Gamma Knife surgery is computer-guided radiation therapy. Despite its name, it does not require an incision. There are no knives involved. Gamma Knife is a brand name.

The procedure uses highly focused gamma radiation beams to target tumors, lesions, and other conditions of the brain. Sometimes, the procedure is used when other treatment options have not worked. Gamma Knife surgery may also be the first treatment choice for some conditions.

Gamma Knife surgery is only one type of stereotactic radiosurgery. This is a powerful and precise radiation therapy that most often involves just one treatment of a high dose of radiation in a very focused area. In some instances, it may involve more than one treatment.

This article describes Gamma Knife surgery and looks at risks, side effects, and how effective it may be.

Gamma Knife surgery may be used to treat:

People with multiple brain tumors or lesions may not be good candidates for Gamma Knife surgery because of the high radiation exposure risk.

Depending on your health condition, Gamma Knife surgery may be one of many treatment options, or it may be considered the best option because of the risks associated with other treatments.

Some people may find that Gamma Knife surgery is an option after trying other treatments without success.

If you’re a candidate for Gamma Knife surgery, a doctor will review your treatment options, explain them to you, and review the possible side effects.

Gamma Knife surgery takes only a few hours, but it will take some days and weeks to prepare for it and care for afterward. Here’s a closer look at what to expect before, during, and after Gamma Knife surgery.


In the days and weeks before Gamma Knife surgery, you will meet with some doctors who will conduct the procedure. This team may include a neurosurgeon and radiation oncologist, plus their staffs.

They will most likely:

  • conduct a physical exam
  • take a full medical history
  • request imaging tests, including CT and MRI scans

The day before the procedure, you’ll need to:

  • avoid food or drink after midnight
  • wash your hair and scalp
  • make sure you have someone who can drive you home after the procedure

During the procedure

Gamma Knife surgery will typically include the following steps:

  • Once you arrive at the hospital, you’ll be taken to a pre-procedure room. The care team will ask you to remove your clothing and put on a hospital gown. You may also need to have a small portion of your hair trimmed near the radiation site, but that’s not always the case.
  • You will be fitted for a rigid head frame. This device ensures the radiation beams go where they should. For this fitting, a doctor will administer four local anesthetic injections. This will numb the points where the head frame is attached.
  • You will get an IV. This will allow the team to administer contrast dye for imaging tests. They may also give you sedation medication or general anesthesia.
  • Once the head frame is in place, the doctors will take measurements with a CT or MRI scan. They will then develop the three-dimensional image that will guide the Gamma Knife surgery. They will determine the areas to treat, the radiation dose they will use, and how they will approach the targeted area of the brain.
  • After the treatment plan is finalized, the head frame will be secured to a table.
  • The table slides into the Gamma Knife machine. The treatment team will leave the room but will be watching at all times with video cameras. They’ll be able to speak to you through an intercom.
  • The treatment usually lasts 1 to 2 hours, but sometimes, it may last only about 30 minutes. It can also take longer, up to 3 to 4 hours, if necessary.
  • Once the treatment is over, the table slides out of the machine, and the head frame and IV are removed. You will then be sent to a recovery room.


Because Gamma Knife surgery is not actual surgery, recovery is much faster. You can expect the following:

  • In the recovery room, nurses or other care providers will clean the pin sites on your head with hydrogen peroxide and apply an antibiotic ointment.
  • You will stay in the room for at least 30 minutes, maybe longer, so the team can monitor your recovery.
  • In most cases, you will be discharged the same day. Unless there are complications, you will not need to stay overnight.
  • You can wash your hair 48 hours after the procedure. But you will need to continue to clean the pin sites and use antibiotic ointment or cream until the sites are fully healed.

Gamma Knife surgery is a low risk procedure, especially compared to traditional brain surgery. The most common risks and side effects of Gamma Knife surgery include:

When to get immediate medical attention

After the surgery, contact your doctor immediately or go to an emergency room if you experience:

  • severe headache
  • visual changes
  • difficulty speaking
  • a seizure
  • a fever over 101°F

If the pin sites are hot to the touch or show signs of discharge, you should contact your doctor. You may have an infection and need additional medication.

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If you’re considering Gamma Knife surgery, there are several potential benefits.


  • No incision or cutting.
  • General anesthesia is usually not needed.
  • Reduces the risk of postsurgery complications, including infection and bleeding.
  • The surrounding healthy tissue is spared.
  • Can target tumors deep inside the brain that traditional surgery cannot reach.
  • Can target multiple tumors at the same time.
  • Post-treatment discomfort and pain are minimal.
  • No overnight stay is required.
  • Return to usual activities is quick, usually in 2 to 3 days.
  • Can be combined with other treatment options, including traditional surgery.
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It’s also important to consider the potential drawbacks of Gamma Knife surgery.


  • The treatment effect is not always immediate.
  • Radiation-induced toxicity is possible.
  • It may not be the best choice for people with multiple tumors or lesions.
  • The possibility of severe side effects.
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Gamma Knife surgery is often successful. The goal of the procedure is typically to shrink, stabilize, or destroy a brain tumor or lesion.

However, Gamma Knife surgery’s outcome or success rate depends on the condition. In the case of a brain tumor, the size of the tumor and its location can affect the outcome.

In one study, 91.75% of patients with trigeminal neuralgia were pain-free in a median period of only 10 days. Three years after the Gamma Knife surgery, 71.8% of them remained pain-free.

After the procedure, you can expect to have follow-up CT or MRI scans regularly. You’ll likely continue to meet with your oncology team or neurologist regularly. It may take several weeks or longer to see the full impact of the treatment.

Gamma Knife surgery can effectively treat certain brain tumors, lesions, or other conditions that originate in the brain. It is often preferred over traditional brain surgery because it doesn’t require incisions and has fewer adverse effects.

Also, in most cases, you will need only one treatment because it often successfully reduces or stabilizes the tumor or lesion.

If you’re interested in Gamma Knife surgery or wonder whether it may be a treatment option for you, talk with your doctor or neurologist. They can refer you to a neurosurgeon who can recommend a treatment plan.