Intracranial Aneurysms

An aneurysm is an abnormal dilatation of a blood vessel, usually an artery, due to a weakness in its wall. Intracranial aneurysms are most commonly saccular, and have the appearance of a discrete bulge on the side of an artery. Because of their shape they are also often called “Berry” aneurysms. These arteries carry high-pressure blood to the brain, and the aneurysms usually occur where the arteries are branching under the brain.
 
Intracranial aneurysms are very rare in childhood, and usually occur in adults, presenting with increasing frequency with advancing age. They occur slightly more commonly in females than males. Although some families have a high incidence of aneurysms, most occur sporadically and it is not generally considered to be an inherited condition. Most people who develop aneurysms are otherwise fit and healthy, although some rare connective tissue, kidney and blood vessel diseases are associated with an increased risk of developing aneurysms. Smoking and high blood pressure are also thought to increase the risk of aneurysm formation.

Yes, I want to join the fight against aneurysms and

Make a donation

 

 


 Aneurysms usually cause no symptoms at all until they rupture. Although the diagnosis of an aneurysm is occasionally made coincidentally in people who have scans for other reasons (eg after head injury, etc), most people with aneurysms are totally unaware of their presence, often for many years. There is currently some controversy regarding the risk of such an asymptomatic aneurysm rupturing, although we generally believe that it is probably less than 1% per year in most cases. Therefore, people with coincidental aneurysms are strongly advised that they do have time to seek specialist advice from a neurosurgeon who specialised in aneurysm treatment (cerebrovascular neurosurgeon), and to consider the treatment options.

However, most aneurysms only become apparent when they do actually rupture, and this is a neurosurgical emergency. Aneurysm rupture causes sudden high-pressure bleeding into the fluid (CSF) which surrounds the brain and spinal cord. This is called subarachnoid haemorrhage (SAH). SAH typically causes an abrupt onset of headache, often with vomiting and neck stiffness, and not infrequently can cause sudden loss of consciousness and even sudden death. Occasionally the aneurysm can burst directly into the brain (intracerebral haemorrhage), causing paralysis or loss of speech or other symptoms commonly attributed to stroke.

People with these symptoms who attend hospital are usually diagnosed with subarachnoid haemorrhage or intracerebral haemorrhage when an emergency CT scan shows the blood around or in the brain. Occasionally a sample of CSF is also tested to detect the blood. Although the CT scan is excellent at demonstrating the bleeding, it usually does not show the aneurysm itself, and the patient usually needs a specialised blood vessel xray (angiogram) to demonstrate the aneurysm.

At this time the aneurysm has temporarily sealed itself with a fragile clot over the rupture site, and the main concern is that the aneurysm will bleed again. This rebleeding is a devastating complication, with between 40-60% of rebleeding patients in hospital dying. The risk of rebleeding is highest in the first 12-24 hours after the initial SAH, with about 10-17% of SAH patients rebleeding during this time.

Although rest, blood pressure control and pain relief have traditionally been used to reduce the risk of rebleeding, the only effective way to prevent rebleeding is to mechanically secure the aneurysm. This can be done with microsurgery, using the operating microscope to expose the vessels under the brain and applying a clip around the neck of the aneurysm to seal it off from the circulation. Alternatively the aneurysm can be secured by endovascular treatment (that is by passing fine tubes though the blood vessels under xray control into the aneurysm, and then introducing fine platinum coils (or occasionally other devices or substances) into the aneurysm and blocking it off internally. Both treatments are highly specialised and delicate procedures. The choice between microsurgery or endovascular treatment depends primarily on the architecture of the blood vessels and aneurysm, and is ideally made by a cerebrovascular neurosurgeon in consultation with an interventional radiologist.

After the aneurysm has been secured, the patient is still at risk of developing other complications over the next 1-3 weeks. The blood around the brain can irritate the blood vessels causing spasm of arteries, which if untreated can cause stroke. The blood also disrupts the normal flow of CSF around the brain, causing build up of this fluid (hydrocephalus) which can require drainage or shunting. Patients also need to be closely watched for fluid and electrolyte abnormalities, heart rhythm problems, chest infection and blood clots in the legs. Therefore most patients are monitored in a specialised neurosurgical high-dependency unit.

Many patients who survive the initial SAH, particularly those who arrive at hospital with a good conscious state, do make a complete recovery, often being discharged to home within 1-2 weeks. However, some patients have brain injury from either from the initial aneurysm rupture, rebleeding, treatment of the aneurysm, or because of vasospasm. Depending on the extent of the brain injury, these patients’ disabilities may range from relatively minor and transient, to profound and permanent (even causing death in some cases). Patients with disabilities usually benefit from rehabilitation after the acute hospital stay. 

International Familial Aneurysm Research Study

This project, lead by Mr John Laidlaw studies those patients that could be at risk from development of cerebral aneurysms due to a genetic basis.  In the past it has been considered that there was no direct inheritance of the risk to develop cerebral aneurysms, but more recent investigations have shown the possibility of an inherited basis.  This is a large international investigation, which will help study the genetic basis for the development of cerebral aneurysm, through identification of those families with familial aneurysms.

CT Angiography in the Diagnosis and Treatment of Cerebral Aneurysms

Mr Laidlaw is also studying the role of CT angiography, and its possible replacement for conventional angiography in the diagnosis and management of patients with intracranail aneurysms.  This would potentially signficantly reduce the morbidity associated with cerebral angiography  in these very sick patients.