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Radiation Treatment of Brain Arteriovenous Malformations (AVM)

 

Why Treat My AVM?


The reason that treatment is offered is to try to prevent bleeding or haemorrhaging from the AVM. Bleeding from a brain AVM may injure the surrounding brain resulting in a stroke-like state, permanent disability or even death. Not all people who have AVMs will bleed during their lifetime. The risk is estimated to be about 4% per year. This means that 4 out of every 100 people with an AVM will have a bleed (haemorrhage) during any one year. The collective risk over one's lifetime may be extremely high especially in a young person. For instance, in a 50 year old with an AVM who has a life expectancy of 30 years, the risk of bleeding in his/her lifetime is about 71%.



 

What is Radiation Treatment?


This treatment is also known as Radiosurgery or Stereotactic Radiosurgery. A narrow x-ray beam is focused on the AVM such that a high dose is concentrated on the AVM with a much lower dose delivered to the rest of the brain. This radiation causes the AVM to close off over a period of 2-3 years in up to 80% of patients. The risk of complications is low. Until the AVM is closed off, the risk of bleeding still persists.



 

How Does it Work?


The radiation delivered to the AVM works by inducing changes in the walls of the blood vessels forming the AVM. As these walls thicken, the vessels gradually close off.

In up to 80% of patients, complete closure results so that no more blood flows through the AVM. The chances of bleeding then is reduced to zero. These changes take place gradually and may take upwards of two to three years to occur.



 

The Procedure


Stereotactic Radiotherapy is a non surgical procedure. Although the actual radiation treatment takes only a few minutes, the planning and preparation requires you to be at the hospital for a full day. Prior to the day of the procedure you will have an appointment at the Sunnybrook Health Sciences Centre for a brain MRI scan.

The Day of the Procedure

Stage 1

On the morning of the procedure you will go to the Toronto Sunnybrook Regional Cancer Centre. 
To pinpoint your AVM accurately, your doctors need you to undergo x-rays while wearing a special headframe. The headframe is applied by a doctor using a local anaesthetic. Though bulky, the headframe is lightweight. Special plates are inserted into the headframe at the time of the x-rays. These have special markings that allow your doctors to calculate the exact position of your AVM. The precision is needed to focus the radiation on the AVM while delivering a much lower dose to the rest of the brain. A CT scan of the brain done with intravenous contrast will be performed shortly after application of the headframe.

Stage 2

Wearing the headframe, you will go over to the radiology department at the Sunnybrook Health Sciences Centre for a cerebral angiogram. This is similar to your previous angiograms. Dye is injected through groin vessels into the AVM and x-ray pictures of your AVM are taken. This procedure lasts less than an hour.

Stage 3

The information from your x-rays is then used by a team consisting of a radiation oncologist, neurosurgeons and medical physicists to plan your treatment using a computer.

Stage 4

The final stage is the actual treatment itself. The linear accelerator (LINAC) is prepared for your treatment. A team consisting of doctors, physicists, radiation therapists and nurses work together to position you accurately on the treatment table. During the five or seven minutes it takes to deliver the radiation, you will be monitored by a closed circuit TV camera. You will feel the x-ray table slowly moving through an arc and hear the machine move along with you. Nothing will actually touch you and you will not feel the radiation.

After Treatment

Immediately following treatment, the headframe is removed. A bulky bandage is applied to your head to apply pressure to the points where the frame was applied to your head. The bandage can be removed after 24 hours.



 

What are the Side Effects?


Very few patients experience headaches, nausea or seizures shortly after treatment. Hair loss is also rare occurring months after radiation and only in those patients whose AVM lies just underneath the skull bone. Such hair loss is usually temporary and usually covers an area the size of a quarter.

Approximately 3-5% of patients develop long term complications following radiation. These usually take months to years to develop. The symptoms that occur depend upon the location of the AVM and the functions of the brain immediately surrounding the AVM. If the AVM is in an area of the brain controlling the arm or leg, then stroke-like problems like weakness and numbness in an arm or leg may occur. Your doctor will discuss the specific details of your AVM and such side effects with you.



 

What are the Advantages of Radiation Treatment?


  • Not an operation.

  • The AVM will close off in up to 80% of patients 2 to 3 years after treatment.



 

What are the Disadvantages?


  • This form of treatment can only be done for smaller AVMs.

  • Long term side effects occur in about 3-5% of patients as a result of the treatment.

  • There is still a 4% chance of bleeding every year until the AVM is completely closed off.



 

Bleeding After Radiation Treatment


It is important for you to know that the effects of radiation are slow and it usually takes upwards of two years for an AVM treated with radiotherapy to be closed.  During this period, a person may still bleed from the AVM. In other words the radiation treatment does not protect you from bleeding until your AVM has been completely eliminated.