An aneurysm is a bulge in a blood vessel that is caused by a weakness in the blood vessel wall. As the blood passes through the weakened part of the vessel, the blood pressure causes it to bulge outwards like a balloon.

If the aneurysm grows too big, there is a danger that it will rupture (split) which can cause potentially fatal internal bleeding and organ damage.

Types of aneurysms

An aneurysm can develop anywhere in the body but the two most common types of aneurysms are:

• an intracranial aneurysm (also known as a cerebral aneurysm), which develops inside the brain, and
• an aortic aneurysm, which develops inside the aorta. The aorta is a large blood vessel that runs down the abdomen and transports blood away from the heart.

Ruptured aneurysms

A rupture in an intracranial aneurysm or an aortic aneurysm can have a potentially devastating effect on the body.

A ruptured intracranial aneurysm can lead to blood leaking out over the surface of the brain. This is known as a subarachnoid haemorrhage. The blood can cause brain damage and lead to a reduction in blood supply that, in turn, can cause further brain damage. Without emergency treatment, a subarachnoid haemorrhage will usually result in death.

A ruptured aortic aneurysm can cause massive internal bleeding. Without emergency treatment, a ruptured aortic aneurysm will result in death.

The risk of an aneurysm rupturing is small. It is estimated that there is a 0.05% to 0.5% risk that an intracranial aneurysm will rupture in any given year.

There is not enough evidence to estimate a similar risk figure for aortic aneurysms, although known risk factors for rupture include:

• if the aneurysm is larger than 5.5cm (2.15 inches), and 
• if there is a family history of ruptured aneurysm.

How common are aneurysms?

Aortic aneurysms usually develop in people who are 65 years of age or over, and they are thought to be more common in men than women. It is estimated that between 1.3 and 8.9% of older men, and 1 and 2.2% of older women have an aortic aneurysm.

As unruptured aneurysms do not usually cause symptoms, it is difficult for researchers to give more accurate estimates.

Ruptured aneurysms are a small but significant cause of death in the UK. In the UK each year, an estimated 8,000 people die because of a ruptured aortic aneurysm and an estimated 1,400 people die as a result of a ruptured intracranial aneurysm.

In many cases, the exact cause of an aneurysm is often unclear, but known risk factors include:

• smoking,
• high blood pressure (hypertension), and
• having a family history of aneurysms.

Preventative treatment and screening

Due to the potentially fatal risks associated with a ruptured aneurysm, preventative treatment is recommended if the risk of a rupture is considered to be above average.

Treatment usually involves clipping the aneurysm closed using a tiny metal clip, plugging the flow of blood with coils of metal wires, or removing a section of the blood vessel and replacing it with a piece of tubing, known as a graft.

In March 2009, the NHS in England launched a pilot screening service designed to check men who are 65 years of age or over for aortic aneurysms. Wales, Scotland and Northern Ireland all plan to implement their AAA screening programmes in 2012.  England is on course to have full implementation by 2013.

Outlook

In cases of ruptured aneurysms, the outlook is poor.

An estimated 65-85% of people with a ruptured aortic aneurysm will die, and about half of all deaths occur before the person is taken to hospital.

An estimated 10% of people with a ruptured intracranial aneurysm will die before reaching hospital and a further 50% of people will die within one month.

Half of all people who survive an intracranial aneurysm will experience brain damage.

Unruptured aneurysms

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

Unruptured aortic aneurysm

Symptoms of an unruptured aortic aneurysm include:

• a vibrating sensation in your abdomen, usually near your navel (belly button), that is usually only noticeable when you touch it,
• chronic (long-lasting) back pain, and
• chronic abdominal pain.

Unruptured intracranial aneurysm

Symptoms of an unruptured intracranial aneurysm 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,
• paralysis of some of your facial muscles,
• headaches, and
• seizures (fits).

Ruptured aortic aneurysm

If your aortic aneurysm ruptures, you will experience a sudden and severe pain in the middle or side of your abdomen. In men, the pain can also radiate down into the scrotum.

Other symptoms include:

• dizziness,
• sweaty and clammy skin,
• rapid heartbeat (tachycardia),
• shortness of breath,
• feeling faint, and
• loss of consciousness.

Ruptured intracranial aneurysm

Symptoms of a ruptured intracranial aneurysm usually begin with a sudden and severe headache, which has been described as like being hit on the head, resulting in a blinding pain that is unlike anything ever experienced before.

Other symptoms include:

• stiff neck,
• sickness and vomiting,
• slurred speech,
• sensitivity to light (photophobia),
• blurred or double vision,
• mental confusion, and
• loss of consciousness.

Aortic aneurysms

The aorta is the largest blood vessel in the body, and is responsible for moving oxygen-rich blood away from your heart and lungs to the rest of the body.

The aorta is a hollow tube, about the width of a hosepipe. The wall of the aorta is made up of elastic fibres that are a mixture of proteins and collagen (a tough, flexible type of protein).

In cases of aortic aneurysm, the normal mixture of elastic fibres and collagen becomes disrupted, leading to a weakening in part of the aortic wall. The large amount of blood that passes through the aorta will place pressure on the weak spot in the wall, causing it to bulge outwards to form an aneurysm.

Risk factors for an aortic aneurysm

It is not known exactly what causes the aortic wall to weaken. However, a number of factors, many of which are interlinked, have been related to an increased risk of developing an abdominal aortic aneurysm. These are explained below.

• Atherosclerosis: this is a condition where blood vessels, such as the aorta, become harder and narrower. It can be caused by high-cholesterol, smoking and high blood pressure (hypertension).
• Smoking: people who smoke tobacco are four times more likely to develop an aortic aneurysm compared to non-smokers. This may be due to smoking's link with atherosclerosis, but there may also be substances in tobacco smoke that directly weaken the aortic wall.
• High blood pressure: if the blood is pumped through the aorta at a higher pressure than normal, it may weaken the aortic wall.
• Family history: research has found that someone with a first-degree relative, such as a parent, brother, or sister, who has an aortic aneurysm, will have a 20% chance of developing the condition themselves, compared to a 1 to 3% risk in a person with no family history of aneurysm.

Intracranial aneurysm

The brain requires a large supply of blood due to its size and complexity (the brain uses 25% of all the blood in the human body).

The supply of blood is delivered to the brain by two main blood vessels that 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 an intracranial aneurysm

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

Anything that alters the normal flow of blood through the brain can also be a risk factor for an intracranial aneurysm. Common risk factors include:

• atherosclerosis (narrowing of the arteries),
• smoking,
• high blood pressure (hypertension), and
• severe head injury.

Family history can be a risk factor. Having a first-degree relative with a history of intracranial aneurysm means that it is twice as likely that you will develop an intracranial aneurysm compared to someone with no family history of the condition. However, the increased risk is still small, estimated at 4.2%.

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

There are also a number of health conditions that can increase your risk of developing an intracranial aneurysm. These include:

• polycystic kidney disease: a genetic disorder that affects the kidneys and causes chronic high blood pressure, and
• Marfan syndrome: a genetic disorder where the fibres that make up the blood vessels are not properly formed.

Aortic aneurysm

Abdominal aortic aneurysms are often diagnosed during a routine physical examination when a GP notices the distinctive vibrating sensation in the abdomen.

A diagnosis can be confirmed using an ultrasound scan. Ultrasounds can also determine the size of the aneurysm, which is an important factor in deciding on a course of treatment.

Intracranial aneurysm

A brain aneurysm can be detected using a special kind of X-ray that is 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.

Computer topography (CT) scans and magnetic resonance imaging (MRI) scans can also be used to produce detailed images of the structure of blood vessels inside the brain.

Screening

In March 2009, the NHS in England launched a pilot screening service in certain areas, designed to check men who are 65 years of age or over for aortic aneurysms. Wales, Scotland and Northern Ireland all plan to implement their AAA screening programmes in 2012.  England is on course to have full implementation by 2013.

If you do not live in a part of the country that is currently covered by the screening programme, you can still request an ultrasound scan for aortic aneurysm. Contact your GP for more information.

There is currently no screening programme for intracranial aneurysms.

It is recommended that you undergo screening for intracranial aneurysms every five years if you have two or more close (first-degree) blood relatives, such as your mother, father, brother, aunt or uncle (but not your grandmother or grandfather) who have experienced a subarachnoid haemorrhage. Your GP can refer you to a neurologist for further assessment.

There are two main types of treatment for aneurysm:

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

Preventative treatment is the preferred option but, as with any type of surgery, it does carry a risk of complications, some of which are serious, such as brain damage or organ failure.

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

Preventative treatment for aortic aneurysm

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

The assessment is usually based on five factors:

• Your age.
• The size of the aneurysm.
• How quickly the aneurysm is growing.
• Whether you have a first-degree relative (defined as parents, siblings, aunts or uncles) who has experienced a ruptured aneurysm.
• Whether you have high levels of a chemical called MMP-9 in your blood. High levels of MMP-9 can be caused by extensive weakening of the aortic wall.

Usually, the recommended treatment options are:

• A policy of watchful waiting, if the size of the aneurysm is less than 5cm (see below for more details).
• Preventative surgery, if the size of the aneurysm is from 5 to 5.5cm (2 to 2.2 inches), and you have one of the risk factors mentioned above,.
• Surgery, if the aneurysm is larger than 5.5cm regardless of whether or not you have any associated risk factors.

Watchful waiting

Watchful waiting means that you will not receive immediate surgery, but you will be given regular check-ups so that your aneurysm can be carefully monitored. This usually involves having an ultrasound every three or six months.

You may be given medication to treat any underlying conditions.

Lifestyle changes that will help decrease your risk of a rupture may also be recommended. These may include:

• eating a healthy, balanced diet and reducing the amount of fat in your diet,
• stopping smoking (if you are a smoker), and
• losing weight (if you are overweight).

Surgery

The most commonly used surgical treatment for aortic aneurysms is grafting. This involves removing the affected section of the aorta, and replacing it with a piece of synthetic tubing known as a graft.

There are two ways that grafting can be done:

• Open surgery. A large incision (cut) is made in your abdomen to expose the aorta and insert the graft.
• Endovascular surgery. This involves sticking a thin tube, called a catheter, into one of the veins in your legs and then guiding it to the aorta. The graft is then moved through the catheter and used to reinforce the aorta wall.

For more information, see Repair of aortic aneurysm.

Open or endovascular surgery?

Each surgical technique has its own set of advantages and disadvantages. As endovascular surgery is non-invasive (does not involve making major incisions into the body) it has a quicker recovery time. Research also suggests that it offers a slightly better chance of reducing the risk of death from an aneurysm (by about 3%).

However, the same research found that rates of complications after the endovascular surgery, such as the graft splitting or becoming infected, were much higher than in open surgery. Approximately 41% of people who received endovascular surgery experience complications compared with only 9% of people who received open surgery.

The main disadvantage in open surgery is that it requires making a major incision in your abdomen. Therefore it could take you several months to recover from the operation. Open surgery may also not be suitable for people who are unwell due to other health conditions.

Before deciding on a type of surgery, discuss the risks and benefits of each treatment option with your surgical team.

Preventative treatment for intracranial aneurysm

If you are diagnosed with an intracranial 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. Intracranial aneurysms that are located near larger blood vessels have a high risk of a rupture.
• Whether you have a family history of ruptured intracranial aneurysm.
• Whether you have an underlying health condition that increases the risk of a rupture, such as polycystic kidney disease.

Watchful waiting is usually recommended if the aneurysm is less than 3mm (0.1 inches) in diameter and there are no associated risk factors.

Surgery is usually recommended if the aneurysm is larger than 7mm (0.3 inches) in diameter or larger than 3mm (0.3 inches) and there are associated risk factors.

Watchful waiting

If watchful waiting is recommended, you will 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. You will probably be asked to make the same lifestyle changes that are outlined above, such as losing weight and reducing the amount of fat in your diet.

Surgery

Two surgical techniques have proved to be successful in the treatment of intracranial aneurysms: neurosurgical clipping and endovascular coiling.

Neurosurgical clipping

Neurosurgical clipping is a procedure that is carried out under general anaesthetic (you are asleep). An incision (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 a plastic tube, or catheter, being inserted 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.

Clipping or coiling?

Both coiling and clipping carry their own set of advantages and disadvantages.

As clipping is invasive surgery, the risks of complications and death during or shortly after surgery are greater. It is estimated that between 4 and 10% of people undergoing clipping will experience complications, and between 1 and 3% of people will die.

In comparison, an estimated 3 to 5% of people undergoing coiling will experience complications, and 1 to 1.5% will die.

However, as clipping seals the aneurysm, rather than just blocking the flow of blood, it is thought to be more effective in preventing ruptures in the long-term.

There is considerable debate within the medical community about which is the most effective treatment and, as yet, no consensus has been reached.

Before deciding on a particular type of surgery, discuss the risks and benefits of each procedure with your surgical team.

Emergency treatment

Emergency treatment is based on the same principles as preventative treatment. Grafts are used to repair ruptured aortic aneurysms, and coils or clipping are used to repair ruptured intracranial aneurysms.

Additional medications 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.

While not all the risk factors for aneurysms can be prevented, the three leading risk factors can. These are:

• smoking,
• atherosclerosis (narrowing of the arteries), and
• high blood pressure (hypertension).

Smoking

Smoking is a major risk factor for aneurysms because it causes atherosclerosis and raises your blood pressure. Smokers are four times more likely to develop an aneurysm than non-smokers.

If you want to give up smoking a good first step is to contact Smokers Helpline Wales on 0800 169 0 169 and Stop Smoking Wales on 0800 085 2219.  Stop Smoking Wales hold details of local support services.  These services offer the most effective support for people who want to give up smoking. Studies show you are four times more likely to give up smoking successfully if you do it with the help of the NHS.

Alternatively, your GP or pharmacist can provide help and advice about quitting.

Atherosclerosis

As well as smoking, one of the leading causes of atherosclerosis is eating a diet that is high in fat.

High fat foods can cause a build up of fatty plaques in your arteries. This is because fatty foods contain cholesterol. There are two main types of cholesterol:

• Low-density lipoprotein (LDL). This is mostly made up of fat, plus a small amount of protein. This type of cholesterol can block your arteries, so it is often referred to as bad cholesterol.
• High-density lipoprotein (HDL). This is mostly made up of protein, plus a small amount of fat. This type of cholesterol can reduce any blockage in your arteries, so it is often referred to as good cholesterol.

There are also two types of fat: saturated and unsaturated. Avoid food containing saturated fats because these will increase the levels of bad cholesterol in your blood.

Foods high in saturated fat include:

• meat pies,
• sausages and fatty cuts of meat,
• butter,
• ghee (a type of butter often used in Indian cooking),
• lard,
• cream,
• hard cheese,
• cakes and biscuits, and
• foods that contain coconut or palm oil.

However, eating a small amount of unsaturated fat will increase the level of good cholesterol and help reduce any blockage.

Foods that are high in unsaturated fat include:

• oily fish,
• avocados,
• nuts and seeds, and
• sunflower, rapeseed and olive oil

High blood pressure

The best way to prevent high blood pressure is to eat a healthy diet, maintain a healthy weight, exercise regularly, drink alcohol in moderation and avoid smoking.

Diet

A low-fat, high-fibre diet is recommended, including plenty of fresh fruit and vegetables (five portions a day) and whole grains. Llimit the amount of salt that you eat to no more than 6g (0.2oz) a day because too much salt will increase your blood pressure. About one teaspoonful of salt is equal to 6g.

Weight

Being overweight is a risk factor for having high blood pressure and your risk is increased further if you are obese.

The most scientific way to measure your weight is to calculate your Body Mass Index (BMI). This is your weight in kilograms divided by your height in metres squared. In the UK, people with a BMI from 25 to 30 are overweight, and those with an index above 30 are classed as obese. People with a BMI of 40 or more are morbidly obese.

The best way of losing weight if you are overweight is to reduce the amount of calories that you eat, and ensure that you take regular exercise. Your GP can provide you with further information and advice about how you can do this.

Exercise

Regular exercise will make your heart and blood circulatory system more efficient. It will help to lower your cholesterol level and keep your blood pressure at a healthy level.

For most people, 30 minutes of vigorous exercise a day, at least five times a week, is recommended. The exercise should be strenuous enough to leave your heart beating faster, and you should feel slightly out of breath afterwards. Examples of vigorous exercise include going for a brisk walk and walking up a hill.

Alcohol

Drinking excessive amounts of alcohol will cause a rise in your blood pressure, and it will also raise the cholesterol levels in your blood.

Sticking to the recommended limits of alcohol consumption is the best way to ensure that you reduce the risk of high blood pressure and aneurysms.

The recommended daily levels of alcohol consumption are three to four units of alcohol for men, and two to three units for women. A unit of alcohol is equal to about half a pint of normal strength lager, a small glass of wine, or a pub measure (25ml) of spirits.