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Haemorrhage, brain Content Supplied by NHS Choices

A subarachnoid haemorrhage is a type of stroke caused by bleeding in and around the brain.

Subarachnoid haemorrhages account for around 1 in 20 of all strokes in England

The most common symptom of a subarachnoid haemorrhage is a sudden and very severe headache which has been described as 'like being hit on the head with a shovel'.

Other symptoms can include:

  • being sick
  • seizures (fits)
  •  loss of consciousness
  • sudden death (in about 1 in 10 cases)

Read more about the symptoms of a subarachnoid haemorrhage.


Subarachnoid haemorrhage is a medical emergency that requires immediate treatment.

If you or someone you know thinks a subarachnoid haemorrhage has occurred you should immediately dial 999 for an ambulance.

A person with a subarachnoid haemorrhage will need to be admitted to hospital.

There are two main treatment approaches:

  • using medication to prevent complications (see below)
  • using surgery to repair the source of the bleeding

Read more about treating a subarachnoid haemorrhage.

What causes a subarachnoid haemorrhage?

The majority of subarachnoid haemorrhages are caused when a brain aneurysm bursts open. A brain aneurysm is a bulge in a blood vessel  caused by a weakness in the blood vessel wall. (The medical term for a burst brain aneurysm is a ruptured intracranial aneurysm.)

The blood from a burst aneurysm can damage brain tissue, while the reduction in blood supply can starve the brain of oxygen causing further damage.

It is not always clear why aneurysms develop in the first place but certain things are known to increase your risk of developing one, including:

Read more about the causes of a subarachnoid haemorrhage.


A subarachnoid haemorrhage can cause both short and long-term complications.

Serious short-term complication include:

  • further bleeding at the site of the aneurysm
  • blood vessels near the site of the aneurysm go into spasm (vasospasm) reducing the blood supply further 

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.

Who is affected 

There are up to 9,000 hospital admissions for subarachnoid haemorrhages each year in England.

Four out of five cases occur in people aged between 40 and 65 years, but it can happen at any age; although it is rare in children.

It is more common in women than men.

Subarachnoid haemorrhages are more common in black people compared to other ethnic groups. This could be because black people are more likely to develop high blood pressure. (Read more about black health issues).


The outlook for subarachnoid haemorrhage has improved in the last few decades, and about 65% of patients will survive. However, recovery can be a slow and often frustrating process and it is common to have difficulties with issues such as relationships and resuming day to day activities 

Read more about recovering from a subarachnoid haemorrhage.

To haemorrhage means to bleed or lose blood.
Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
Blood vessels
Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Body tissue is made up of groups of cells that perform a specific job, such as protecting the body against infection, producing movement or storing fat.