Gamma-knife radio surgery. The words may sound foreign, and a bit scary, especially when you realize that gamma-knife surgery is performed on the brain. But gamma-knife radio surgery can be a very effective way to treat brain tumors and other brain abnormalities, particularly those that can't be treated with traditional neurosurgery.

The gamma knife isn't actually a knife. Rather, it's a special machine that focuses high-intensity radiation into a small area. The radiation damages and destroys the unhealthy brain tissue. "The gamma knife is a cylindrical array of 201 sources of radiation aimed at one point," says Bruce Pollock, M.D., a neurosurgeon. "The individual radiation of each beam is low, but at the focal point of the gamma knife, a very high dose of radiation can be delivered."

This can be particularly useful for brain tumors located in areas of the brain that are hard to reach by means of conventional surgery. In addition to treating previously hard-to-reach areas, gamma-knife radio surgery has many other benefits. It typically requires only a mild sedative and local anesthesia, is relatively painless and, because no surgical incisions are made, has none of the postoperative complications — such as bleeding or infection — commonly associated with surgery.

 

 
Gamma-knife radiosurgery has proved effective in treating both cancerous (malignant) and no cancerous (benign) tumors that originate in the brain (primary brain tumors). It's also effective in treating tumors that develop in the brain as a result of cancer that has spread from another part of the body, called brain metastases. Gamma-knife radiosurgery is also useful in treating problems located deep within the brain, including:

	Arteriovenous malformations (AVMs). These are tangles of abnormal vessels that form between the arteries and veins in the brain. Over time, the veins or the AVMs may rupture and cause a brain hemorrhage.
	Dural arteriovenous fistulas (DAVFs). DAVFs are abnormal connections between arteries and veins in the scalp and skin covering your brain (dura matter) and a draining vein or sinus.
	Schwannomas. These are progressively enlarging, noncancerous (benign) tumors that originate from Schwann cells of the fatty insulation that covers nerve fibers (myelin sheath). Acoustic neuroma, a common type of schwannoma, is a tumor that develops in the internal auditory canal.
	Meningiomas. These are benign, slow-growing tumors that develop in the outer covering of the brain (meninges).
	Pituitary adenomas. These are benign tumors of the anterior pituitary gland.

Not all tumors and brain abnormalities can be suitably treated with the gamma knife. In general, people with lesions larger than 35 millimeters (mm) aren't good candidates for gamma-knife treatment.
Gamma-knife radiosurgery is also being used to treat other disorders, such as trigeminal neuralgia. Trigeminal neuralgia is a disorder that causes recurrent and sometimes extreme pain on one side of your face. In fact, a study published in the August 2002 issue of the Journal of Neurosurgery found that approximately 60 percent of patients with trigeminal neuralgia had some relief of facial pain following gamma-knife radiosurgery.
    

Gamma-knife radiosurgery involves four phases — headframe application, imaging, computerized dose planning and radiation delivery.

During the first phase, a special box-shaped frame, called a stereotactic headframe, is attached to your skull using specially designed screws. The headframe is used to help locate the area to be treated. Following local anesthesia, the headframe is secured with screws placed in the front and back of your head. The screws go through the skin to the outer part of your skull, so the headframe stays in place. The screws don't leave visible scars in most cases. You may feel pressure during the headframe placement. However, it's unlikely that you'll feel much pain. The frame is lightweight, so you'll be able to move your head after it's in place.

During the imaging phase, you'll undergo an MRI or CT scan, or — in the case of certain blood vessel malformations within the brain — cerebral angiography. These tests allow doctors to identify the precise area to be treated. These imaging studies, which give doctors a three-dimensional look at the area of concern within the brain, enhance the precision of gamma-knife procedures. Dr. Pollock says that when it's coupled with computer dose-planning software, the gamma knife has a working accuracy of within 1 mm or less.

During the computerized dose-planning phase, data collected during the imaging study are sent to a computer system so that the treatment team, including a neurosurgeon, a radiation oncologist and a medical physicist, can develop the plan for your procedure. This usually takes 1 to 2 hours, depending on the complexity of your problem.

After the individualized plan is completed, you are positioned on a couch to prepare for the radiation delivery. The total time for delivery usually ranges from 15 minutes to several hours. You won't feel the radiation, and very little noise accompanies the procedure. After the radiation has been delivered, you are taken to a recovery area, and you may be able to leave the hospital later that day.
 

PGamma-knife radiosurgery doesn't affect its target immediately. It may take weeks, months or even years before the full effects of the treatment become apparent. Your response to the surgery will be monitored by evaluating your symptoms and follow-up imaging studies.