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Stereotactic radiosurgery - Gamma Knife

Stereotactic radiotherapy; Stereotactic radiosurgery; SRT; Fractionated stereotactic radiotherapy; SRS; Gamma Knife; Gamma Knife radiosurgery; Non-invasive neurosugery; Epilepsy - Gamma Knife


Stereotactic radiosurgery (SRS) is a form of radiation therapy that focuses high-power energy on a small area of the body.

Despite its name, radiosurgery is a treatment, not a surgical procedure. Incisions (cuts) are not made on your body.

More than one system is used to perform radiosurgery. This article is about Gamma Knife radiosurgery.



Gamma Knife radiosurgery is done only for tumors and other medical problems of the head. For tumors and problems elsewhere in the body, other radiosurgery systems may be used.

Before treatment, you are fitted with a head frame. The frame is attached to your scalp. This is done using 4 small pins or anchors that go through your skin to the surface of your skull. Medicine is first given to numb the areas where the pins or anchors attach.

The frame keeps your head steady during treatment. It also helps your doctors ensure the energy beams are aimed at the exact spot in your head that needs treatment.

After the frame is attached to your head, imaging tests such as CT , MRI , or angiogram are done. The images show the exact location, size, and shape of your tumor or problem area.

During treatment:

  • You will not need to be put to sleep. The treatment does not cause pain.
  • You lie on a table that slides into a machine that delivers radiation.
  • The head frame is attached to a helmet that has many holes. The energy beams are delivered through these holes.
  • The machine may move your head so that the energy beams are delivered to the exact spots that need treatment.
  • The health care providers are in another room. They can see you on cameras and hear you and talk with you on microphones.

Each treatment takes a few minutes to 2 hours. You may receive more than one treatment session. Most often, no more than five sessions are needed.


Why the Procedure Is Performed


SRS targets and treats an abnormal area. This minimizes damage to nearby healthy tissue.

Gamma Knife radiosurgery is used to treat the following types of brain tumors:

  • Cancer that has spread (metastasized) to the brain from another part of the body
  • A slow-growing tumor of the nerve that connects the ear to the brain ( acoustic neuroma )
  • Pituitary tumors
  • Tumors that are not cancer (chordoma, meningioma)

Gamma Knife is also used to treat other problems of the brain:

  • Blood vessel problems ( arteriovenous malformation , arteriovenous fistula )
  • Some types of epilepsy
  • Trigeminal neuralgia (severe nerve pain of the face)
  • Severe tremors due to essential tremor or Parkinson disease




Radiosurgery may damage tissue around the area being treated. As compared to other types of radiation therapy, Gamma Knife treatment is much less likely to damage nearby healthy tissue.

Brain swelling may occur. Swelling usually goes away without treatment. Some people need medicine to control this swelling. In rare cases, surgery with incisions (open surgery) is needed to treat the brain swelling caused by the radiation.

The spots where the head frame is attached to your scalp may be red and sensitive after treatment. This should go away with time.


Before the Procedure


The day before your procedure:

  • DO NOT use any hair cream or hair spray.
  • DO NOT eat or drink anything after midnight unless told otherwise by your doctor.

The day of your procedure:

  • Wear comfortable clothing.
  • Bring your regular prescription medicines with you to the hospital.
  • DO NOT wear jewelry, makeup, nail polish, or a wig or hairpiece.
  • You will be asked to remove contact lenses, eyeglasses, and dentures.
  • You will change into a hospital gown.
  • An intravenous (IV) line will be placed into your arm to deliver contrast material, medicines, and fluids.


After the Procedure


Often, you can go home the day of treatment. Arrange ahead of time for someone to drive you home. You can go back to your regular activities the next day if there are no complications such as swelling. If you have complications, you may need to stay in the hospital overnight for monitoring.

Follow instructions for how to care for yourself at home .


Outlook (Prognosis)


The effects of Gamma Knife radiosurgery may take weeks or months to be seen. The prognosis depends on the condition being treated. Your provider will monitor your progress using imaging tests such as MRI and CT scans.




Baehring JM, Hochberg FH. Primary Nervous System Tumors in Adults. In: Dariff RB, Jankovic J, Mazziotta JC, Pomeroy SL, eds. Bradley's Neurology in Clinical Practice . 7th ed. Philadelphia, PA: Elsevier; 2016:chap 74.

Brown PD, Jaeckle K, Ballman KV, et al. Effect of radiosurgery alone vs radiosurgery with whole brain radiation therapy on cognitive function in patients with 1 to 3 brain metastases: a randomized clinical trial. JAMA . 2016;316(4):401-409. PMID: 27458945 www.ncbi.nlm.nih.gov/pubmed/27458945 .

Elekta AB. Gamma Knife radiosurgery patient resource center. 2015. www.elekta.com/patients/gammaknife-treatment-process.html . Accessed August 9, 2016.

Romanelli P, Morris DE, Adler JR Jr, Ewend MG. Image-guided robotic radiosurgery. In: Winn RH, ed. Youmans Neurological Surgery . 6th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 257.

Welling DB, Spear SA, Packer MD. Stereotactic radiation treatment of benign tumors of the cranial base. In: Flint PW, Haughey BH, Lund V, Niparko JK, Robbins KT, eds. Cummings Otolaryngology: Head & Neck Surgery . 6th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 179.


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          Review Date: 5/4/2015

          Reviewed By: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Internal review and update on 09/01/2016 by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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