Overview
A brain aneurysm is a bulge or ballooning in a blood vessel in or around the brain. Most never cause symptoms and are found incidentally on scans. However, if one ruptures it causes a subarachnoid haemorrhage, a sudden, catastrophic bleed into the space around the brain.
How common is it?
Brain aneurysms affect around 1 in 50 people, though most never rupture. About 9,000 people in the UK have a ruptured brain aneurysm each year.
Causes and risk factors
Aneurysms form where artery walls are weak, often at branch points of blood vessels at the base of the brain. Factors that damage or stress artery walls increase risk.
Common risk factors
- High blood pressure
- Smoking
- Family history of brain aneurysm
- Female sex (more common in women over 40)
- Certain inherited connective tissue conditions
- Polycystic kidney disease
- Previous head trauma
Symptoms
- Most unruptured aneurysms cause no symptoms
- Sudden severe headache described as the worst of your life (ruptured aneurysm)
- Neck stiffness and sensitivity to light after sudden headache
- Nausea and vomiting with severe headache
- Vision changes or double vision (if pressing on a nerve)
- Loss of consciousness or seizure
When to see a doctor
Call 999 immediately for a sudden, severe, unexpected headache unlike any you have had before. This is a medical emergency. Also seek urgent assessment for sudden vision changes or a drooping eyelid with a dilated pupil.
Diagnosis
CT scan of the head is the first-line test for suspected rupture. Lumbar puncture is done if CT is negative but suspicion remains. MRI angiography or CT angiography visualises unruptured aneurysms.
Treatments
Endovascular coiling
Thin coils are inserted via a catheter through the groin artery into the aneurysm, promoting clot formation inside it and preventing blood from entering. Minimally invasive.
Surgical clipping
A metal clip is placed at the base of the aneurysm during open brain surgery, blocking blood flow into it. More invasive but highly durable.
Monitoring for small unruptured aneurysms
Very small aneurysms under 7mm with no symptoms are often monitored with regular MRI scans, as the risks of treatment may outweigh the risk of rupture.
Self-care and lifestyle
- Controlling blood pressure is the most important step to reduce rupture risk
- Stop smoking immediately
- Avoid intense straining such as heavy lifting or vigorous nose-blowing
- Discuss whether family members should be screened if you have a family history
Prevention
Not smoking, maintaining normal blood pressure, and limiting alcohol reduce aneurysm formation risk. Screening is offered to close relatives of people who have had subarachnoid haemorrhage in some centres.