A cerebral (brain) aneurysm is a bulging or ballooning out of a part of a blood vessel wall due to a weak point in the latter’s wall. As the aneurysm grows, the vessel wall becomes thinner and weaker. It can become so thin that it spontaneously leaks or ruptures, releasing blood into the space around the brain called the subarachnoid space. This results in a subarachnoid haemorrhage (SAH). Blood can also leak into the cerebrospinal fluid (brain fluid) or into the brain substance itself, resulting in an intracerebral haematoma (blood clot). This blood can irritate, damage or destroy nearby brain cells. In more serious cases, the bleeding may cause brain damage, paralysis, coma or even death.
Most people with brain aneurysms do not experience any symptoms prior to the onset of the rupture. The rupture occurs suddenly. Up to 40% of the people experience ‘sentinel headaches’ days to weeks before the rupture and these are thought to be ‘warning leak symptoms’. At the time of aneurysm rupture, the following may occur:
(Any of these symptoms are very serious, and emergency medical attention should be sought immediately.)
To lessen the risk of rupture and prevent development of brain aneurysm, avoid consuming any substance or doing any activity that may lead to a sudden increase in blood pressure – for example, smoking, intake of caffeine or stimulant drugs or straining exercise (e.g. weight lifting).
Who is affected?
Aneurysms can occur in all age groups, with the peak age of presentation of a ruptured aneurysm between 50-60 years. Women have a higher incidence of this occurrence than men.
The exact mechanisms by which aneurysms develop are still not fully understood. Previously thought to be congenital defects in the vessel wall, there is little evidence for such inherited weakness. It is now thought to be a degenerative condition with a number of contributory factors.
How is a ruptured cerebral aneurysm diagnosed?
Computerised Tomography (CT) Scan
When an aneurysm ruptures, bleeding usually occurs in the subarachnoid space of the brain resulting in a subarachnoid haemorrhage (SAH). This is best diagnosed with a CT scan of the brain. This can be performed in minutes and is the investigation of choice. The location of subarachnoid blood on a CT scan can provide useful information on the location of an aneurysm and the neurological deficits caused.
Cerebral angiography is a special x-ray procedure that provides a series of pictures of the blood vessels in the head and neck. Cerebral angiography identifies the size, configuration and exact location of an aneurysm. This procedure is performed before surgery, and often a few days after surgery, to evaluate the placement of an aneurysm clip. Cerebral angiography involves inserting a small flexible tube, called a catheter, into an artery, usually in the groin. The catheter is moved through the artery to the large blood vessels just above the heart. After the catheter is in place, a dye is injected and this is carried in the blood to the arteries in the brain. A number of x-ray pictures are then taken, thereby outlining or mapping the arteries in the brain.
Computed Tomography Angiography (CTA)This is a non-invasive method, utilising CT technology, of outlining the arteries in the brain. While the gold-standard of looking for an aneurysm remains cerebral angiography, CTA is gaining popularity today.
Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA)
MRI is a computerised method of viewing the brain in three-dimensions by using a strong magnetic field instead of x-rays to obtain the pictures. MRI produces more detailed images of the brain and soft tissues than CT regular x-rays. This investigation is sometimes used to supplement a CT scan.
MRA is another non-invasive investigation, utilising MR technology, to map out the arteries in the brain. With a good quality MRI machine, a high resolution of these arteries can be obtained. MRI’s however, take a longer time to perform compared to a CT scan.
In the management of a patient with a ruptured aneurysm, the immediate goal is to prevent a second bleed as re-bleeding has a 60-80% risk of death and severe disability. The risk of a re-bleed is approximately 1.5% per day, reaching a cumulative risk of 20% at the end of the first 2 weeks, and 50-60% at the end of 6 months.
The best treatment option is often individualised, depending on the site, shape and location of the aneurysm. The patient’s age and clinical condition are also factors to consider.
Surgical Therapy or Clipping
Surgical clipping of a brain aneurysm is performed by a neurosurgeon. Access through the skull is obtained via a craniotomy (opening through the skull, often with a special drill / saw). With the use of a microscope, the neurosurgeon then carefully traces the blood vessel involved to look for the ruptured aneurysm. One or more metal clips (usually made from titanium) are then placed across the base, or neck, of the aneurysm. This secures the aneurysm, preventing blood from entering the aneurysm which would otherwise cause a re-rupture. Angiography is commonly performed after the surgery to visualise the closure of the aneurysm and preserve normal flow of blood in the brain.
Endovascular Therapy or "Coiling"
Endovascular coiling is a less invasive procedure which is performed by an endovascular surgeon. A catheter is threaded through an artery in the groin and carefully advanced into the brain. By releasing small coils into the aneurysm from within, the latter is packed such that blood can no longer flow into the aneurysm, preventing a re-rupture.
It is important to understand that surgical clipping or endovascular coiling secures the aneurysm to prevent a second bleed. The damage caused by the original bleed is still not overcome. Treatment of the patient continues medically, to help him recover any possible on-going damage and to prevent further complications that arise. This often entails intensive care management.
What are the complications of a subarachnoid haemorrhage?
The complications or ill-effects of a subarachnoid haemorrhage include:
When blood leaks out during an aneurysm rupture, it comes into contact with normal blood vessels. This may irritate the blood vessels, which then go into vasospasm (constriction leading to a narrow lumen). When severe, insufficient blood flows to portions of the brain resulting in a further stroke and even death. Cerebral vasospasm peaks at about 7-10 days after rupture of the aneurysm and can last as long as 2 to 3 weeks. It can be monitored by a combination of careful neurological examination and Transcranial Doppler ultrasound. When clinically apparent, an angiogram is performed. Injection of a drug called Nimodipine, directly into the lumen of the affected arteries during this procedure can relieve vasospasm.
To prevent vasospasm, Nimodipine is given to the patient for a duration of 21 days. Post-operatively, the patient’s blood pressure is often kept a little high and his blood diluted a little to counter possible vasospasm.
Blood from a ruptured aneurysm can block the circulation of cerebrospinal fluid (brain fluid), causing a build up of this brain fluid within the ventricles (fluid-containing cavities) of the brain – a condition called hydrocephalus. Pressure in the brain subsequently rises and death can ensue if left untreated. To stop this brain fluid from building up, a temporary drain or a permanent shunt may be placed into the ventricles.
Other possible complications include brain swelling, seizures, cerebral salt wasting, syndrome of inappropriate ADH secretion (SIADH), neurogenic pulmonary oedema (fluid in the lungs) and cardiac (heart) abnormalities.
What is the recovery process?
The recovery process following a ruptured aneurysm is different with every patient. It often depends on the amount of damage in the initial rupture. If the patient has severe damage from the beginning, prognosis is often guarded. On the other hand, if the initial damage is limited and the aneurysm is successfully secured, the chance of a good recovery is much higher. The recovery process, however, may take many months to a year or more. A younger and fitter individual will have a better chance of a good recovery as compared to an elderly and weaker individual.
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