Introduction 

A subarachnoid haemorrhage is an uncommon type of stroke caused by bleeding on the surface of the brain. It is a very serious condition and can be fatal.

Subarachnoid haemorrhages account for around 1 in every 20 strokes in the UK.

The main symptom of a subarachnoid haemorrhage is a sudden and very severe headache that is often described as a blinding pain, unlike anything experienced before.

Other symptoms can include:

  • a stiff neck
  • being sick
  • sensitivity to light
  • blurred or double vision
  • seizures (fits) or loss of consciousness

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.

Read more about the symptoms of a subarachnoid haemorrhage.

How a subarachnoid haemorrhage is treated

A person with a suspected subarachnoid haemorrhage will need to have 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 are 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.

Read more about diagnosing a subarachnoid haemorrhage and treating a subarachnoid haemorrhage.

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, and is caused by a weakness in the blood vessel wall.

It is not known exactly why brain aneurysms develop in some people, although certain factors that increase your risk of the condition have been identified. These include:

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.

Who is affected

Between April 2012 and April 2013, over 11,000 people were admitted to hospitals in England with a subarachnoid haemorrhage.

Subarachnoid haemorrhages can happen at any age, even children, but they are 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:

Read more about preventing subarachnoid haemorrhages.

Possible complications

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.

Outlook

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, headaches and problems sleeping.

Read more about recovering from a subarachnoid haemorrhage.

Stroke: an animation

This animation explains how a stroke happens, the different types of stroke and how lifestyle changes may help to reduce the risks.

Media last reviewed: 14/11/2013

Next review due: 14/11/2015

Page last reviewed: 12/02/2014

Next review due: 12/02/2016