What is a brain aneurysm?
A cerebral aneurysm is a balloon-like bulge that forms at a weak point in the wall of an artery supplying the brain. Most are small and cause no symptoms, and many are found incidentally on a scan performed for another reason. The concern with an aneurysm is that the thin wall may leak or rupture, causing bleeding around or into the brain (a subarachnoid haemorrhage), which is a medical emergency.
Having an aneurysm is not the same as being destined to have a bleed. Many aneurysms remain stable for life. The purpose of assessment is to estimate the risk of rupture for a particular aneurysm in a particular person, and to weigh that against the risks of treatment.
A sudden, severe headache unlike any before, often described as the worst headache of one's life, sometimes with neck stiffness, vomiting, light sensitivity or loss of consciousness, may indicate a ruptured aneurysm. Call 000 immediately.
Unruptured aneurysms and rupture risk
The risk that an unruptured aneurysm will bleed depends on several factors, including its size, its location in the circulation, its shape, whether it is growing, and personal factors such as smoking, blood pressure, family history and previous bleeding from a different aneurysm. Small aneurysms in low-risk locations often carry a very low annual rupture risk, and may reasonably be watched with interval imaging rather than treated.
Because both the condition and its treatment carry risk, the decision to treat or to monitor is individual. The aim is to intervene where the long-term risk of the aneurysm clearly outweighs the risk of the procedure, and to avoid treating aneurysms that are more safely observed.
How aneurysms are found and assessed
Aneurysms are identified and characterised with vascular imaging:
- CT angiography (CTA) and MR angiography (MRA), which provide detailed non-invasive images of the arteries
- Catheter angiography (DSA), the most detailed study, used to define the aneurysm precisely and to plan treatment
Assessment considers the size, neck, shape and branch anatomy of the aneurysm, all of which influence both rupture risk and the best treatment approach.
Treatment options
There are three broad pathways, and the right one depends on the aneurysm and the person.
Monitoring (surveillance)
For many small, stable, low-risk unruptured aneurysms, the safest approach is interval imaging to check for change over time, alongside management of blood pressure and stopping smoking. This is an active plan, not a failure to treat.
Endovascular treatment
Most aneurysms treated today are treated from within the artery, without open surgery. Working through a small puncture in the wrist or groin, a microcatheter is navigated to the aneurysm. Depending on its shape, treatment may involve:
- Coiling, in which fine platinum coils are packed into the aneurysm to seal it from the circulation, sometimes supported by a stent or balloon where the neck is wide
- Flow diversion, in which a fine mesh stent is placed across the neck of the aneurysm in the parent artery, redirecting blood flow so the aneurysm gradually thromboses and is remodelled out of the circulation
Surgical treatment
Microsurgical clipping, performed by a neurosurgeon, places a small clip across the neck of the aneurysm through an operation on the skull. It is a durable, well-established treatment and remains the better option for some aneurysms. Where surgery is preferable, care proceeds with neurosurgical colleagues.
Aneurysm treatment decisions are made together with neurosurgical and stroke colleagues. The recommended option reflects the anatomy of the aneurysm, your overall health, and the current evidence.
Arranging an appointment
A referral from your GP or specialist is required. If you have been told you have an aneurysm, please bring or forward any relevant imaging so it can be reviewed at your appointment.