A subarachnoid haemorrhage is an uncommon cause of a stroke where blood leaks out of blood vessels over the surface of the brain. Like all strokes, a subarachnoid haemorrhage is a medical emergency that requires immediate treatment to prevent serious complications, brain damage and death.
It is known as a subarachnoid haemorrhage because the bleeding occurs in the arteries that run underneath a membrane in our brain called the arachnoid, which is just below the surface of the skull.
Three quarters of subarachnoid haemorrhages are caused when an aneurysm ruptures (burst). An aneurysm is a bulge in a blood vessel that is caused by a weakness in the blood vessel wall.
During a subarachnoid haemorrhage, the blood damages the brain tissue. The reduction of blood supply can also cause further brain damage, leading to disruption or loss of brain function and possibly death.
How common are subarachnoid haemorrhages?
Subarachnoid haemorrhages are uncommon, responsible for only 5% of all strokes. However, they are a leading cause of death, responsible for a quarter of all deaths related to strokes.
Every year around 8,000 people in the UK have a subarachnoid haemorrhage. It is more common in middle-aged people, and women are more likely to be affected than men.
Outlook
A subarachnoid haemorrhage is an extremely serious condition and for many people the outlook is poor. 10-15% of people with a subarachnoid haemorrhage will die before they can be admitted to hospital, and 50% will die within 30 days after the haemorrhage.
However, the prospects of recovery are good if the patient survives the initial bleeding and they are transferred quickly to a specialist neurosurgical unit (a medical unit that specialises in treating conditions of the brain and nervous system).
A number of surgical techniques have proved successful in treating subarachnoid haemorrhages. Following treatment, a long period of rehabilitation will be necessary.
