Gamma Knife radiosurgery is a type of radiation therapy used to treat tumors and other abnormalities in the brain.
In Gamma Knife radiosurgery, specialized equipment focuses close to 200 tiny beams of radiation on a tumor or other target. Although each beam has very little effect on the brain tissue it passes through, a strong dose of radiation is delivered to the site where all the beams meet.
The precision of Gamma Knife radiosurgery results in minimal damage to healthy tissues surrounding the target. In some cases, Gamma Knife radiosurgery may have a lower risk of side effects compared with other types of radiation therapy. Also, Gamma Knife radiosurgery is often a safer option than is traditional brain surgery.
Gamma Knife radiosurgery is usually a one-time therapy completed in a single day.
Where Uses Gamma Knife?
Gamma Knife radiosurgery is often an appropriate alternative to standard brain surgery (neurosurgery), which requires incisions in the skull, membranes surrounding the brain and brain tissue. This type of radiation treatment is usually performed when:
Gamma Knife radiosurgery is most commonly used to treat the following conditions:
Brain tumor. Radiosurgery is useful in the management of small noncancerous (benign) and cancerous (malignant) brain tumors.
Radiosurgery damages the genetic material (DNA) in the tumor's cells. The cells lose their ability to reproduce and may die, and the tumor may gradually shrink.
Arteriovenous malformation (AVM). AVMs are abnormal tangles of arteries and veins in your brain. In an AVM, blood flows from your arteries to veins, bypassing smaller blood vessels (capillaries). AVMs may disrupt the normal flow of blood and lead to bleeding.
Radiosurgery destroys the AVM and causes the blood vessels to close off over time.
Trigeminal neuralgia. Trigeminal neuralgia is a disorder of one or both of the trigeminal nerves, which relay sensory information between your brain and areas of your forehead, cheek and lower jaw. This nerve disorder causes disabling facial pain that feels like an electric shock.
After treatment, many people will experience pain relief within a few days to a few months.
Acoustic neuroma. An acoustic neuroma (vestibular schwannoma), is a noncancerous (benign) tumor that develops along the main balance and hearing nerve leading from your inner ear to your brain.
When the tumor puts pressure on the nerve, a person can experience hearing loss, dizziness, loss of balance and ringing in the ear (tinnitus). As the tumor grows, it can also put pressure on the nerves affecting sensations and muscle movement in the face.
Radiosurgery may stop the growth or minimize the size of an acoustic neuroma with little risk of permanent nerve damage.
Pituitary tumors. Tumors of the bean-sized gland at the base of the brain (pituitary gland), can cause a variety of problems. The pituitary gland controls hormones in your body that control various functions, such as your stress response, metabolism and sexual function.
Radiosurgery can be used to shrink the tumor and lessen the disruption of pituitary hormone regulation.
What Are Risks?
Gamma Knife radiosurgery doesn't involve surgical incisions, so it's generally less risky than traditional neurosurgery. In traditional neurosurgery, you may have risks of complications with anesthesia, bleeding and infection.
Early complications or side effects are usually temporary. They may include:
Fatigue. Tiredness and fatigue may occur for the first few weeks after Gamma Knife radiosurgery.
Swelling. Swelling in the brain at or near the treatment site can cause symptoms such as headache, nausea and vomiting. Your doctor may prescribe anti-inflammatory medications (corticosteroid medications) to prevent such problems or to treat symptoms if they appear.
Scalp and hair problems. Your scalp may be red, irritated or sensitive at sites where a device is attached to your head during the treatment. Some people temporarily lose a small amount of hair.
Rarely, people may experience late side effects, such as other brain or neurological problems, months after Gamma Knife radiosurgery.
How To Prepare Before Application?
Don't eat or drink anything after midnight the night before the procedure.
Talk to your doctor about whether you can take your regular medications the night before or morning of the procedure.
Avoid wearing the following items during the procedure:
Tell your doctor if you:
What You Can Expect?
Gamma Knife radiosurgery is usually an outpatient procedure, but the entire process will take most of a day. You may be advised to have a family member or friend who can be with you during the day and who can take you home. In some cases, an overnight stay in the hospital may be necessary.
You'll have an intravenous (IV) line, a tube that delivers fluids to your bloodstream to keep you hydrated during the day. A needle at the end of the IV is placed in a vein, most likely in your arm.
Before the procedure
Before the procedure begins, you'll have a lightweight frame attached to your head with four pins. This frame will stabilize your head during the radiation treatment and serve as a point of reference for focusing the beams of radiation. During this process:
Tumors. Imaging for tumors may include computerized tomography (CT scan) or magnetic resonance imaging (MRI). In a CT scan, a series of X-rays create a detailed image of your brain. In an MRI scan, a magnetic field and radio waves create detailed images of your brain.
Doctors may inject a dye into a blood vessel to view the blood vessels in your brain and highlight blood circulation. In some cases, you may have an MRI and CT scan.
Arteriovenous malformations (AVMs). Imaging for brain AVMs may include CT scans, MRI scans, cerebral angiograms or some combination of these tests.
In a cerebral angiogram, a doctor inserts a small tube in a blood vessel in your groin and threads it to the brain using X-ray imaging. A doctor injects dye through the blood vessels to make them visible on X-rays. Your doctor may inject a dye into a blood vessel during CT or MRI scans to view the blood vessels and highlight blood circulation.
Trigeminal neuralgia. An MRI or CT scan is used to create images of nerve fibers to select a target area for treating trigeminal neuralgia.
The results of the brain scans are fed into a computerized planning system that enables the radiosurgery team to plan the appropriate areas to treat, dosages of radiation and how to focus the radiation beams to treat the areas. This planning process may take an hour or two. During that time, you can relax in another room, but the frame must remain attached to your head.
Children are often anesthetized for the imaging tests and during the radiosurgery. Adults are usually awake, but you may be given a mild sedative to help you relax.
During the procedure
You'll lie on a bed that slides into the Gamma Knife machine, and your head frame will be attached securely to a helmet inside the machine. The procedure may take less than an hour to about four hours, depending on the size and shape of the target. During the procedure:
After the procedure, you can expect the following:
How Are Results?
The treatment effect of Gamma Knife radiosurgery occurs gradually, depending on the condition being treated:
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