Brain AVM’s

What is a Brain AVM?

An arterio-venous malformation (AVM) of the brain is an abnormal communication between brain arteries and veins across a ball of tangled abnormal small vessels (nidus). This results in high-pressure arterial blood flowing rapidly into veins that are not designed to hold that flow and pressure. This can result in bleeding in the brain (a type of stroke) that can cause permanent disability or death. AVMs can also cause seizures and migraine-type headaches.

Whilst there are a variety of treatment options available for brain AVMs, not all AVMs need to be treated (because some have a low risk of bleeding) and some are considered too high risk for treatment. However, with improving endovascular techniques, we are getting better at downsizing large AVMs so that we can then treat them further with embolization, surgery, or radiation.

Diagnosis

MR Angiography

MR angiography (MRA) is useful for detecting AVMs and a special type of MRA with gadolinium dye (time-resolved MRA, also known as MR-TRICKS) can be used to assess AVMs and follow-them up over time. At Sydney Aneurysm, we make extensive use of MR-TRICKS with the help of our colleagues at St Vincent’s Public Hospital Medical Imaging to follow-up AVMs so we can reduce the number of invasive angiograms a patient needs over their lifetime. MRI with vessel-wall imaging can also be used to assess aneurysms that have developed inside AVMs to look for wall instability.

Cerebral Angiography (DSA)

Cerebral angiography is the gold standard for assessing AVMs because it can accurately map the arterial feeders, the nidus, the draining veins, and look for small aneurysms developing inside the AVM that might increase the risk of rupture. Also, it allows us to see what impact the shunting of blood through the AVM is having on the remainder of the brain. Before any treatment for an AVM, a high-quality cerebral angiogram is essential to get the best possible picture of the structure of the malformation.

Treatment Options

  • Embolization
  • Open Neurosurgery
  • Stereotactic Radiosurgery

Embolization involves blocking vessels that supply or drain the AVM by going through the arteries and veins (usually from thigh or wrist access) – endovascular treatment. We use a lava-like liquid to block off the blood supply to the AVM in stages so we can reduce its size, and then potentially cure the AVM by blocking the nidus at the last procedure. Alternatively, if we have downsized a large AVM with embolization, they may now be candidates for open surgery or radiotherapy.

Embolization has been underutilized in Australia for many years because many patients were treated by open surgery. Dr Bhatia trained with world leading experts in the embolization of AVMs (Professor Timo Krings and Professor Vitor Mendes Pereira) and can provide you with expert advice and embolization treatment if appropriate.

Make sure your surgeon or INR practitioner discusses the option of embolization with you and make sure you have your embolization performed by someone with high-level international training in this complex and delicate procedure.

Open surgery (microsurgery) is a well described method of treating small to moderate size AVMs and can be very effective in the appropriate locations in the brain. If Dr Bhatia believes you would benefit from open surgery, he will refer you to a neurosurgeon with expertise in the procedure. Additionally, if you are considering surgery but have been told by a surgeon that your AVM is too large, we can discuss with you the option of embolizing part of the AVM to reduce its size to make it easier for the surgeons to remove.

Stereotactic radiosurgery is an effective and well tested treatment option for small to moderate sized AVMs, particularly if they have never bled before. It involves very targeted radiotherapy aimed at the nidus of the AVM – supervised by a neurosurgeon. The treatment takes up to three years to be effective, which is why the treatment is more useful for patients who have never had a bleed before. Ruptured AVMs often need to be cured earlier than that if possible, to prevent rebleeding.

At Sydney Aneurysm, we can perform embolization to downsize an AVM so that it is more suitable for radiosurgery. If we feel you would benefit from radiosurgery, Dr Bhatia will refer you to a colleague with extensive experience in the procedure.

FAQ’s

Very unlikely. Whilst we used to believe people were born with AVMs, we now know that they develop most often between late childhood and early adulthood, usually when the blood vessels of the brain are remodelling and replacing their normal cells at a higher rate. A small number of patients may have a genetic predisposition to developing brain AVM’s (e.g. Hereditary Haemorrhagic Telangiectasia, CM-AVM). However, most patients have no family history of AVMs and they develop spontaneously.

 

We now know that most brain AVMs have a localized mutation in a gene called K-RAS, that has developed just in the blood vessels of the AVM but not the rest of the body (somatic mosaic mutation). These localized mutations are not passed on to our children.

Click on the links below for Brain AVM Resources