A brain aneurysm can be identified before it ruptures using brain scans. It can then be treated surgically in one of two ways:

• Microvascular clipping

This involves brain surgery and a craniotomy, an operation that opens up the skull so that the surgeon can get direct access to the aneurysm. A microscope is used to see the details of the blood vessels and to clip off the blood supply that leads to the bulging blood vessel.

Once it has been surgically clipped, a brain aneurysm is considered dealt with and a successful operation then requires no long-term follow up.

• Endovascular coiling

This is a less invasive technique that does not involve a brain operation through the skull. Instead the surgeon puts a catheter into the artery through a point in the groin, and the tip is guided up to the aneurysm. A guide wire then takes a platinum coil into the ballooned artery so that blood clots there, effectively sealing off the affected vessel.

A brain aneurysm can re-form near to the site where a coil has been placed, so someone who has this second procedure will need long-term follow up with regular MRI scans. If the aneurysm does re-form, endovascular coiling can be repeated.