Cerebral “berry” aneurysms are sac or balloon like out-pouchings of intracranial arteries, usually occurring at the point at which one artery divides from another. They frequently occur at well-recognised main branching points, but may occur at almost any branch point on the medium and larger cerebral arteries. Approximately 25% occur at the anterior communicating artery, 25% at the division point of the middle cerebral artery, and 25% at the origin of the posterior communicating artery.
Aneurysms are clinically important because they constitute a point of weakness in the cerebral circulation and may leak or rupture, producing a haemorrhage into the brain (intracerebral haemorrhage) or subarachnoid space (subarachnoid haemorrhage).
The mortality and morbidity of these haemorrhages is high, with up to 40% of sufferers either dying or being disabled. There is a high risk of recurrent haemorrhage in survivors, with the same dire prognosis, and, as a result, treatment is primarily directed towards isolating the aneurysm from the circulation, by either microsurgery or intravascular occlusion techniques (commonly referred to as ‘coiling’, because of the use, in many cases, of coils of platinum wire inserted into the aneurysm by a fine intravascular catheter, under x-ray control).
Aneurysms which are discovered before haemorrhage will often be considered for planned elective treatment, by whichever technique is considered to provide the best combination of safety, effectiveness and durability of control.
Factors which may influence this decision include aneurysm location, size and conformation, experience and skill sets of the treating clinicians, patient age, and patient preference.
In certain circumstances, it may be judged that the risks associated with treatment outweigh the risks of the natural history of the particular aneurysm. In this situation a conservative course of observation may be recommended.
Fusiform aneurysms are dilatations in segments of intracranial vessels, which are less vulnerable to haemorrhage but may be associated with compressive or thrombotic (clotting) complications.
Arteriovenous Malformations (AVM’s)
AVM’s are congenital abnormalities of the intracerebral circulation, in which the capillary bed that normally lies between the inflowing high pressure arterial side of the circulation and the outflowing low pressure venous side of the circulation, is absent, resulting in direct communication between arteries and veins. This results in the formation of dilated elongated thin-walled vessels, carrying high-pressure blood flow, which drain into dilated venous channels. These lesions may be clinically silent, produce neurological symptoms (seizures, focal neurological deficit), or present as subarachnoid or intracerebral haemorrhage.
The risk of death from a bleed occurring from an AVM is generally less than the risk from a ruptured aneurysm, but the risk of neurological injury is high, and recurrent bleeding is a continuing threat.
Treatment options are dictated by the characteristics of the AVM (size, location, complexity, relationship to vital brain structures), and include microsurgical excision, endovascular occlusion, and focussed irradiation. Sometimes more than one of these techniques may be required to be employed.
Treatment of intracranial vascular abnormalities is based upon precise knowledge of the anatomy of the particular lesion.
A number of investigational techniques are available, including CT scanning, CT angiography, MRI and MRA scanning, digital subtraction angiography, and frequently more than one investigation will be utilized to optimise pre-treatment planning.
The surgeons at Neurosurgery Tasmania have extensive experience in managing complex vascular anomalies of the cerebral circulation, and consult with endovascular physicians to provide the widest range of management options.