The term ‘AVM’ can be applied to arteriovenous malformations anywhere in the body, but most commonly refers to the abnormalities found in the brain.
AVMs are said to be present where there is an abnormal connection between arteries and veins – allowing arterial blood to flow directly into the venous system without passing through capillaries.
In this article, we consider the most clinically significant type of AVM – cerebral AVMs.
What are AVMs?
- They are messy, tangled groups of blood vessels, where arteries flow directly into veins
- They most commonly occur at the junction of the cerebral arteries, and this can be in the frontal, temporal and occipital lobes, as well as at the cerebellum, but they can affect any part of the brain, including the brainstem.
- They can cause problems by:
- Haemorrhage
- Compression of brain tissue
- Either of which can cause ischaemia or EPILEPSY
- The risks are much lower than in aneurysm
Investigations
- May be seen incidentally (e.g. on MRI / CT)
- Arteriography and non-contrast CT can detect AVM’s > 1cm in size, but arteriography is the investigation of choice and can determine if the AVM is operable or not
- Should be specifically sought, after intracerebral haemorrhage in the non-hypertensive under 50’s.
- Cranial bruits are rare, but suggest AVM
Treatment
- If asymptomatic, they will probably not be treated
- If presenting with epilepsy, then the epilepsy may be treated symptomatically (regular epilepsy treatments)
- Radiotherapy
- This is suitable for AVMs <3cm in size. A proton beam can be used to cause coagulation, which then effectively blocks off the AVM, or more conventional radiotherapy can also be used
- Surgery – May be useful for superficial larger lesions