Some information about subarachnoid haemorrhage
Most strokes happen because of a blockage in an artery leading to the brain, however about 20% are due to bleeding in or around the brain. A suarachnoid haemorrhage is when there is bleeding over the surface of the brain and 5% of strokes happen in this way. This factcheet explains how a subarachnoid haemorrhage happens and how it is diagnosed and treated.Each year, about 8,000 people in the UK have a subarachnoid haemorrhage (SAH), a bleeding over the surface of the brain. It is more common in middle-aged people, and women are more likely to be affected than men.
The brain itself is protected by a series of membranes, which lie beneath the bony skull. One layer is called the arachnoid membrane, and beneath it lie blood vessels which supply the brain. Blood vessel walls are always more fragile at places where they branch, and those in the brain have particularly thin walls. At branch-points, the vessel may start to bulge like a balloon – called an aneurysm – under the pressure of blood passing through. Eventually the aneurysm may burst, and blood leaks into the area beneath the arachnoid membrane – a subarachnoid haemorrhage.
Symptoms
The most common symptom is a sudden, severe headache, often followed by a loss of consciousness. Some people are also sick or have a stiff neck. Such symptoms can be easily confused with other, less serious conditions such as migraine. The stiff neck may also suggest meningitis. The suddenness and severity of the headache point to SAH, and it is essential to get immediate medical help.Diagnosis and treatment
SAH can only be diagnosed in hospital. A brain scan can indicate blood around the brain, while a lumbar puncture - a procedure to remove a sample of the cerebrospinal fluid that bathes the brain and spinal cord – will show if blood has leaked into the fluid. An angiogram is usually performed to locate the burst blood vessel. A fine tube called a catheter is put into an artery through which a dye is injected. X-rays then show the position of the aneurysm.Treatment has two primary aims – to seal off the burst aneurysm and to prevent spasm in nearby blood vessels, which could starve the brain of oxygen.
Surgery
An operation to seal off the aneurysm requires transfer to a specialised neurosurgical unit. Sometimes the operation can be done within a day or so of the SAH, but surgeons usually wait until unconscious or semi-conscious patients are more stable before operating. Waiting too long may increase the risk of another haemorrhage, but operating on a weakened patient may be fatal. SAH surgery takes about two to three hours and is carried out under general anaesthetic. There are several options.Open surgery involves opening the skull and making an incision in the membranes which protect the brain to get to the burst blood vessel. The surgeon will then put a metal clip around the neck of the aneurysm so that no more blood can escape.
Another option is to put a fine piece of platinum wire, read more
