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Gamma Knife : arteriovenous malformation (avm)

Procedure description

Gamma Knife is a procedure which has been in use since 1968, when Dr. Lars Leksell, a Swedish neurosurgeon, introduced the device in Stockholm, Sweden.  The device is known for its  low complication rate  because of its accuracy and precision.  The device focuses 201 gamma rays, emitted from Cobalt, into a focal point at the center of the sphere.  While the center (where the target is) gets an enormous amount of delivered radiation, any other portion of the sphere (brain) gets a minimal dose.

The Gamma Knife procedure requires a team approach, with a neurosurgeon, radiation oncologist, physicist, radiologist, nurse, and radiation therapist being involved intimately with the care.  The procedure is relatively painless, with the only mild discomfort occurring  during the initial frame placement.  The remainder of the day of treatment is just "boring."  There is no shaving of the head required, and the patient can resume most normal activities the next day.  There have been over 160,000 treatments of Gamma Knife performed world wide.

On the day of Gamma Knife treatment, the patient is taken to the Gamma Knife area, and a Leksell frame (a titanium alloy frame) is placed on the patient's head.  Four pins are affixed to the scalp and skull.  The patient is sedated, and local numbing medicine is used during the frame placement.  Often patients will not even remember this part of the procedure.  Next, the patient is taken to the MRI or CT scanner, where detailed images of the brain are taken.  The images are transported by computer to the Gamma Knife planning station, where the neurosurgeon, radiation oncologist, and physicist will outline the area to be treated, and formulate a dose plan.  All three will agree upon the final treatment plan before treating.  Next, the patient will be taken to the Gamma Knife room, and treatment will commence.  The treatment is painless.  Depending upon the size and shape of the lesion being treated, a number of different positions ("shots") will be used.    After completing the treatment, the frame will be removed, and the patient discharged home. 

When Gamma Knife is used for the treatment of arteriovenous malformations, the likelihood of obliterating the AVM is on the order of 80%.   The arteriovenous malformation may take up to two years to disappear.  If this does not occur, the malformation is still at risk for hemorrhage. 

Procedure Risks

Risks for Gamma Knife for tumor can be broken down into two categories, 1) those related to the operative site of the tumor, and 2) those related to the risks of anesthesia. 

Risks related to the operative site

Avm  site:  The patient has a frame placed on the head.  There are potential risks associated with this, although they are very small.  There may be bleeding or infection associated with the pin placement, and a pin could potentially pierce the skull causing damage to the underlying brain, although these risks are very small. 

Brain injury:  Risks mainly relate to the location of the avm, and radiation to the surrounding brain tissue.  There could be swelling of the surrounding brain.  There could be concomitant seizures, paralysis, stroke, coma and death.  The likelihood of these is very small.  There may be radiation necrosis (dead brain tissue and swelling) associated with the treatment, requiring open surgery to remove.  There is the risk of persistence of the avm, requiring either additional surgery or gamma knife.   Open surgery may be needed for persistent avm, and the open surgical removal may be more difficult as a result of scarring.  If the avm is located close to the optic nerves (nerves to the eyes), there is a risk of blindness, although the Gamma Knife team will do everything possible to minimize these risks.  In addition, there is the theoretical risk of the radiation exposure causing another tumor within the brain or elsewhere in the body.

General Risks:  As a result of the sedatives and local anesthetics used during the procedure, patients may potentially experience cardiac or lung difficulties, although the likelihood is extremely low.  There is also the risk of difficulty with the angiogram used during the procedure, to localize the avm.  There could be a reaction to the intravenous contrast dye, and there could be bleeding from the angiogram site in the leg.  The angiogram could cause a stroke by pushing an embolus into the brain, or the arteries in or feeding the brain could become injured. 

Risks of Anesthesia
Blood clots in the legs, heart attacks, reaction to the anesthetic (local anesthetic and IV sedation used during frame placement).

Post-operative care:

There is relatively little pain associated with Gamma Knife.  Your surgeon will prescribe pain medications for any pain associated with the pin sites, although this will most likely be minimal. 

  1. Follow up appointment will be scheduled with your neurosurgeon and radiation oncologist.
  2. Take it easy the remainder of the day.  You may be tired from a strenuous day.
  3. You may resume activity the following day.  You may take the day off from work, but could most likely return to work, if you have been working, two days after the treatment.
  4. Keep the pinsites clean, and covered with an antibiotic ointment until healed,  This will take several days.
  5. You may shower after you go home.  Keep the pinsites dry and clean.  
  6. Sexual activities are permitted.
  7. If you notice swelling, redness or opening of the pinsites, or if there is any clear fluid draining from it, please contact your surgeon immediately!  If you develop a fever, stiff neck or chills, contact the office immediately.  Take your temperature at 4:00 PM daily until the clips are removed.  Call if greater than 101 degrees Fahrenheit.
  8. If you have a seizure, notify our office or come to the emergency room.
  9. If you develop any new weakness, notify our office.
  10. If you have any questions, call our office, and for after hours emergencies, call the medical society.
  11. Take your medications prescribed on discharge from the Gamma Knife department, as directed.  Your Gamma Knife team will determine whether steroids or other medications are needed.
  12. Make sure to follow up with any other physicians involved in your care.  These may include your family physician, neurologist, radiation oncologist and oncologist.

 

 

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