Gamma Knife Radiosurgery


What is Gamma Knife® radiosurgery?

Gamma Knife® radiosurgery, also known as stereotactic radiosurgery, is a form of radiation used to treat brain disorders. Despite its name, this procedure does not involve a surgical incision into the brain. Also, the “blades” of the gamma “knife” are actually beams of highly focused gamma ray radiation. Up to 192 beams of radiation are precisely focused on the lesion/targeted area in the brain. Because the beams are so highly focused, there is little damage to the surrounding healthy tissue.

Compared with traditional surgery, Gamma Knife® radiosurgery does not require general anesthesia. It also avoids other risks and complications of surgery (such as bleeding and infection). There is also little or no post-treatment discomfort or pain. Gamma Knife® radiosurgery is usually performed as an outpatient procedure. Sometimes, however, patients may stay in the hospital overnight. Most patients can resume their usual activities in a day or two. Physical therapy or other rehabilitation is not needed.

What conditions does Gamma Knife® radiosurgery treat?

Gamma Knife® radiosurgery can treat several brain disorders, including:

  • Acoustic neuroma – a non-cancerous tumor that develops around the balance and hearing nerves that connect the inner ear with the brain
  • Arteriovenous malformations (AVMs) – abnormal, snarled tangles of blood vessels
  • Brain tumors (both cancer and non-cancer) – including pituitary adenomas, pinealomas, craniopharyngiomas, meningiomas, chordomas, chondrosarcomas, metastases, and glial tumors
  • Tremors due to essential tremor or Parkinson’s disease
  • Trigeminal neuralgia – an ongoing condition that affects a certain nerve in the face, causing extreme pain
  • Some types of epilepsy

The Gamma Knife® can be helpful in patients with brain lesions that cannot be reached by traditional surgery techniques and in those who are unable to undergo surgery due to their condition or age. It can also be combined with traditional surgery to prevent tumor regrowth. Because Gamma Knife® results occur slowly over time, this is not a procedure for conditions that need immediate treatment.

Procedure Details

What happens before the Gamma Knife procedure?

  • The physician will gather your medical history and perform a complete physical exam. You may undergo additional tests.
  • Tell your physician if you have any of the following: heart pacemaker, aneurysm (brain) clip, implanted medication pump, implanted nerve stimulator, metal implants, metal from trauma, cochlear implant, spine stabilization hardware, severe lung disease, esophageal reflux, are unable to lay flat on your back for 30 to 60 minute periods, or are claustrophobic.
  • Tell your physician if you are sensitive to or are allergic to any medications, latex, tape, contrast dyes, iodine, or general or local anesthetic agents.
  • A family member or friend will need to go with you on the day of the procedure and drive you home after treatment. A Gamma Knife Center nurse will call you the day before your procedure to confirm your arrival time and answer any remaining questions.
  • Do not eat or drink anything after midnight the evening before your procedure.
  • Wash your scalp the night before your Gamma Knife® Wear your hair loose, avoiding the use of clips, pins or bands. Do not use hair spray or other styling products. Your head will not be shaved.
  • Take your morning medications with sips of water the morning of your treatment. Bring all prescribed and over-the-counter medications, including inhalers, with you.
  • On the day of the procedure, wear slip-on shoes; comfortable pants, slacks, or shorts; and a button-up or zip-front shirt with loose-fitting or short sleeves. Do not wear a shirt that must be put on/taken off over your head.

How is Gamma Knife® radiosurgery performed?

Gamma Knife® treatment involves several steps.

  1. First, an IV line is inserted into your arm. This provides easy access to deliver contrast agents (a type of dye) for your computed tomography (CT) and/or magnetic resonance imaging (MRI) scan. The IV line is also used to deliver a small amount of sedation to help you relax. Most patients are awake but under light sedation during the procedure. Under certain circumstances (usually children), general anesthesia may be used.
  2. Next, a box-shaped head frame is attached to your head. The head frame is made of aluminum and weighs less than 2 pounds. The head frame helps exactly position your head so treatment can be planned and also helps position your head for the actual precisely focused treatment. Your surgeon positions the frame.
  3. You will receive four injections of a local anesthetic, one on each side of your forehead and two in the back of your head. These are the areas where specials pins will be placed to fasten the head frame to your skull. This keeps your head from moving. You may feel pressure as the pins are tightened, but this usually only lasts 5 to 10 minutes. After the head frame is positioned, a radiation therapist will take measurements of your head. These measurements are used for planning your treatment.
  4. Next, the CT and/or MRI are taken to determine the exact location of the lesion to be treated. The scanning usually takes about 30 minutes to complete.
  5. During the next 1 to 4 hours, based on the results of the scans and other information, your surgeon, the radiation oncologist, and other team members will plan your treatment on the computer. They will decide the area(s) to treat, radiation dose, and how to target the lesion for best results. During this time, you can remain in your room with family or friends.
  6. Next, your treatment is ready to begin.Your head frame will be attached to a bracket on the Gamma Knife® couch that will hold your head in the precise position for your treatment. The treatment team will go to another room while you receive your treatment, but you will constantly be observed by cameras. There is a microphone near your head so you will be able to easily talk with the staff during your treatment.
  7. The Gamma Knife® couch you lie on will slowly move into the Gamma Knife® machine that delivers the radiation. During treatment you will not feel or hear anything from the Gamma Knife® Most treatments take 30 minutes to 3 hours, depending on the size, shape, and location of the lesion and number of radiation doses (“shots”). After your treatment, the couch will move out and the staff will enter the room.
  8. Finally, your head frame will be removed. The pin sites will be cleaned with hydrogen peroxide and an antibiotic ointment and bandages will be applied. The IV will be removed.
  9. Under certain circumstances, repeat treatment in a few weeks or daily treatment over 3 to 5 days (where a special mask is used to position the head instead of the frame) may be recommended. Most patients require between one and five treatment sessions.

How will I feel during the Gamma Knife® procedure?

The actual Gamma Knife treatment is painless and nearly silent. Patients may listen to Internet radio or nap during the procedure.

What happens after the Gamma Knife ® procedure?

  • If you experience a headache after the frame is removed, you will be give you Tylenol®or Motrin® if needed. The IV will be removed.
  • Staff will review discharge instructions with you and your companion. You will be observed for 30 minutes to 1 hour after frame removal before being discharged. You will need an adult to drive you home.
  • It is recommended that someone stay with you the first night right after treatment to watch for any side effects from the procedure.
  • Keep your head elevated on a couple of pillows for 1 week. This will help to lessen swelling at the pin sites and minimize pressure within your head.
  • You may wash your hair/scalp 48 hours after your radiosurgery. This allows the pin sites to begin to heal and prevents infection from getting into the wounds.
  • You may take non-aspirin pain medication such as ibuprofen (Advil®, Motrin®) or acetaminophen (Tylenol®) if you are having any discomfort.
  • You may remove the bandages from the pin sites the morning after your radiosurgery. Clean the sites twice a day with hydrogen peroxide or mild soap and water. You may then apply a small amount of antibiotic ointment such as neosporin or bacitracin to the pin sites for 3 to 4 days. Applying bandages over the pin sites for 2 to 3 days is sufficient.

Risks / Benefits

What are the risks of Gamma Knife® radiosurgery?

Risks include:

  • Swelling of the brain
  • Headache
  • Nausea
  • Vomiting
  • Dizziness
  • Numbness
  • Hair loss near treated areas
  • Seizures
  • Weakness
  • Loss of balance
  • Vision problems
  • Other risks due to the underlying medical conditions of the patient

Recovery and Outlook

What’s the outlook after undergoing the Gamma Knife® procedure?

The success of the Gamma Knife® procedure depends on the size, location, type of lesion, your personal medical history, and other factors. You should discuss your expectations and outlook with your physician before treatment.

The goal of Gamma Knife® radiosurgery is that the radiation will cause the lesion to slowly shrink in size and then dissolve. You will have follow-up CT and/or MRI scans to check on treatment progress.

It may take weeks, months, a year (or sometimes longer) to see the effects of treatment. For example, pain relief for patient with trigeminal neuralgia can occur anytime between 1 day and 6 months, with most patients improving within 1 month. Cancerous tumors typically shrink over a period of weeks to months. Most noncancerous tumors stop growing immediately, but rarely shrink in size. Arteriovenous malformations may take 2 to 3 years to resolve after treatment.

When to Call the Doctor

When should I call the doctor after having the Gamma Knife® procedure ?

Call if you feel or notice any of the following symptoms:

  • Increased pain, redness, or swelling
  • The pin sites feel hot to the touch
  • A cloudy or foul smelling drainage is coming from the pin sites
  • Have a fever of 101 degrees F or higher

If you experience nausea, vomiting, severe headache, visual changes, difficulty speaking, a seizure, or any other symptom unusual for you, contact your physician immediately or go to the nearest emergency room.

Additional Details

The Gamma Knife® and Gamma Knife radiosurgery are considered by many to be the “gold standards” of stereotactic radiosurgery for brain lesions, providing results comparable to or better than conventional surgery in many cases, without the need for a surgical incision or protracted recovery in hospital.

Cleveland Clinic Neurosurgeons and Radiation Oncologists were the first to bring stereotactic radiosurgery to Ohio in August of 1989 using a modified linear accelerator. Their extensive experience in over 400 radiosurgery cases at Cleveland Clinic led them to conclude that the benefits of stereotactic radiosurgery would be available to more patients by offering Gamma Knife radiosurgery as an alternative or, in some cases as an adjunct, to conventional neurosurgical procedures. In its first year the Program treated 214 cases, making this the most successful first-year Gamma Knife Center in North America at that time. Our Gamma Knife Center is also one of only a handful of training centers world-wide certified by the manufacturer of the Gamma Knife for training of professionals for Gamma Knife radiosurgery procedures.

In July 2007, we were the second Center in the country to upgrade our equipment to the most technologically advanced model available, Leksell Gamma Knife® Perfexion™, which allows treatment in a wider range of anatomical structures, improves treatment planning, increases patient comfort and reduces treatment time. The new equipment, uses all image modalities, including PET, CT and MRI, as well as reduced treatment time. In 2014 more than 480 Gamma Knife procedures were performed.

The Novalis unit further increases the capabilities within radiation oncology and allows for radiosurgery and fractionated radiosurgery treatments for neuro-oncology patients using image guidance. This technology gives us the ability to treat lesions near critical structures, such as the optic nerves and chiasm, as well as retreat some patients who have undergone conventional radiotherapy. In general, the Gamma Knife is used for single treatments of focused radiation that conforms to the shape of small tumors or lesions, while the Novalis delivers fractionated conformal treatment for larger malignant or benign tumors.

Last reviewed by a Cleveland Clinic medical professional on 07/14/2017.


  • Expert knowledge and experience of healthcare providers at Cleveland Clinic Gamma Knife Center.
  • American College of Radiology and the Radiologic Society of North America. Gamma Knife. Accessed 5/22/2017.

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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy