pros and cons of both techniques.

Emergency treatment

Emergency treatment is based on the same principles as preventative treatment. Coils or clipping are used to repair ruptured brain aneurysms.

Due to the urgent nature of a ruptured aneurysm, the decision to perform open or endovascular surgery may be determined by the expertise and experience of the surgeons available.

Additional medication and treatments may also be used to prevent blood loss and organ damage. For example, nimodipine may be recommended. This medication is used to prevent ruptured blood vessels going into spasm and causing further blood loss.

 

Glossary

Aneurysm
An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Artery
Arteries are blood vessels that carry blood from the heart to the rest of the body.

Blood

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Brain

The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Drip

A drip is used to pass fluid or blood into your bloodstream, through a plastic tube and needle that goes into one of your arteries or veins.

Haemorrhage
To haemorrhage means to bleed or lose blood. 

Ruptures
A rupture is a break or tear in an organ or tissue.

Tissue
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.  

Last updated: 03 June 2012

Preventing a brain aneurysm

While not all the risk factors for aneurysms can be prevented, the two leading risk factors can.

These are:

  • smoking
  • high blood pressure

Smoking

Smoking is a major risk factor for aneurysms because it causes atherosclerosis and raises your blood pressure. There may also be harmful substances in tobacco smoke that could damage the walls of the arteries.

If you decide to stop smoking, your GP will be able to refer you to an NHS Stop Smoking Service, which will give you dedicated help and advice about the best ways to give up smoking. You can also call Smokleline on 0800 84 84 84. The specially trained helpline staff can offer you free expert advice and encouragement.

If you're committed to giving up smoking but don't want to be referred to a stop-smoking service, your GP should be able to prescribe medical treatment to help with any withdrawal symptoms that you may have after quitting.

See Treatment for quitting smoking and CanStopSmoking for more information about giving up.

High blood pressure

High blood pressure can often be reduced by eating a healthy diet, moderating your alcohol intake, maintaining a healthy weight and doing regular exercise.

Diet

Cut down on the amount of salt in your food and eat plenty of fruit and vegetables.

Salt raises your blood pressure. The more salt you eat, the higher your blood pressure. Aim to eat less than less than 6g (0.2oz) of salt a day – about a teaspoonful.

Eating a low-fat diet that includes lots of fibre (for example, wholegrain rice, bread and pasta) and plenty of fruit and vegetables has been proven to help lower blood pressure. Fruit and vegetables are full of vitamins, minerals and fibre to keep your body in good condition. You should aim to eat five 80g portions of fruit and vegetables every day.

Alcohol

Regularly drinking alcohol above what the NHS recommends will raise your blood pressure over time. Staying within the recommended levels is the best way to reduce your risk of developing high blood pressure.

The NHS recommends:

  • men shouldn't regularly drink more than 3-4 units a day
  • women shouldn't regularly drink more than 2-3 units a day

Alcohol is also high in calories, which will make you gain weight. This will also increase your blood pressure.

Further information can be found in the Alcohol Zone

Weight

Being overweight forces your heart to work harder to pump blood around your body, which can raise your blood pressure.

If you need to shed some weight, it's worth remembering that losing just a few pounds will make a big difference to your blood pressure and overall health.

Exercise

Being active and taking regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition. Regular exercise can also help you lose weight, which will also help lower your blood pressure.

Adults should do at least 150 minutes (two hours and 30 minutes) of moderate-intensity aerobic activity (i.e. cycling or fast walking) every week. For it to count, the activity should make you feel warm and slightly out of breath. Someone who is overweight may only have to walk up a slope to get this feeling.

Physical activity can include anything from sport to walking and gardening.

Read more about preventing high blood pressure.

 

Glossary

Aneurysm
An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.

Artery
Arteries are blood vessels that carry blood from the heart to the rest of the body.

Blood
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Cholesterol
Cholesterol is a fatty substance made by the body that lives in blood and tissue. It is used to make bile acid, hormones and vitamin D.

High blood pressure
Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.

Platelets
Platelets are cells in the blood that control bleeding by plugging the broken blood vessel and helping the blood to clot.

Rupturing
A rupture is a break or tear in an organ or tissue.

Ultrasound

Ultrasound scans are a way of producing pictures of inside the body using sound waves.

Last updated: 03 June 2012