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A vascular malformation is an abnormal collection of blood vessels with direct blood flow from the arterial system to the venous system. There is a lack of the normal interposed capillary vessels. This renders the vessels fragile and at risk of bleeding or forming aneurysms.
AVMs are present from birth making them congenital lesions. There are numerous theories as to their cause and timing of development but nothing has been confirmed. The majority of AVMs are discovered in people aged 20-40 however they are also the most common cause of subarachnoid haemorrhage in the paediatric population.
AVMs may be discovered incidentally on a routine CT or MRI of the brain for another reason. They most commonly present following haemorrhage which may be intra-cerebral, subarachnoid, intraventricular or a combination of all. Other presentations include mass effect, ischaemic symptoms from steal phenomenon, audible bruits and raised intra-cranial pressure. The symptoms related to these are dependent on the site of the AVM and include:
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