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.
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.
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.
Exactly what causes the wall of affected blood vessels to weaken is still unclear though a number of risk factors have been identified.
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.
Only around 1 in 12,500 people will have a ruptured brain aneurysm in any given year in England.
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:
- eating a high-fat diet
- not exercising regularly
- being overweight or obese
Read more about preventing aneurysms.
- An aneurysm is a blood-filled sac that forms in a weakened part of a blood vessel.
- Arteries are blood vessels that carry blood from the heart to the rest of the body.
- 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.
- The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
- Congenital means a condition that is present at birth- the condition could be hereditary or develop during pregnancy.
- 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.
- 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.