Trans-venous Endovascular Treatment for Cerebral AVM (Arterio Venous Malformation)

Normally, a fine network of microscopic capillaries connects arteries and veins in all tissues, including the brain. Capillaries assist in slowing down blood flow between arteries and veins. An AVM is a tangle of feeding arteries and draining veins that have abnormal connections, bypassing capillaries. The high-pressure blood flowing from arteries directly into thinner walled veins gives them a high risk of haemorrhage or bleeding. This abnormal blood flow is called a shunt. AVMs vary between a few millimetres to several centimetres in size and can occur anywhere in the brain or spinal cord. For more information about AVMs, please see our procedural leaflet ‘Cerebral AVM (Arterio-Venous Malformation) Endovascular Treatment: Information for patients’ available within the department or on our website.

Trans-venous approached embolisations can also be performed on other vascular lesions like dAVFs (dural Arterial Venous Fistula), please see our leaflet for ‘Cerebral DAVF (Dural Arterio-Venous Fistula) Endovascular Treatment: Information for patients’ available within the department or on our website.

You may have been referred for trans-venous endovascular treatment as you have previously suffered an intracranial haemorrhage, or have experienced common symptoms such as seizures, headaches, or neurological deficit. Some patients have asymptomatic lesions that have been identified on imaging or investigations as ‘incidental findings.’

A trans-venous approach refers to a technique in which the Interventional Neuroradiologist (INR) will insert a catheter into a vein at the top of your leg or neck and feed this up into a position close to the AVM. Once in place, this can be used to enable embolisation or balloon occlusion of your AVM.

This approach is sometimes more effective in reaching the AVM and allowing effective embolisation. A variety of embolic agents can be used depending on your pathology. These include:

• Embolic liquid – most commonly a material called ‘Onyx’
• Embolic coils
• Remodelling balloons

Endo-vascular treatments or embolisations are carried out to protect the AVM from bleeding. In an embolisation, special glue-like liquid or other materials as described above, are injected into the malformation in order to cut off the blood supply.

An embolisation is normally performed to treat the AVM completely. If the malformation is particularly large or complex, an embolisation may be completed prior to further surgical excision (removal) or gamma knife treatment of the lesion, in order to reduce blood flow and ensure further treatment is safer.

All treatments and procedures have risks, and we will talk to you about the risks of having an AVM embolisation. No two AVMs are the same: The risks of embolisation vary from one AVM to the next according to the size, position, and configuration of the vessels. Sometimes it is not possible to embolise an AVM safely. Trans-venous approached embolisations carry similar risk occurrence rates to the trans-arterial approach technique. Your own specific risks will be estimated and discussed with you before the procedure.

The procedure will need to take place under a general anaesthetic; the anaesthetist will discuss the risks of general anaesthesia with you.

Problems that may happen straightaway

During a trans-venous embolisation, a contrast agent will be injected into your veins and arteries. This allows the Interventional Neuroradiologist (INR) to see the blood vessels when an X-ray is taken. Contrast agents are considered safe drugs. However, as with all drugs, they have the potential to cause an allergic reaction. The department and team are well equipped to deal with reactions in the rare event of this happening.

Problems that may happen later

The contrast agent used during a trans-venous embolization is iodine-based contrast which is excreted through the kidneys This may affect kidney function. You will therefore have a blood test to test your kidney function beforehand to ensure it is safe for you to have contrast. The risk of you having contrast will be weighed against the benefit of having this treatment and is decided by the team referring you for an embolisation. For further information on the use of iodine-based contrast agents please see the information leaflet ‘Contrast Agents for X-ray, Fluoroscopy, CT and Angiography Examinations: An Information Guide’ or alternatively visit the trust website.

Problems that are rare, but serious

Trans-venous embolisations are difficult and complex procedures - serious complications are unlikely but are always present. Like all procedures involving the blood vessels of the brain, a trans-venous embolisation carries a risk of stroke which results from either a blockage of a blood vessel or from a haemorrhage. This can range from a minor problem which improves over time to a severe disability involving movement, balance, speech, or vision, or may even be a threat to life. The percentage level of this risk can only really be discussed on a case-by-case basis and depends on the size, position, and configuration of the malformation itself.

Other Problems that occur

Usually, manual compression for a period is placed over the vein puncture after the tube has been removed. This is done to seal the access site. Occasionally a stitch will also be placed over the puncture site. Often there is bruising and sometimes bleeding. It is rarely serious but can go on for a few hours. Very occasionally, there is damage to the blood vessel requiring a further surgical procedure.

Any problem is usually apparent during or immediately after the procedure, or during the next few days whilst you are still in the hospital.

Radiation Risk

The use of X-rays during any procedure results in a very small increase in the risk of developing cancer in the future. For the more complex cases, temporary hair loss and skin erythema (reddening) may occur a few weeks after the procedure. Our state-of-the-art imaging equipment and modern techniques help to ensure the radiation dose is as low as possible. In addition, your doctor will have made a judgement about your risk and benefit before agreeing to the procedure, including the risk to your health of not having the procedure.

Female patients of childbearing capacity between the ages of 12 and 55 years are required by law to be asked about possible pregnancy when undergoing examinations involving x-rays of the abdominal area. Patients who either are or think they may be pregnant must inform the Neuroradiology Department as soon as possible. In some urgent cases the procedure may still go ahead but with additional precautions in place. To reduce the risk for early and unknown pregnancies, transvenous embolisations are usually performed within the first ten days of the menstrual cycle when pregnancy is much less likely.

The Interventional Neuroradiologist performing the procedure will discuss all possible risks with you and give you the opportunity to ask questions.

If we think you will benefit from embolisation of your AVM we will offer you this procedure, but the final decision whether or not to have this procedure is entirely yours. To decline the procedure will not affect your personal care. However, it may mean that your doctor cannot be as certain or specific about any future treatment or procedures and it may affect some clinical decision making.

Certain patients with multiple risk factors or who have very complex malformations for which treatments would be considered high risk, may have conservative management of their malformation instead. This would involve interval imaging and clinical assessment to monitor the progression of the lesion. However, this would not reduce the risk of bleeding. Some patients may be able to take medication to reduce symptoms they experience.

Gamma Knife Treatment

This involves a high dose of radiation directed specifically at the nidus or nest of tangles of an AVM. This causes the malformation to shrink over time, which usually takes about 3-4 years to fully cure. This can vary between patients and the size of the lesion. Gamma knife tends to be selected for treatment of smaller AVMs.

Surgical excision

This involves a craniotomy or creating an opening in the skull to allow the neurosurgeon to surgically remove the vessels. The feeding arteries and draining veins that remain in the brain are then clipped off. Surgery is a well-established and effective treatment and can provide immediate protection from rupture or haemorrhage. This might not be an option for AVMs deep within the brain.

Other endovascular techniques

Some patients will have a ‘trans-arterial approached’ embolisation, meaning the main catheter is placed into the feeding artery and the AVM is accessed and embolised from the arterial side. Trans-arterial approached embolisations carry similar risk occurrence rates to the trans-venous approach described above. Sometimes a combined trans-arterial and trans-venous approach will be selected. Your own specific risks will be estimated and discussed with you before the procedure. As with trans-arterial embolisations, all alternatives carry their own specific risks, and your Neurosurgeon will discuss these in detail with you. If you are unsure about the treatment, you are due to receive do not hesitate to speak with your referring doctor.

You will be asked to arrive at the hospital the day before or on the morning of your procedure. If you are arriving the morning of your procedure, you will be asked to arrive at 8am to the surgical reception unit (SRU) or to the ward specified by the admission officer in contact with you. Your procedure may take place at any time during the day due to emergency cases, but we will endeavour to keep you informed and perform your procedure as early in the day as possible.

The procedure is performed by specialist doctors called Interventional Neuroradiologists (INR). The INR will see you on the ward to explain the procedure and any associated risks. Please feel free to ask any questions at this time.

The procedure is performed under a general anaesthetic this means you will be unconscious or 'asleep' throughout. Your anaesthetist will talk to you about the anaesthetic, and what you can expect when having a general anaesthetic both in clinic before the procedure and again briefly on the ward the day of your procedure. You will need to fast for six hours before your procedure. Your anaesthetist will confirm with you a specific time you must stop eating and drinking. You should still take all of your normal medications at the normal times throughout this period with a sip of water, unless advised otherwise.

You will be asked to change into a hospital gown and disposable underwear. A member of staff, usually the nurse caring for you, will accompany you to the Neuroradiology department.

It is important that you are involved in all the decisions about your care and treatment. If you decide to go ahead with treatment, by law we must ask for your consent and will ask you to sign a consent form. This confirms that you agree to have the procedure and understand what it involves. Staff will explain all the risks, benefits, and alternatives before they ask you to sign a consent form. If you are unsure about any aspect of your proposed treatment, please don’t hesitate to speak with a senior member of staff.

The trans-venous embolisation is performed while you are under general anaesthetic. The anaesthetic team will put you to sleep in the anaesthetic room prior to transfer to the angiography suite.

The procedure is performed by the INR in the angiography suite (a type of operating theatre) located in the Neuroradiology department. It usually takes between one and three hours. A dedicated team of radiologists, radiographers, anaesthetists, and nurses will be in the angiography suite to monitor you closely throughout the procedure.

Once the procedure has commenced, the INR will place a thin, flexible, plastic tube (catheter) into the vein normally in the groin. The catheter passes through the main veins in the body called the vena cava and finally into the veins in your brain. Before the embolisation begins the INR will inject the cerebral veins to confirm the best approach. A contrast agent will be injected which will allow the blood vessels to be seen when an X-ray is taken.

Depending on the configuration of the malformation and its associated blood vessels, other techniques may be used. Normally two catheters are used to access both the feeding artery and the draining vein. The INR will place another catheter into the femoral artery, in the opposite groin or side, which passes through the main artery in the body called the aorta and into the cerebral arteries.

When an accessible feeding vein is identified, the catheter is placed into this feeding vein. Following this, a second microcatheter is inserted inside the first. Embolic agents can then be used to seal off and obliterate the malformation. Occasionally small metal coils or permanent balloons will be used too. This embolic material creates a blockage to stop blood flowing into affected vessels.

Further x-rays will be taken to ensure the malformation has been obliterated as much possible. Once the INR is satisfied with the result, the catheters are removed and the blood vessel in the groin or arm is sealed with a stitch.

After the procedure, you will spend some time in the recovery unit or high dependency unit (HDU) before being transferred back to your ward. These units provide a high level of monitoring. You will be on bed rest for at least a few hours following the procedure to ensure the entry site of the catheter in your groin or arm has begun to heal and that you are neurologically stable.

You can expect to remain in hospital for a minimum of four to five days after the procedure, until you are walking around and feeling back to normal. You should plan to take some time off work, at least a week or two, and you should arrange to have someone to stay with when you first return home. Everyone is different and people recover from these procedures at different rates.

It is common to experience headaches in the days or weeks following the procedure. You will be given pain killing drugs to help.

You may also experience some pain or bruising at your groin, where the catheter was placed, this should reduce over a few days.

For any non-urgent questions or concerns you may have following your procedure, please contact the Neurovascular Clinical Nurse Specialists.

• The Brain & Spine Foundation UK
  Telephone: 0808 808 1000

UCLH cannot accept responsibility for information provided by other organisations.

• Brain& spine foundation. 2017. Vascular malformations of the brain. [Online]. [20 April 2020]. Available from: https://www.brainandspine.org.uk/our-publications/booklets/vascular-malformations-of-the-brain/
• NHS Commissioning Board. 2013. Clinical Commissioning Policy: Stereotactic Radiosurgery for Cerebral Arteriovenous Malformations. [Online]. [20 April 2020]. Available from: https://www.england.nhs.uk/commissioning/wp-content/uploads/sites/12/2013/10/d05-p-c.pdf
• Department of Neurosurgery. 2014. Arteriovenous Malformation (AVM). [Online]. [20 April 2020]. Available from: http://www.neurosurgery.wustl.edu/patient-care/specialties/aneurysm-cerebrovascular/arteriovenous-malformation-avm-171

Lysholm Department of Neuroradiology

National Hospital of Neurology and Neurosurgery, Queen Square, London, WC1N 3BG

Email: uclh.referrals.neurorad@nhs.net

Direct line: 020 344 83444

Switchboard: 0845 155 5000

Extension: 83444/ 83446

Fax: 020 344 84723

Website: www.uclh.nhs.uk/nhnn

Neurovascular Clinical Nurse Specialists

National Hospital for Neurology and Neurosurgery, Queen Square, London, WC1N 3BG

Direct line: 020 344 83523

Switchboard: 0845 155 5000

Extension: 83523

Email: uclh.neurovascularnurse@nhs.net

Website: www.uclh.nhs.uk/nhnn

The Lysholm Department of Neuroradiology reception is located in Chandler wing, on the lower ground floor of the National Hospital for Neurology & Neurosurgery, Queen Square.

Please turn left when you exit the chandler wing lifts on the lower ground floor to find our main departmental reception.