What Medical Conditions Can a Gamma Knife Procedure Treat?

Single-dose radiation treats certain brain conditions without surgery

Gamma Knife radiosurgery is an advanced surgical technique in which a highly focused beam of radiation is used to precisely destroy areas of tissue. Although it is called surgery, a Gamma Knife procedure involves neither incisions nor a scalpel.

The procedure is far less invasive than conventional surgery and offers greater precision when performing delicate operations, primarily on the brain. Because of this, Gamma Knife surgeries can often be performed on an outpatient basis or with an overnight hospital stay.

Gamma knife
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Stereotactic radiosurgery was first developed in 1949 by Swedish neurosurgeon Lars Leskell with the aim of treating small areas of the brain without damaging adjacent tissue.

Leskell’s early designs for the device used X-ray, proton, and later gamma rays to deliver a narrow beam of radiation to a targeted point on the brain. By directing radiation from multiple angles, the converging beams could deliver a lethal dose to destroy tumors, block nerves, or close off blood vessels with minimal collateral damage.

Leskell officially introduced the Gamma Knife in 1968. By the 1970s, the Gamma Knife was fully stereotactic (three-dimensional in approach) with the introduction of magnetic resonance imaging (MRI) and computed tomography (CT) scans. The first Gamma Knife was only brought the United States in 1979 in an arrangement between Leskell and the University of California, Los Angeles.

The Gamma Knife is today the registered trademark of Elekta Instruments, Inc. in Stockholm, Sweden.

Similar Radiosurgical Devices

In addition to the Leskell device, a similar tool called a linear particle accelerator (Linac) was invented in 1952 as a form of fractionated (multi-dose) radiation therapy. It was only in 1982 that refinements to the device allowed it to be used in radiosurgery.

The Linac device differs from the Gamma Knife in that it is used primarily for radiation therapy in multiple parts of the body. The Gamma Knife, by contrast, is used almost exclusively for the brain radiosurgery. Moreover, the Linac device requires far greater technology and expertise if used for radiosurgery and delivers a far wider beam compared the Gamma Knife (1.1 millimeters versus 0.15 millimeters, respectively).

A newer concept called the Linac Cyberknife was introduced in 2001 and largely mimics the Gamma Knife in concept. The device, mounted on a robotic arm, delivers targeted radiation from multiple angles but, unlike the Gamma Knife, has not demonstrated improved survival rates when compared to other forms of cancer radiation therapy.

A final type of radiosurgery, known at proton beam therapy (PBT), uses a beam of proton particles to irradiate diseased tissue. However, a 2012 study from the American Society of Radiation Oncology concluded that PBT offered no benefits over conventional forms of radiation therapy with the exception of pediatric cancers of the central nervous system, severe eye melanoma, and chordomas (a type of bone cancer).

Despite the potential benefits of PBT, the exceptional cost of the system (between $100 to $180 million) makes it an impractical option for most hospitals.

Conditions Treated

Gamma Knife radiosurgery is most often used to treat tumors and other lesions in the brain. But it can also be effective in treating certain pain and movement disorders as well as vascular abnormalities in the brain.

The Gamma Knife is primarily used to treat the following conditions:

  • Brain metastases (cancers that have spread to the brain from tumors in other organs)
  • Glioblastoma (a type of brain cancer)
  • Acoustic neuroma (a noncancerous tumor on the nerve leading from the inner ear to the brain)
  • Meningioma (a typically noncancerous tumor that arises from the membranes surrounding the brain and spinal cord)
  • Pituitary adenoma (a noncancerous tumor of the pituitary gland)
  • Cushing's disease (a serious condition of an excess of the steroid hormone cortisol in the blood level caused by a pituitary tumor secreting adrenocorticotropic hormone (ACTH). ACTH is a hormone produced by the normal pituitary gland).
  • Trigeminal neuralgia (a condition in which pressure on the trigeminal nerve causes extreme facial pain)
  • Essential tremor (a neurological disorder that causes involuntary and rhythmic shaking, unrelated to Parkinson's disease)
  • Arteriovenous malformation, or AVM (the abnormal connection between arteries and veins, usually in the brain or spine)

Gamma Knife radiosurgery may be used in situations where the brain lesion cannot be reached by conventional surgery or in persons who cannot tolerate an open surgical procedure such as craniotomy.

Because the beneficial effects of a Gamma Knife procedure manifest slowly over time, it is not used for people whose condition requires immediate or urgent treatment.

How It Works

The Gamma Knife procedure is called a "surgery" because it can be performed in one session with the same clinical aims of a regular operation. The effects of the Gamma Knife differs by the type of disease being treated:

  • When used to treat tumors, the focused radiation disrupts the DNA in tumor cells. This interferes with the cell's ability to replicate, causing the tumor to shrink.
  • When used to treat neurological disorders, recent findings show that the beam of radiation causes remodeling of glial cells and has a neuromodulatory effect.
  • When used to treat AVM, the Gamma Knife can reduce the size and volume of blood flowing through a vessel, thereby reducing the risk of a rupture or stroke.

The machine itself is similar in design to an MRI or CT scan with a flatbed and a tube-like dome into which your head is placed. It is not as deep as the other machines, however, and is completely silent so that you are less likely to experience claustrophobia.

What to Expect

A Gamma Knife procedure typically involves a treatment team, including a radiation oncologist (a cancer healthcare provider specializing in radiation), a neurosurgeon, a radiation therapist, and a registered nurse. The procedure can differ slightly depending on the treated condition but is usually performed in the following steps:

  1. When you arrive for treatment, you would be asked to lie down on the flatbed after which either a mesh-like mask or a lightweight head frame would be used to stabilize your head and keep it from moving.
  2. An MRI or CT scan would then be performed to pinpoint the exact location and dimensions of the targeted structure or abnormality.
  3. Based on the results, the team will formulate a treatment plan including the precise number of exposures and beam placement.
  4. After being positioned in place, your head would be moved into the dome, and the radiation treatment would begin. You would be fully awake and connected to your healthcare providers through an audio connection. Depending on the condition, the procedure could take anywhere from a few minutes to more than an hour.

Treatment Side Effects

While the Gamma Knife procedure itself is painless, the use of radiation can sometimes cause side effects due mainly to brain inflammation. The severity of symptoms tends to be associated with the duration and location of the radiation treatment and may include:

  • Headache
  • Numbness
  • Nausea
  • Blurry vision
  • Weakness
  • Loss of balance
  • Hair loss (usually temporary)
  • Seizures

There may be other risks associated with your specific medical condition. Be sure to speak with your healthcare provider about this before undergoing a Gamma Knife procedure.


Gamma Knife radiosurgery has proven effective in treating benign or malignant tumors up to four centimeters (roughly 1½ inches) in size. For people with metastatic brain cancer, the procedure is seen to be effective in providing tumor control and extending survival times.

Success rates vary by the condition being treated, as follows:

  • With regards to AVM, radiosurgery is considered the primary form of treatment today and has a cure rate of between 54 percent and 92 percent depending on the location of the vessel.
  • Meanwhile, a 2016 study from Europe reported that people with trigeminal neuralgia benefited significantly from the procedure, with 81% remaining pain-free for three years and 76 remaining pain-free for seven years.
  • Similarly, a 2012 Japanese study reported that from 53 patients treated for essential tremors who completed 24 months of follow-up, 43 were evaluated as
  • having excellent or good results (81%).
  • A 2013 study from the University of Virginia School of Medicine demonstrated that the Gamma Knife procedure resulted in 70% of the patients being cured of Cushing's disease after a median duration of observation of 48 months.
  • Acute complications following Gamma Knife radiosurgery are considered rare, with most related to the underlying condition rather the procedure itself.
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By James Myhre & Dennis Sifris, MD
Dennis Sifris, MD, is an HIV specialist and Medical Director of LifeSense Disease Management. James Myhre is an American journalist and HIV educator.