Gamma Knife Surgery

Gamma Knife surgery is a painless, computer-guided form of radiation therapy. This treatment delivers highly focused beams of energy on tumors or lesions in your brain and upper spine. It commonly treats small brain tumors, arteriovenous malformations, trigeminal neuralgia and more.


Gamma Knife

What is Gamma Knife surgery?

Gamma Knife® surgery is a type of noninvasive radiation therapy that uses computer-guided planning to treat brain and upper spine conditions and tumors. The Gamma Knife delivers beams of highly focused energy to a specific treatment area. This type of radiation minimizes harm to the surrounding tissue.

Despite its name, this procedure isn’t a surgery and doesn’t involve any knives. Gamma Knife gets its name based on the precision of gamma rays. These are high-energy photons (a particle of electromagnetic radiation). Gamma rays are as accurate as a surgical knife to specifically target an area of your brain without cutting into your body.

Gamma Knife surgery is a type of stereotactic radiosurgery. It’s also known as Gamma Knife radiosurgery and Gamma Knife radiation.

What does Gamma Knife surgery treat?

The goal of Gamma Knife surgery is for the radiation to stabilize, shrink or destroy a tumor or lesion. Gamma Knife surgery can treat small brain abnormalities like:

Common types of tumors Gamma Knife surgery treats include:

Some of the most common conditions that Gamma Knife surgery treats include:

The Gamma Knife may be helpful if you have a brain lesion or tumor that a surgeon can’t reach with traditional surgical techniques or if you’re unable to undergo surgery for any reason. You can also combine Gamma Knife surgery with traditional surgery to prevent tumor regrowth.


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

Procedure Details

How should I prepare for Gamma Knife surgery?

Before Gamma Knife surgery, you’ll meet with a healthcare provider. This could be a neurosurgeon and/or radiation oncologist. They’ll first perform a physical exam. During this exam, let your healthcare provider know if you have any medical implants like a pacemaker, cochlear implant, an implanted medication pump or nerve stimulator, among others.

Your provider will ask if you have any allergies. They’ll also ask you if you’re able to lay flat on your back for 30 to 60 minutes, as it’s required for the procedure. This can be difficult to do if you have lung disease or esophageal reflux.

You’ll receive instructions to prepare for Gamma Knife surgery that are specific to your situation. In general, these instructions might include:

  • Don’t eat or drink anything after midnight the evening before your procedure.
  • Take your morning medications with sips of water. Bring all prescribed and over-the-counter (OTC) medications, including inhalers, with you.
  • Wash your scalp the night before your Gamma Knife procedure. Wear your hair loose. Don’t use clips, pins or bands in your hair the day of your procedure.
  • Wear easy-to-remove shoes and comfortable, loose-fitting clothing. Avoid wearing a shirt that must be put on or taken off over your head.
  • You’ll need to ask someone to drive you to and from your procedure.

If you have any questions, a good time to ask is during your pre-treatment exam.

What’s the difference between a frame and a frameless Gamma Knife?

There are two types of Gamma Knife systems available:

  • Frame: A fitted metal (usually aluminum) band goes around your head. The frame prevents your head from moving and helps guide gamma rays to a specific area of your brain.
  • Frameless: A thermoplastic mask rests over your face, or a net fits around your head. The mask secures to an existing frame on the Gamma Knife table, so your head is completely still.

These pieces of the Gamma Knife machine seem the most intimidating. The frame needs to attach to your skull, but don’t worry — your provider will numb up that area. The mask or net rests on your face during the entire procedure. Your provider will give you medications to help you relax and stay still.

Gamma Knife frame fitting

Before Gamma Knife surgery that uses a frame, a neurosurgeon will fit one to your head. To do this, they’ll:

  • Position the frame on your head. The metal frame weighs less than 2 pounds.
  • Give you four injections of a local anesthetic. The injections will be on each side of your forehead and in the back of your head. The anesthetic makes it so you won’t feel pain during pin placement.
  • Place pins. Pins hold the frame in place on your skull. You might feel light pressure as the pins tighten.

Your head doesn’t need to be shaved to wear a frame.

Frameless Gamma Knife procedures don’t require a frame fitting.


What happens during Gamma Knife surgery?

On the day of your procedure, the following steps prepare you for a Gamma Knife procedure:

  1. IV: You’ll receive an IV in a vein in your arm. The IV delivers a contrast agent (a type of dye) that helps with imaging tests. The IV can also deliver a small amount of sedatives to help you relax if needed. General anesthesia might be an option for children (so they’ll be asleep).
  2. Imaging tests: Your care team will perform imaging tests like a computed tomography (CT) and/or magnetic resonance imaging (MRI) scan. Imaging determines the exact size and location of the affected area of your brain where the procedure will be done. The scanning usually takes about 30 minutes.
  3. Procedure planning: Your care team (a neurosurgeon, a radiation oncologist, medical physicist and other team members) plan your treatment on a computer. They’ll decide the area(s) to treat, the radiation dose and how to target the lesion for best results based on what they found on the imaging test. This can take up to an hour.

The steps of a Gamma Knife procedure include:

  1. Fitting a frame on your head or using frameless options. A neurosurgeon will secure the frame or frameless option to your head and the Gamma Knife table.
  2. Lying on a table. The table moves into the Gamma Knife machine that delivers radiation.
  3. Receiving radiation. The machine may move your body and head slightly so the radiation can reach all treatment spots. You’ll move out of the Gamma Knife machine when the procedure is done.
  4. Removing the frame or frameless option from your head.
  5. Removing the IV from your arm.

Your care team will be immediately outside the room while you receive your treatment, but you’ll never be alone during the procedure. Your team will monitor you constantly. There will be a microphone near your head so you can talk with your care team during your treatment if necessary.

Does Gamma Knife surgery hurt?

No. You won’t feel any pain or discomfort during the procedure. The machine doesn’t produce any heat. You won’t hear any noise. A healthcare provider may give you sedatives to help you relax and stay still. Many people take a nap during the procedure.

How long does Gamma Knife surgery take?

Gamma Knife surgery itself takes between 30 minutes to two hours. It varies based on the size, shape and location of the affected area of your brain that needs treatment.

You should plan to spend several hours (up to 12) at the treatment center. Your care team will discuss the best timeframe for your situation before the date of your procedure.

What happens after Gamma Knife surgery?

After the procedure, you’ll feel a little groggy and drowsy from the relaxation medicine given when a frame is used. You should have someone drive you home from the procedure if a frame is necessary. You can go home the same day unless a healthcare provider recommends you stay overnight in the hospital for monitoring.

You should be able to get back to your regular activities like work and school the next day.

Your provider will give you instructions to follow to take care of yourself at home. For a frame, these instructions could include:

  • Keep your head elevated on a couple of pillows for one week.
  • Remove bandages on your head the day after your procedure. Clean the sites twice a day and apply a small amount of antibiotic ointment for three to four days.
  • Wash your hair/scalp 48 hours after the procedure.
  • Take non-aspirin pain medication such as ibuprofen (Advil®, Motrin®) or acetaminophen (Tylenol®) if you have any discomfort.


Risks / Benefits

What are the benefits of Gamma Knife surgery?

The benefits of Gamma Knife surgery include but aren’t limited to the following:

  • It doesn’t require incisions (cutting into your skin).
  • It safely reaches tumors or lesions deep within your brain that traditional surgery can’t reach.
  • The procedure can target multiple tumors and lesions at the same time.
  • It limits damage to surrounding tissue.
  • Recovery time is quick.

How successful is Gamma Knife surgery?

Gamma Knife surgery is a successful and effective procedure to treat small tumors and other brain lesions. One study reported that the tumor control rate was 95%. Tumor control refers to the destruction of tumor cells that affect their growth.

The success of the Gamma Knife procedure depends on the size, location, type of lesion and your general health at the time of the procedure, among other factors. Your care team will discuss their expectations and outlook for your situation before the procedure begins so you can make an informed decision about your health.

Depending on the reason for the procedure, you may or may not need additional Gamma Knife treatment or traditional surgery. You’ll have follow-up CT and/or MRI scans to check on treatment progress.

What are the risks or complications of Gamma Knife surgery?

While risks related to the procedure are typically low, risks and/or side effects of Gamma Knife surgery may include:

Severe (but rare) complications can include:

Call 911 or your local emergency services number immediately if you notice severe symptoms or have trouble breathing.

Possible brain swelling can happen immediately after, or months after, the procedure. Your care team may give you medications to prevent this complication from happening before and after the procedure.

Recovery and Outlook

Benefits to Gamma Knife

What is the recovery time for Gamma Knife surgery?

The recovery time is quick after Gamma Knife surgery. In most cases, you can get back to your normal activities the next day, without interruption. Your provider may ask you to limit strenuous activities for a few days following the procedure. Your provider will give you the best outlook on your recovery time.

When will I know if Gamma Knife surgery was successful?

It may take weeks, months, a year or sometimes longer to see the full effects of treatment. For example, if you have trigeminal neuralgia, pain relief can occur anytime between one day and six months, with most people improving within one month. Cancerous tumors typically become stable or get smaller over a period of weeks to months. Many noncancerous tumors stop growing immediately but don’t get smaller. Arteriovenous malformations may take two to three years to resolve after treatment.

How many Gamma Knife treatments do I need?

Your healthcare provider will let you know what your treatment plan looks like. Depending on the type and size of the tumor or lesion, you might need more than one treatment session. Follow-up imaging tests can give your provider more information on the results of the procedure to plan for additional treatments if necessary.

What is the life expectancy after Gamma Knife surgery?

Your life expectancy varies based on many factors like your general health at the time of treatment, condition stage, and tumor size and location, for example. While Gamma Knife surgery is safe and effective, it doesn’t cure all conditions. In some cases, it can prolong your life expectancy. If complications arise, it can affect your outcome. A healthcare provider will give you the best outlook based on your situation.

When To Call the Doctor

When should I call my healthcare provider?

Contact your healthcare provider if you feel or notice any of the following symptoms:

  • The pin sites feel hot to the touch (if you’ve had the head frame).
  • A cloudy or foul-smelling drainage is coming from the pin sites.
  • You have a fever.

If you experience any of the following symptoms, contact your physician immediately or go to the nearest emergency room:

  • Nausea.
  • Vomiting.
  • Severe headache.
  • Visual changes.
  • Difficulty speaking.
  • A seizure.
  • Any other symptom that’s unusual for you.

A note from Cleveland Clinic

Gamma Knife surgery is a highly effective treatment with minimal negative effects. Because of its ability to stabilize or reduce the size of a tumor or lesion, you might only need one treatment. However, you may need additional Gamma Knife surgeries depending on your situation. If you have any questions about the procedure, let your care team know. They’ll walk you through what to expect so you feel more comfortable undergoing treatment.

Medically Reviewed

Last reviewed on 03/07/2024.

Learn more about our editorial process.

Cancer Answer Line 866.223.8100