Please remember that this is general information and is meant only as a guide. All diagnoses and treatment options should be discussed in full with a qualified clinician.
An AVM is a collection of abnormal blood vessels. It consists of dilated arteries feeding into a tangled mass of blood vessels and can occur at any site in the body. However, they are of particular concern when they appear in the brain because of the possible serious consequences of haemorrhage.
AVM can present with the following symptoms:
The prevention of haemorrhage is usually the main indication for treatment and this is only achieved with complete obliteration or removal of the AVM. The main treatment methods are outlined below.
Complete excision is a proven effective treatment. The advantage of complete removal is that the benefits are realised immediately. The disadvantage, as with any surgery, is the relatively lengthy recovery time, the risk of general anaesthesia and the risk of post-operative haemorrhage or infection. Also, some deeply-seated lesions are deemed to be inoperable.
Gamma knife has the advantage of being minimally invasive, thereby avoiding operative damage and a lengthy post-operative recovery period. It is most effective on small lesions; commonly a success rate of 80 per cent (or more) is quoted for AVMs under 3 cm in diameter, but this depends on the location of the AVM within the brain. For lesions greater than 3cm, the success rate for complete obliteration decreases.
A disadvantage of gamma knife is that it may damage a small amount of normal brain tissue directly surrounding the lesion. Increasing the dose delivered to the AVM increases the chances of obliteration but also increases the chance of inducing a neurological deficit caused by damaging the normal surrounding tissue. Therefore careful consideration is required when deciding upon dose, especially when the AVM is located in a sensitive part of the brain. Another disadvantage is that obliteration of AVMs following gamma knife treatment can take up to two years. Lengthy follow-up is therefore required, with an MRI scan usually being performed 24 months post treatment and every 6 months thereafter until the AVM is no longer visible. An angiogram is then performed to confirm obliteration.
Embolisation involves injecting liquid glue (or coils) into the feeding vessels of the AVM, and tends to be used for small AVMs. Embolisation alone is unlikely to obliterate larger AVMs completely but it can reduce their size. This technique tends to be used to complement surgery or gamma knife treatment, rather than as a definitive treatment in itself.