About Gamma Knife®
Patients Benefit from Gamma Knife® Radiosurgery
Radiosurgery is being used by the Center's neurosurgeons and radiation oncologists to help patients with benign and malignant brain tumors and arteriovenous malformations (AVMs). It is also useful for controlling face pain caused by trigeminal neuralgia. Indications for radiosurgery include one or more of the following:
- A medical condition that places a patient at unacceptably high risk for anesthesia and open microsurgery
- Advanced age
- A lesion located within a critical brain region in which an open operative approach would likely cause a significant neurological deficit
- A recurrent or persistent tumor that was not eradicated by open neurosurgery and has not responded to external beam radiation therapy
- A patient who does not wish to undergo traditional microsurgery
- The physician's assessment that radiosurgery could control the tumor as well as surgery, yet offers a lower risk of complications
Radiosurgery is not intended to replace conventional neurosurgery in all instances. Gamma Knife treatment may serve as an adjunct to standard neurosurgical therapy or as the preferred course of treatment when traditional surgery is not recommended. Some of the conditions that can be treated with the Gamma Knife include:
Arteriovenous Malformations (AVMs)
Arteriovenous malformations are made up of abnormal arteries and veins, which in most cases form prior to birth. AVMs may cause headaches, seizures and bleeding within the brain. If spontaneous bleeding occurs, a person may experience a stroke with paralysis, coma or possibly death. Most AVMs should be treated to reduce or eliminate these risks.
Obliteration or closing off of the AVM vessels after Gamma Knife radiosurgery occurs gradually over two to three years. The success rate varies between 65 and 100 percent depending on the size and location of the AVM. Permanent neurological problems, as a complication of treatment, occur in fewer than five percent of patients. Because Gamma Knife treatment results in a gradual closing off of the abnormal vessels, the AVM can still bleed in the interval between treatment and total obliteration. Periodic MRI scans are obtained (usually at one year intervals) to monitor patient progress.
Acoustic Neuroma (Vestibular Schanoma)
Acoustic neuromas are benign tumors of the eighth cranial nerve in the brain. These tumors usually cause hearing loss, ringing in the ears or balance problems. The Gamma Knife can be used to stop the tumor's growth. Without treatment, acoustic tumors will eventually cause deafness in most patients. Treatment has resulted in elimination of further tumor growth or reduction in tumor size in more than 90 percent of patients. Useful hearing can be preserved in about 35 percent of Gamma Knife cases but progressive hearing loss can occur after treatment. Permanent weakness of the face is very rare and occurs in fewer than one percent of cases. Perioidic MRI scans are obtained (one to three year intervals) to monitor patient progress.
Metastatic Brain Cancer
Brain metastasis is the most common indication for Gamma Knife radiosurgery. Radiosurgery for metastatic brain tumors may be used in conjunction with other therapies including conventional open skull surgery and whole brain radiation therapy depending on the size, location and number of tumors. The best tumor size for Gamma Knife treatment is less than three centimeters (about one inch) and more than one tumor can be treated during a single Gamma Knife session. Gamma Knife treatment has resulted in tumor control (elimination of further growth, tumor shrinkage or obliteration) in about 90 percent of cases. Patients should ask their doctor about possible side effects of treatment as they relate to the specific type and location of their tumor. Since there is a small risk for recurrence at previously treated sites and the possibility of developing new metastasis after treatment, progress is monitored with MRI scans every three months.
Trigeminal Neuralgia (Tic Douloureaux)
Trigeminal neuralgia is manifested by unpredictable, repeated, severe attacks of face pain that are often provoked by normal activities such as eating, talking or touching the face. Touching a "trigger area" or sensitive spot commonly provokes the pain. Trigeminal neuralgia may affect the forehead, cheek lower jaw or any combination of these areas. There may be long periods of remission (periods without pain) between attacks. Over time the attacks usually become more frequent and persistent. Gamma Knife radiosurgery is one option for treating trigeminal neuralgia. Numbness of a portion of one side of the face may occur rarely after treatment. The physician should review all available therapies to help the patient decide which type of treatment may be best for each individual circumstance.
Other Brain Tumors
Other brain tumors that may benefit from Gamma Knife radiosurgery include glioblastoma multiforme, oglioendroglioma, astrocytomas, meningiomas, pituitary tumors, and skull base tumors. Patients should consult with their doctor about complications from the treatment of these tumors as they relate to the type and location of their tumor.
Risks of Gamma Knife Surgery
As with any operation, there are some risks associated with Gamma Knife surgery. Other than mild nausea or headache related to the application and removal of the guilding device, there are usually no immediate side effects of Gamma Knife treatment. Possible delayed (three to 18 months after treatment) transient or persistent side effects depend on the size and location of the tumor or AVM and include problems such as weakness, numbness, hearing loss, imbalance or worsening of vision.