If 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.
Aneurysm Rupture
Rupture of an aneurysm typically happens without warning. Most people who suffer one had no idea the aneurysm was present and there was no warning or precipitant.
Symptoms of Aneurysm Rupture
80% of those experiencing a ruptured aneurysm describe "the worst headache of my life". This is termed the ictal headache. This may be accompanied by nausea, vomitting or alteration in conciousness. Most people developing a rupture are not engaged in strenuous activity at the timeMilder headaches that precede the ictal headache by days and weeks are quite often recalled. It has been suggested such headaches reflect changes that foreshadow the aneurysms rupture. The occurence of such sentinel headaches has been reported in 10 to 45% of those presenting to hospital with subarachnoid haemorrhage. However benign headaches are much more common than brain aneurysm rupture and therefore it is very difficult to be certain in retrospect that such headaches were truly indicative of an impending aneurysm rupture. Focal neurological symptoms (stroke like symptoms) in the absence of headache is a very rare presentation of aneurysm rupture. It is most commonly associated with enlargement of aneurysms adjacent to sensitive structures or in very large aneurysms before they rupture. It is considered in the section covering other symptomatic aneurysms.
Investigations
Aneurysmal subarachnoid haemorrhage is a medical emergency and suggestive symptoms should prompt urgent investigation. The nearest emergency department is the appropriate first call.
The criterion standard to confirm subarachnoid haemorrhage is to take a sample of the cerebrospinal fluid and examine it for the presence of blood. A sample may be obtained by passing a needle into the subarachnoid space under local anaesthesia, usually in the small of the back. This is a lumbar puncture. Although the scans described below are sufficient in most cases to confirm subarachnoid haemorrhage, lumbar puncture continues to have an important role in cases where there is doubt and may prevent a life threatening diagnosis being missed.
CT Imaging
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. The image on the right shows a CT slice through the head and the fresh bleeding is visible as the white star like appearance projecting in multiple directions from the centre of the brain. The clotted blood is more dense than the cerebrospinal fluid normally occupying these spaces and so the x-rays find it more difficult to pass through. Very dense tissue such as bone appears uniformly white while air which the x-rays pass through unhindered appears black.
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. In the illustration (below) a three dimensional image of a complex aneurysm is shown before and after microsurgical clipping.
MR Imaging
Magnetic resonance imaging (MRI) creates images without the use of ionising radiation. Put most simply this technology collects information about the relative water content of different tissues and the application of radiofrequency pulse allows manipulations of that data to examine particular tissue components.
Some hospitals may prefer to make use of Magnetic Resonance Angiography (MRA) to image the vessels themselves but MRI is not usually favoured to make the initial diagnosis by detecting the presence of blood. The logistics of placing a seriously unwell person in the MR environment mean that it takes longer and may be a less safe environment without any particular advantages in establishing the diagnosis. Interpretation of the imaging is also less straightforward as MR is very sensitive to short term changes in the make of blood in the hours and days following haemorrhage.
MR imaging may play a role evaluating a "missed haemorrhage" outside of the window when CSF examination could confidently exclude it but usually in providing indirect evidence of previous bleeding such as by demonstrating blood product staining of brain tissue. Vessel wall enhancement is an MR technique with potential to distinguish aneurysms at high-risk of bleeding. However it is a research tool at present as work proceeds to validate and improve its specificity. At present it should not be relied upon to determine if an unruptured aneurysm is at hight risk of bleeding and requires treatment.
Digital Subtraction Angiography
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 wrist, elbow or neck 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. Any further bleeding from the aneurysm is associated with a significantly increasing risk to life.
Consequences of Aneurysm Rupture
Aneurysm rupture is a serious illness and a medical emergency. 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. Occasionally it will be recommended that treatment wait on a patient's further recovery. Your neurosurgeon will discuss the reasons for any deferral. Securing the aneurysm from further bleeding is a very important first step but may not be the end of the illness triggered by rupture.
Many people have relatively little recall of the first days and weeks following a severe haemorrhage even with an ultimately excellent clinical outcome. The aftermath of subarachnoid haemorrhage may include the following:
Hydrocephalus- a disorder of the production and/or circulation of cerebrospinal fluid (CSF). While common in the early phase after rupture it is frequently self-limiting although a temporary surgical bypass of the fluid may be required. For a minority of people there may persist an imbalance between the production of CSF and its usual reabsorption into the bodies circulation requiring a permanent CSF diversion e.g. a ventricle-peritoneal shunt. Left untreated the gradual buildup of fluid may adversely affect eyesight, balance, intellectual function and memory amongst other things.
Delayed Cerebral Ischaemia- is a phenomenon where the provision of adequate blood flow to the brain becomes disordered. The inability to adjust to change in demand place makes the brain vulnerable to stroke through lack of sufficient oxygen. This is most common between 4 and 10 days following the aneurysm rupture.
Metabolic Disorders- the most common of these result in excessive excretion of salt and water from the body producing a low serum sodium level (hyponatraemia).
Cognitive Problems- even temporary reductions to blood flow in critical parts of the brain may leave a long term mark with impaired memory, concentration or concentration. Fatigue is very common in the months that follow subarachnoid haemorrhage a it is following other types of stroke.
Emotional lability may be more common including symptoms of depression. Although such symptoms may slowly improve it is not unusual for them to persist for twelve months or more.
Treatment
The severity of the initial haemorrhage is a significant factor in the ultimate outcome. Prompt neurosurgical treatment to stabilise a patient and secure the aneurysm is usually advisable. Occasionally an emergency neurosurgical procedure to divert obstructed CSF or relieve a blood clot from pressing upon the brain.
To learn more about the methods to secure an aneurysm from any further bleeding please see the pages on endovascular and microsurgical treatments.
