CEREBRAL DISEASE

SUB-ARACHNOID HAEMORRHAGE

• INTRODUCTION
  

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 or layer in our brain called the arachnoid, which is just below the surface of the skull.

During a subarachnoid haemorrhage, the blood damages the brain tissue. The reduction of blood supply can also cause further brain damage, leading to disruption or loss of brain function and possibly death.

• SYMPTOMS
  

The common symptoms of a subarachnoid haemorrhage are:

• a sudden and severe headache - it has been described as similar to a sudden hit on the head, resulting in a blinding pain unlike anything ever experienced before,
• stiff neck,
• sickness and vomiting, and
• slurred speech.

Around 30-40% of people who have a subarachnoid haemorrhage will also experience impaired or total loss of consciousness.

Sometimes, the symptoms of a subarachnoid haemorrhage can be similar to meningitis (an infection of the nervous system) because in both conditions people experience a severe headache and a stiff neck.

Unlike meningitis, people with a subarachnoid haemorrhage will not usually have a high fever or have a rash on their skin. However, in either case, both conditions are extremely serious and emergency medical treatment should be sought straightaway.

• CAUSES
  

Blood circulation

Like all of the body's organs, the brain needs blood to provide it with oxygen and other essential nutrients.

Our circulation system is made up of arteries and veins. The blood is pumped from your heart, through the aorta (the main artery leading from the heart) before travelling through smaller and smaller arteries that branch off from each other. The blood passes into tiny vessels known as capillaries where the oxygen in the blood is transferred into the cells that make up our body's tissues and organs.

The capillaries then move the blood into our veins which carry it back to the heart. The veins are weaker and smaller than the arteries, so the capillaries must also reduce the speed and pressure of the blood.

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

Aneurysms

For reasons largely unknown, 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.

If a berry aneurysm bursts, a subarachnoid haemorrhage will occur. Not everyone who has a berry aneurysm will experience a haemorrhage. In fact, haemorrhages among people with berry aneurysms are very rare, occurring in about 1 in 700 people. However, smoking, excessive alcohol consumption and high blood pressure (hypertension) will increase the chances of an aneurysm bursting.

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

Arteriovenous malformations occur when the blood vessels develop abnormally. They affect approximately 1 in every 100 people and, although the exact cause is unknown, they are thought to be the result of a problem that occurs during the development of the foetus.

Arteriovenous malformations can occur anywhere in your body but they very rarely occur in the brain, with just 1 in every 10,000 people being affected.They can cause problems because they affect the way that blood is pumped around our body.

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.

• DIAGNOSIS
  

The initial diagnosis of a subarachnoid haemorrhage can be made through the characteristic symptoms of the condition, such as a severe headache and a stiff neck.

Following an initial diagnosis it is likely that you will be referred to a specialist neurosurgical unit for further tests to confirm the diagnosis and, afterwards, to decide on the best course of treatment.

The most common tests that are used for investigating cases of subarachnoid haemorrhage are outlined below.

Computerised tomography (CT) scan

A computerised tomography (CT) scan is like an X-ray, but it uses multiple scans or images to build up a more detailed three-dimensional picture of your brain. The scan can be used to detect the presence and location of blood around your brain and any problems that it may be causing. Sometimes a coloured dye is injected into the blood to help pinpoint the source of the bleeding.

Lumbar puncture

The brain and spinal column are surrounded by a clear liquid called cerebral-spinal fluid. If a subarachnoid haemorrhage has occurred there will be blood in the fluid. To get a sample of cerebral-spinal fluid, a needle is placed at the lower end of your spine and a sample is drawn off. You may find the procedure a little uncomfortable but you will be given a local anaesthetic to numb the area.

MRI scan

A magnetic resonance imaging (MRI) scan uses sound waves to build up a picture of the inside of your body. The scan can be used to detect problems in the blood vessels and, occasionally, even the haemorrhage itself.

• TREATMENT
  

After a subarachnoid haemorrhage occurs, some of the blood vessels near the burst aneurysm can then go into spasm. This can lead to a further loss of blood to the brain, causing brain damage.

To prevent this happening, you may be given a medication called nimodipine, which you will need to take for three weeks. Nimodipine was originally used to treat high blood pressure, but it was found to be more useful in preventing spasms. Side-effects of nimodipine include:

• sweating and flushing,
• nausea,
• swelling of the feet, ankles or legs, and
• stomach upsets.

Surgery

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.

However, it may be necessary to wait until you are healthy enough to undergo surgery. This could take from a few days, to a few months, depending on the severity of your haemorrhage.

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