A subarachnoid haemorrhage is an uncommon type of stroke caused by bleeding on the surface of the brain. It's a very serious condition and can be fatal.
Subarachnoid haemorrhages account for around 1 in every 20 strokes in the UK.
Symptoms of a subarachnoid haemorrhage
There are usually no warning signs but a subarachnoid haemorrhage sometimes happens during physical effort or straining – such as coughing, going to the toilet, lifting something heavy or having sex.
The main symptoms of a subarachnoid haemorrhage include:
- a sudden agonising headache – which is often described as being similar to a sudden hit on the head, resulting in a blinding pain unlike anything experienced before
- a stiff neck
- feeling and being sick
- sensitivity to light (photophobia)
- blurred or double vision
- stroke-like symptoms – such as slurred speech and weakness on one side of the body
- loss of consciousness or convulsions (uncontrollable shaking)
A subarachnoid haemorrhage is a medical emergency. Dial 999 immediately and ask for an ambulance if you, or someone in your care, has these symptoms.
How a subarachnoid haemorrhage is treated
A person with a suspected subarachnoid haemorrhage needs a computerised tomography (CT) scan in hospital to check for signs of bleeding around the brain.
If a diagnosis of subarachnoid haemorrhage is confirmed or strongly suspected, you're likely to be transferred to a specialist neurosciences unit.
Medication will usually be given to help prevent short-term complications (see below) and a procedure to repair the source of the bleeding may be carried out.
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What causes subarachnoid haemorrhages?
The majority of subarachnoid haemorrhages are caused by a brain aneurysm bursting. A brain aneurysm is a bulge in a blood vessel, caused by a weakness in the blood vessel wall.
It's not known exactly why brain aneurysms develop in some people. However, certain risk factors have been identified, including:
Less common causes of subarachnoid haemorrhages include having abnormally developed blood vessels and inflammation of blood vessels in the brain.
Severe head injuries often cause subarachnoid bleeding, but this is a separate problem known as a "traumatic subarachnoid haemorrhage".
Read more about the causes of subarachnoid haemorrhages.
Between April 2013 and April 2014, more than 6,000 people were admitted to hospitals in England with a subarachnoid haemorrhage.
Subarachnoid haemorrhages can happen at any age but they're most common in people aged between 45 and 70. Slightly more women are affected than men.
Subarachnoid haemorrhages are also more common in black people compared to other ethnic groups. This could be because black people are more likely to have high blood pressure. Read more about black health issues.
Reducing your risk
It's not always possible to prevent a subarachnoid haemorrhage, but there are some things you can do to reduce your risk.
The three most effective steps you can take to reduce your chances of having a subarachnoid haemorrhage are:
A subarachnoid haemorrhage can cause both short and long-term complications.
Serious short-term complications can include further bleeding at the site of any aneurysm and brain damage caused by a reduction in blood supply to the brain.
Long-term complications include:
- epilepsy – where a person has repeated seizures (fits)
- problems with certain mental functions, such as memory, planning and concentration
- changes in mood, such as depression
Read more about the complications of a subarachnoid haemorrhage.
Although the outlook for subarachnoid haemorrhage has improved in the last few decades, around half of all cases are fatal, and people who survive can be left with long-term problems.
Recovering after a subarachnoid haemorrhage can also be a slow and frustrating process, and it's common to have problems such as:
- extreme tiredness
- problems sleeping
Read more about recovering from a subarachnoid haemorrhage.