Subarachnoid Haemorrhage

When an aneurysm ruptures, blood leaks into the fluid which circulates around the brain,
the cerebrospinal fluid or CSF. This fluid is normally contained around the substance of the brain
by a thin layer of tissue that resembles a spider-web. This web-like tissue is termed the arachnoid layer.
This pattern of bleeding is therefore referred to as subarachnoid haemorrhage.

Signs and Symptoms of Rupture

Rupture is usually an unanticipated event. Most people who suffer one had no idea the aneurysm was present and there was no warning or precipitant. 80% of patients describe "the worst headache of my life". This is termed the ictal headache. This may be accompanied by nausea, voitting or alteration in conciousness. Most people developing a rupture are not engaged in strenuous activity at the time.

A minority of patients report headaches that precede an ictal headache by days or weeks. It has been suggested that such headache reflects changes in the shape or size of the aneurysm brought on by instability in its wall and foreshadowing rupture. The occurence of such sentinel headaches has been reported in 10-45% of patients who subsequnelty presented with a subarachnoid haemorrhage. It is difficult to be certain however that all were certainly predictive of subsequent aneurysm rupture and of course benign headaches are very common.

The development of focal neurological symptoms is a relatively rare presentation of aneurysms that are at risk of rupture and is described on the page covering other symptomatic aneurysms

Investigation and Treatment

Aneurysmal subarachnoid haemorrhage is a medical emergency and such symtoms should prompt urgent investigation. The nearest emergency department is the appropriate first call.

A Computerised Tomography or CT scan will confirm that a subarachnoid haemorrhage has occurred in most cases. This scan makes use of X-rays to build detailed pictures of the head or body.

From a few hours after the haemorrhage until about two weeks afterwards the blood may be relatively easily seen by a trained observer. Occasionally the amount of blood which has leaked into the cerebrospinal fluid (CSF) is very small and not possible to discern on the CT scan. In such cases a sample of the CSF should be taken from the small of the back under local anaesthetic (lumbbar puncture). This is a very sensitive test for even small amounts of blood. If negative then a SAH may be confidently ruled out in the two weeks after the headache. Beyond that time the diagnosis is more difficult to exlcude. MRI can demonstrate blood staining of the brain tissue but it is not as specific for an aneurysmal origin.

>Modern CT scanners can generate very detailed pictures of the blood vessels within the brain. This is called CT Angiography (CTA)and in most cases will demonstrate an aneurysm. It may even provide sufficent information to allow treatment to be planned and carried out. Some hospitals may prefer to make use of Magnetic Resonance Angiography (MRA).

The most detailed pictures of the blood vessels within the brain are obtained by a technique called Digital Subtraction Angiography (DSA). After a local anaesthetic injection a small tube is passed into a large artery at the top of the leg. Occasionally an artery at the elbow is used. Guided by x-rays the tube is directed into the blood vessls of the brain where dye is injected to produces very detailed pictures of the circulation. DSA is carried out by a specialist neuroradiologist who will discuss the potential risks of the procedure with the patient and/or their carers.

Once a ruptured aneurysm has been located repair is recommended to prevent further bleeding. Haemorrhage from an aneurysm is a life-threatening event. As many as 30% of patients suffering a first haemorrhage die as a result of the illness. If the aneurysm bleeds again the chance of dying rises to between 50 and 70%. We will usually endeavour to make the aneurysm secure within 24 hours of its diagnosis. Rarely it will be recommended that treatment wait on a patient's further recovery. Your neurosurgeon will discuss the reasons for any deferral.