Daniel Walsh, Consultant Neurosurgeon


Aneurysmal 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. Trauma to the head may also produce such bleeding so when the bleeding may be attributed to a leaking aneurysm it is aneurysmal subarachnoid haemorrhage (aSAH). Less commonly a blood clot may collect within the brain tissue itself.

What are the symptoms of aSAH?

In most patients aSAH produces a very characteristic collection of symtoms which will be recognisable to medical staff. These consist of:

  • A sudden-onset of severe headache- often the worst headache the patient has ever experienced.
  • Nausea with or without vomitting
  • Neck stiffness
  • Sensitivity to light
  • Reduced conciousness

In severe cases the patient may lose concsiousness completely. There is usually little doubt that the affected induvidual is unwell and in need of medical attention.

Aneurysmal subarachnoid haemorrhage is a medical emergency and such symtoms should prompt urgent investigation. There are rare cases where patients present with less severe headache . "Herald" headaches have been reported ahead of aneurysm rupture and these are thought due to sudden enlargement ahead of rupture of the aneurysm. These may occur shortly before rupture in a minority of cases.

It is sometimes difficult to distinguish these from more common and benign types of headache. Occasionally an aneurysm close to a nerve which controls movement of the eyeball will enlarge suddenly without actually leaking. This can produce pain behind the eye, double vision and irregularity of the pupils. This is considered an emergency as well as it may warn of an unstable aneurym liable to bleed in the short term.

What Tests will be Required?

CT angiogram showing ruptured left middle cerebral artery aneurysm and temporal haematomaA 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 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 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. This is a very sensitive test for even small amounts of blood. If negative thenaSAH can be confidently ruled out in the two weeks after the headache.

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 the aneurysm causing the symptoms. It may even provide sufficent information to allows 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.

In about 10% of subarachnoid haemorrhage we do not find any undrlying structural cause. In such a case angiography is usually repeated after a short interval. The outlook in these cases is excellent and further bleeding is extremely rare. It is however important that a thorough search is made for an aneurysm or other source of bleeding as a vascular malformation.


How is aSAH treated?

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 diagnosis. Rarely it will be recommended that treatment wait on a patient's further recovery. Your neurosurgeon willl discuss the reasons for any deferral.

Most ruptured aneurysms in the United Kingdom are currently treated by placement of tiny platinum coils inside the aneurysm. Some aneurysms are better treated by a microsurgical procedure to place a small clip remove the aneurysm from the circulation. You can learn more about how aneurysms are repaired here.

Making the aneurysm safe is a very important first step but does not represent the end of this illness. Most patients can expect to be in hospital for between 7 and 14 days.


What other problems can develop?

Apart from further aneurysm bleeding there are several other complications which may develop in the days following a subarachnoid haemorrhage:

3D digital subtraction angiogram of middle cerebral artery aneurysmPart of the danger lies in the risk of further bleeding occurring from the aneurysm. Consequently the aim is to make the aneurysm safe by endovascular or microsurgical repair as soon as possible. There are some occasions with very complex aneurysms, requiring especially complex treatments, when it may be decided to wait some time to allow the brain to recover and the patient's condition to stabilise. Rebleeding will occur in at least 3-4% of patients within 24 hours of their first haemorrhage. Thereafter there is a risk of rebleeding of 1-2% per day. The risk is believed to reduce to about 3% per year after 3 months.

One of the effects of SAH is to impair its ability to regulate the delivery of oxygen to the brain. The blood vessels normally entrusted with this task lose the ability to ensure a constant supply of oxygen to the brain and this is termed delayed cerebral ischaemia (DCI). Doctors sometimes refer to vasospasm where the larger vessels develop a narrowed appearence on an angiogram.This state may persist for approximately 10 to 14 days after the bleeding and during this time the patient is at significant risk of suffering stroke. Although the causes of DCI are yet to be fully understood there are a number of treatments which help mitigate its effects. The team treating you or your relative will be happy to discuss these with you.

Stroke during this period of the illness is one of the most important causes of disability following SAH. The term stroke, as used here, refers to the effect of depriving living tissue in the brain of oxygen. This tissue may die as a result and the loss of its function translates as the disability experienced by the patient.

The brain produces cerebrospinal fluid (CSF) that normally circulates around the nervous system buffering and protecting it. If the normal routes of CSF flow are obstructed, for example by blood clot, fluid may build up within the ventricles of the brain and increase the pressure within the head. After SAH this occurs at two points: Early after the initial bleeding because of mechanical obstruction of the flow of CSF by blood clot. There is a second peak in occurrence later on because of damage to the normal production and reabsorption apparatus of the CSF.

Hydrocephalus may be treated by:

  • Temporary measures to divert the CSF e.g. lumbar puncture (spinal tap), lumbar drains or ventricular drains placed through a small surgical incision.
  • Permanent CSF diversions e.g. Ventriculo-peritoneal shunt- an operation is carried out to place a tube draining fluid from the brain , tunnelled under the skin down to the abdomen where the tube drains into the tummy. the rate of flow is controlled by a small valve device placed at the same time.


Are there long term consequences of aSAH?

Stroke and the consequent disability complicates bout 30% of cases of subarachnoid haemorrhage. There is a great deal of variation in how serious physical disability is dependent of the areas of the brain that are affected.

Patients who make an excellent physical recovery often report a variety of non-specific or psychological symptoms that may last many months after the inital haemorrhage. These include:

  • Fatigue. Severe tiredness is very common in the weeks and months after aSAH. This can limit normal activities such as going to the shops or socialising. Despite this fatigue it may be difficult to sleep. Your doctors may wish to check hormone levels and blood chemistry. You may find yourself more affected than previously by very stimulating enviroments where a lot of people approach you at once and dealing with more than one task at a time can be difficult. Bright lights and noisy enviroments may be difficultand you may find yourself more afffected by alcohol than before. It will help to build up activity gradually. and in time these problems improve for most patients.

  • Memory Problems. Patients often have little recollection of the time they were in hospital, especially if the haemorrhage has been severe. Some patients will experience difficulty with short-term memory in particular. This will often improve over time and can often be helped by adopting aids such as keeping a small notebook of reminders. Your doctors will want to exclude the late development of hydrocephalus as a cause (see above). It can make returning to work difficult as remembering multiple steps which enables dealing with complicated tasks is a problem. Concentrating may be difficult and it may help to break tasks down into small steps each to be completed one at a time. Returning to work in a phased fashion may help facilitate this and it is useful to speak to an employer as to how this may be accomplished.

  • Mood problems. It is common to experience lability in mood. People can experience periods of low mood and may find themselves more tearful often for no apparent reason. Some report they have developed a shorter temper. In contrast some become more patient or tolerant. The reasons for this are probably complex, combining physical consequences of the haemorrhage on the brain with the psychological impact of experiencing a major life event. A few experience periods of profound sadness which become disabling. These are symptoms of depressive illness and your family practitioner ot a clinical psychologist can discuss appropriate treatments which are likely to help.