Gamma Knife surgery represents one of the most advanced means available to manage brain tumors, arteriovenous malformations, and pain or movement disorders. Requiring no surgical incision to expose the target, the Gamma Knife can destroy deep-seated brain tumors and blood vessel malformations in the head once considered inoperable. It can also eliminate pain conditions and certain movement disorders, as well as silence malfunctioning areas of the brain precisely, to stop seizures or ease disabling pain problems that have not responded to other management strategies.
[Read how the Gamma Knife had a positive result in a patient in Why I let a brain tumor go untouched for 10 years from the Washington Post.]
The Center for Image-Guided Neurosurgery at the University of Pittsburgh Medical Center installed the first North American Gamma Knife in 1987 and subsequently introduced and pioneered each succeeding generation of technological improvement. Staffed by a highly skilled and productive team, we seek to provide rapid screening, scheduling, and completion of Gamma Knife radiosurgical procedures.
More than 19,000 patients have undergone radiosurgery in the department's Gamma Knife units since 1987. In September of 2007, the Perfexion® Gamma Knife unit was installed and in 2015 the Leksell Icon, encompassing the latest advances in radiosurgical technology, was installed.
The Gamma Knife Unit
The Gamma Knife contains 192 to 201 cobalt-60 sources of approximately 30 curies each, placed in a circular array in a heavily shielded unit. The unit directs gamma radiation very precisely to a target point. Such target points selected in the brain can be placed at the center of the radiation focus, allowing an effective radiation dosage to be delivered in one treatment session. The Gamma Knife has proved effective for thousands of patients with benign or malignant brain tumors, vascular malformations, pain or other functional problems.
Find out more about the Gamma Knife:
- Gamma Knife Technical Overview
- How was the Gamma Knife Technology Developed?
- What Makes Gamma Knife Treatment Superior to Others?
- What Can Patients Expect from the Gamma Knife?
- What are the Gamma Knife's Primary Uses?
- Professional Training
What Is Gamma Knife Radiosurgery?
Despite its name, Gamma Knife radiosurgery is not surgery. There are no knives and no incisions. It is a painless, noninvasive form of stereotactic radiosurgery (SRS) that uses many finely focused beams of gamma radiation to treat targets in the brain. The beams converge on the affected area while sparing surrounding healthy tissue, and the radiation dose is tailored to the individual condition. Because the procedure usually avoids incisions and general anesthesia, it can be a safer alternative to open surgery and can reach deep tumors, arteriovenous malformations, and other lesions that may not otherwise be operable. The goal of treatment is to stop tumor growth, and in some cases shrink tumors, or to close abnormal blood vessels.
Conditions Treated with the Gamma Knife
The Gamma Knife is used to treat a wide range of brain tumors and other brain conditions, including:
- Acoustic neuromas (vestibular schwannomas)
- Adenocarcinomas
- Arteriovenous malformations (AVMs)
- Astrocytomas
- Brain metastases
- Brain tumors
- Carotid cavernous sinus fistulas
- Cerebral cavernous malformations
- Craniopharyngiomas
- Dural arteriovenous fistulas
- Ependymomas
- Essential tremor
- Eye metastases
- Glioblastoma
- Gliomas
- Glomus tumors
- Hemangiopericytoma
- Meningiomas
- Pituitary tumors (pituitary adenomas)
- Parkinson's disease tremor
- Skull base tumors
- Trigeminal neuralgia
Who Is a Candidate for Gamma Knife Radiosurgery?
Several factors determine whether a patient is a candidate for Gamma Knife treatment, including age and overall health, symptoms, and the size, location, and complexity of the tumor or condition. Cases are evaluated by a multidisciplinary team that includes specialists in neurosurgery, radiation oncology, medical oncology, neuro-oncology, and nursing. The team reviews each case together to decide whether Gamma Knife or another approach is the best option.
What to Expect from Gamma Knife Treatment
Before the procedure
Patients may be asked to stop eating and drinking after midnight the night before treatment, and the nursing staff provides specific instructions. Patients should review all prescription medications with their physician to learn which to take or hold on the day of the procedure. On the day of treatment, patients should arrange for someone to drive them home, wear comfortable clothing, and avoid jewelry, makeup, nail polish, and hair products. Contact lenses, glasses, and dentures are removed before the procedure. Before treatment begins, the care team obtains high-definition MRI of the brain to map the exact location, size, and shape of the target. The procedure usually takes less than an hour, though complex cases may take longer.
During the procedure
Patients receive an IV and may be given medication to help them relax, but general anesthesia is not typically used and patients remain awake. The treatment itself is painless. The Gamma Knife can be delivered with either a frame-based or a frameless approach. In the frame-based approach, a lightweight metal frame is secured to the scalp and skull with small pins under local anesthesia and moderate sedation to keep the head still. In the frameless approach, a custom-contoured mask holds the head in position and typically requires no sedation or local anesthesia. During treatment, the patient lies on a table that moves into the unit, the care team monitors the patient from an adjacent room by camera and intercom, and nearly 200 beams of radiation converge on the target. The patient feels nothing as the radiation is delivered.
Recovery after the procedure
Once treatment is complete, the care team removes the frame or mask and bandages any pin sites. Patients are monitored in a recovery area and can usually eat and drink soon afterward. A headache after frame removal can be managed with medication. Most patients return home the same day and resume normal activities, including work, within a day or so. Mild side effects such as fatigue may last several days but generally resolve quickly. Symptoms related to the treated condition typically improve over time. Follow-up imaging is required, and depending on the condition a patient may need one session or several.
Risks and Side Effects
Short-term side effects after Gamma Knife treatment may include fatigue, headache, nausea, scalp irritation or soreness at the pin sites, swelling in the treated area, and temporary hair loss. Long-term complications are rare but can include brain swelling, infection, seizures, and vision or hearing loss. These complications are uncommon and can usually be treated with medication. Patients should contact their physician about seizures or other unexplained symptoms after treatment.
Treatment Outcomes
Outcomes after Gamma Knife radiosurgery depend on the condition being treated. General results include:
- Acoustic neuroma: treatment can limit growth or reduce tumor size with little risk of lasting nerve damage.
- Arteriovenous malformation (AVM): blood vessels in the AVM can thicken and close.
- Brain tumors: treatment damages the genetic material in the tumor's cells so they can no longer reproduce; the cells inactivate and the tumor may gradually shrink.
- Pituitary and skull base tumors: treatment can shrink the tumor and reduce disruption of pituitary hormones.
- Trigeminal neuralgia: treatment alters the nerve fibers that cause intense facial pain.
Since 1987, more than 19,000 Gamma Knife treatments have been performed for patients with benign or malignant brain tumors, pain and movement disorders, vascular malformations, and other functional problems. More than 1,500 of these patients had arteriovenous malformations, and treatment closed 70% to 90% of AVMs within three years. More than 1,600 procedures were performed for acoustic neuroma, a tumor on the nerve connecting the inner ear to the brain that can cause deafness; treatment prevented tumor growth in 97% of patients, and up to 80% retained their hearing over the long term.
Current Gamma Knife Technology
The Center for Image-Guided Neurosurgery operates two Gamma Knife units, the Gamma Knife Esprit and the Gamma Knife Icon, making it one of only a few centers worldwide with two units. The Gamma Knife Esprit is among the most advanced units available and incorporates artificial intelligence, advanced robotics, and other refinements. Together, the Esprit and Icon support both frame-based and frameless radiosurgery, provide dosage control and motion-management systems for highly accurate delivery, and use radiological imaging to target areas of the brain with sub-millimeter precision. Faculty in the Center perform about 600 Gamma Knife procedures each year, and the Center remains a major teaching site for neurosurgeons, radiation oncologists, medical physicists, and nurses from around the world.