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Subarachnoid Haemorrhage

Subarachnoid Haemorrhage

A subarachnoid haemorrhage is a serious and potentially life-threatening condition where blood leaks out of blood vessels over the surface of the brain. It is known as a subarachnoid haemorrhage because the bleeding occurs in the arteries that run underneath a membrane called the arachnoid, which is just below the surface of the skull.


A subarachnoid haemorrhage is a serious condition, and 50% of people who suffer with this condition will be left severely disabled or die. However, the prospects of recovery are good if the patient survives the initial bleeding and they are transferred quickly to a specialist neurosurgical unit.


Subarachnoid haemorrhages are mainly caused by aneurysms and arteriovenous malformations, which are both defects or weaknesses in the blood circulation system.



Around 1 in every 100 people are born with defects affecting the blood vessels in their brain. Some of the blood vessels have a thinned and weakened wall, which bulges outwards like a balloon when the blood runs through them. These are known as berry aneurysms.


Around 70% of subarachnoid haemorrhages are caused by aneurysms. After it has burst, the aneurysm will often seal itself and the bleeding will stop. However, there is a high risk that without treatment the aneurysm will burst again and cause more bleeding.


Arteriovenous malformations (AVM)

Arteriovenous malformations occur when blood vessels develop abnormally anywhere in the body and just 1 in every 10,000 people are affected by this condition developing in the brain.


In people with arteriovenous malformations there can be a direct connection between the arteries and the veins, without the capillaries to reduce the speed and pressure of the blood. This can cause the veins to expand and, in the case of a subarachnoid haemorrhage, split and bleed.

Most people with an arteriovenous malformation in the brain experience no symptoms until a haemorrhage occurs. Arteriovenous malformations cause around 10% of subarachnoid haemorrhages.


Treatment options

Following a subarachnoid haemorrhage, surgery should ideally be carried out as quickly as possible. This is because after an aneurysm has burst, there is an increased chance that it will do so again.

Two surgical techniques have proved to be successful in the treatment of subarachnoid haemorrhages - neurosurgical clipping and endovascular coiling.


Neurosurgical clipping

Neurosurgical clipping is a procedure that is carried out under general anaesthetic. During the procedure, an incision is made in your scalp and a small flap of bone is removed to reveal your brain below.


The surgeon will then carefully search for the aneurysm and, after locating it, seal it shut using a tiny metal clip. After the 'bone flap' has been replaced the surgeon will stitch the scalp back together.

Clipping has a relatively good success rate, with 70% of people making a significant or full recovery.


Endovascular coiling

Endovascular coiling is a procedure, which involves a plastic catheter being inserted into an artery through the leg or groin. The tube is then guided through the network of your blood vessels into the head and finally into the aneurysm. Tiny platinum coils are then passed through the tube into the aneurysm. These coils block the flow of blood into the aneurysm and so prevent further haemorrhaging.


Endovascular coiling is an increasingly popular treatment option, as it has a high success rate, with 77% of people making a significant improvement or a full recovery. This procedure is also less invasive compared to conventional clipping and recovery times are usually quicker.


Gamma Knife


Stereotactic radiosurgery with the use of a Gamma knife has the advantage of being a minimally invasive radiotherapy procedure to reduce the risk of an AVM re-bleeding. A Gamma-Knife is not actually a knife in the conventional sense, as it uses a focused array of intersecting beams of gamma radiation to gradually obliterate an abnormality, such as an AVM. This procedure is most effective on small lesions; where commonly a 90% obliteration rate can be expected following treatment.



Embolisation involves injecting resinous material, which then solidifies into the feeding vessels of an AVM. This technique tends to be used for small AVMs or to assist in the reduction of the size of a malformation. This procedure can be useful to shrink a malformation prior to Gamma Knife treatment.


The London Brain Centre has a rapid access facility with 24 hour cover for any patient or patients GP who wish to organise an urgent referral for investigation.


The London Brain Centre team are also available to offer 2nd opinion or take over the case of any patient, where advanced resources and technology to deliver optimum care to patients suffering with Aneurysms or Arteriovenous Malformations would be of value.


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Brain and neurology guide: conditions and treatments