The Gamma Knife is emerging as an attractive treatment option for people who suffer from trigeminal neuralgia.
Trigeminal neuralgia or tic doloureux is charterized by brief episodes of extremely intense facial pain often radiating down the jaw. These episodes can occur spontaneously or can be triggered by light touch, chewing, or changes in temperature (i.e. cold). The pain is so intense as to be completely disabling. In addition, weight loss is common because oral triggers prevent affected individuals from eating enough to maintain adequate nutrition. Trigeminal neuralgia is caused by irritation of the fifth cranial nerve (the trigeminal nerve) which is responsible for providing sensation to the face. This irritation is occassionally due to benign tumors or to multiple sclerosis either of which can usually be detected by a high quality MRI of the brain. In the majority of cases, however, imaging of the brain does not reveal a cause of the nerve irritation. In such cases a small vessel (usually an artery but occassionally a vein) is often found to be compressing the root entry zone of the trigeminal nerve at the
brainstem.
There are three main surgical options for treating trigeminal neuralgia when medications are unsuccessful. One is a major operation that repositions the artery that irritates the nerve as it comes out of the brain stem. This operation is known as microvascular decompression.
The second category of surgery are those operations that numb the nerve by heating, compressing, or chemically inactivating it. They can be done by inserting a needle into the skull through the face. Radiofrequency lesioning (RFL) is the most commonly performed of these procedures. All of them have the disadvantage of producing facial numbness. Both of these types of operations work immediately.
Gamma Knife radiosurgery, is the newest surgical treatment for trigeminal neuralgia. Gamma Knife offers a similarly high rate of pain control without surgery and in the vast majority of patients without producing significant numbness. Its potential disadvantages include the use of radiation and the fact that the benefit often takes 6 weeks or more to be considered successful.
Thus those patients with the most severe symptoms might choose microvascular decompression or radiofrequency lesioning. Many other patients and physicians find that Gamma Knife is the ideal treatment for their trigeminal neuralgia.
The 22-ton Gamma Knife unit aims
201 "pencil beams" of radioactive cobalt-60 at the target brain tissue, sharply focused to minimize radiation
effects to surrounding healthy brain tissues. In the case of trigeminal neuralgia the target is only four millimeters
in diameter. Using computers, a team of neurosurgeons, radiation oncologists and radiation physicists precisely
conform the radiation dose to the size and shape of the lesion.
