Subarachnoid Haemorrhage


Subarachnoid Haemorrhage is the sudden leaking (haemorrhage) of a blood vessel over the surface of the brain. The brain is covered by a series of membranes, one of which is called the arachnoid. A subarachnoid haemorrhage occurs under this layer. It is one form of stroke. (See Stroke)

The most common sign of a subarachnoid haemorrhage is severe headache, often at the back of the head, followed by nausea and vomiting. Neck stiffness is also common. In the most severe cases (about 30-40%) the person may lose consciousness, and some (about 10%) may have a seizure (fit). The headache usually starts very suddenly (like a ‘blow to the head’), and within seconds becomes the most intense headache the patient has ever felt.

After minutes to hours the headache spreads to the back of the head, neck and back as blood tracks down the spinal subarachnoid space.

In most cases subarachnoid haemorrhage is due to a weakness in the wall of one of the arteries to the brain.  The balloon-like swelling is called an aneurysm (see also “Aneurysm”). The haemorrhage occurs when the wall of the aneurysm tears because of the pressure of the blood. A subarachnoid haemorrhage also can occur because blood leaks from an abnormal tangle of blood vessels called an arteriovenous malformation (AVM) (see also “Arteriovenous Malformation”).

The reasons for the development of aneurysms are not understood, but they occur more often in people with high blood pressure and people who smoke. They are more common in women and in older people, but in general occur at a younger age than strokes due to blocked arteries. Occasionally there is a family history.


A subarachnoid haemorrhage is an emergency and the patient must be taken to hospital immediately. Scanning and an angiogram (a test in which a fine tube is passed through an artery in the groin up to the arteries supplying blood to the brain) will show the precise location of the haemorrhage. Surgery to repair the damaged blood vessel will be carried out at a time best suited to the condition of the individual patient (some aneurysms can be treated via angiography, with the insertion of platinum coils to fill the aneurysm). The purpose of the operation or coiling is to prevent further haemorrhages.

The other main complication is delayed spasm of the blood vessels, which may occur a week or more after the haemorrhage and can cause permanent or fatal strokes. Other complications of the bleed or the surgery may remain for a period after the operation – difficulty in opening the jaw, headaches, pain or numbness round the scar – but these should gradually decrease.

Occasionally epileptic fits may occur, but these can be controlled with medication. Sometimes there is a build-up of the fluid in and around the brain and spinal cord (hydrocephalus); this causes generalised headache and problems with higher mental functions and memory and with balance. A small operation to insert a tube (shunt) can be performed to drain the excess fluid.


  • to reduce the risk of contraction of blood vessels leading to stroke
  • to control fits
  • to lower blood pressure

will be prescribed as necessary in individual cases, as well as painkillers such as codeine and paracetamol.


Aneurysm rupture is very dangerous, being fatal in 40% or more, with stroke-like deficits in half the remainder – in these the damage to brain tissue caused by the original haemorrhage or delayed blood vessel spasm may cause speech disturbance, weakness down one side of the body or double vision.

Not all such damage is permanent however, and intensive rehabilitation, with physical, occupational and speech therapy will help recovery – which may be slow and uneven.

Patients in the immediate aftermath of a subarachnoid haemorrhage  should not

  • smoke
  • drive until given permission to do so by their doctor
  • climb ladders, swim unaccompanied or do other activities which may be dangerous if they have a fit.

Patients should gradually be able to resume their normal lives as they feel able to do so. Any doubts (such as when to return to work, or the advisability of resuming sporting activities) should be discussed with the doctor. It is essential to maintain a regimen of regular exercise, and continue medication as advised by the doctor, especially if treatment for high blood pressure is needed.

About 10% of strokes are due to subarachnoid haemorrhage. Recurrence is unlikely once the aneurysm has been treated. Patients can now be checked from time to time with special CT or MRI scans to make sure they do not develop further aneurysms. This service is also available to relatives where there is a family history of aneurysms.

Further Information and Support

Click here for the latest Australian research papers on Subarachnoid Haemorrhage.


National Stroke Foundation (with information on support services throughout Australia)



Reviewed by Professor Nicholas Dorsch, Department of Neurosurgery, Westmead Hospital

DISCLAIMER: The information provided is designed to support, not replace, the relationship that exists between a patient / site visitor and his / her existing health care professionals.

Brain FoundationThe Brain Foundation is the largest, independent funder of brain and spinal injury research in Australia. We believe research is the pathway to recovery.