Trigeminal neuralgia (TN) is paroxysmal (short & frequent) triggered face pain. Most patients respond very well to radiosurgery with the Gamma Knife, which is one of the best standard treatments for this condition.
Trigeminal neuralgia is characterized by sudden bursts (paroxysms) of face pain. These bursts are often triggered by a light touch around the mouth or face or by talking, eating, or brushing one's teeth. The pain sometimes gets worse or better for periods of weeks or months. The pain is in the areas supplied by the trigeminal nerve: the cheeks, jaw, teeth, gums, lips and less often around the eye or forehead. Usually pain occurs on just one side of the face, but in five to ten percent of patients, pain occurs on both sides of the face, although not at the same time. The pain responds to Tegretol (carbamazepine is the generic name), but sometimes the dose has to be increased and unpleasant side effects can occur.
Atypical features may coexist with some of the previously described symptoms. These atypical features may include a constant pain that is not always triggered by light touch. Patients with constant pain and TN are sometimes diagnosed as having atypical trigeminal neuralgia. Gamma Knife radiosurgery and other treatments for TN usually relieve the sharp electric-like pains that are triggered by light touch, but are less likely to relieve the constant, untriggered pains.
Incidence and Prevalence
Approximately 14,000 people develop TN each year in the United States; about 140,000 people have the condition. Trigeminal neuralgia is more common in patients with multiple sclerosis.
The cause of trigeminal neuralgia is not always certain. Approximately five percent of patients have a tumor pressing on the trigeminal nerve where it leaves the brain, while other patients have a blood vessel that presses on the trigeminal nerve, close to the brain. In some patients the cause cannot be determined.
Approximately five percent of patients with trigeminal neuralgia have multiple sclerosis. Patients with TN and multiple sclerosis are generally younger, and tend to first experience TN symptoms while in their mid 40s. These patients are more likely to have pain on both sides of the face (bilateral trigeminal neuralgia) and often have other neurological abnormalities, such as weakness or numbness in the arms or legs, dizziness, unsteadiness and double vision. Most patients in their 40s and 50s who have trigeminal neuralgia do not have multiple sclerosis. Patients who have TN but not multiple sclerosis tend to first experience TN symptoms while in their mid 50s.
In addition to a thorough history and physical examination, magnetic resonance imaging (MRI) of the brain is recommended. This procedure helps identify a brain tumor in the rare cases in which it is present along with TN. It may also help to diagnose multiple sclerosis. Often when the MRI is performed, some contrast material is injected into the vein so that the appearance of a small tumor, blood vessel, or other structures in the brain can be enhanced and made easier to detect.
There are some patients who have very mild face pain that may subside and even disappear without treatment. For severe pain, medications, especially Tegretol, are often highly effective. Tegretol can cause many side effects including sleepiness, forgetfulness, confusion, drowsiness, dizziness and nausea. Tegretol can also cause more serious problems such as bone marrow suppression, which can lead to anemia or a decrease in the number of white blood cells. A low white blood cell count can predispose a patient to contracting an infection. Rarely, these problems are life threatening. Blood counts must be monitored in order to lessen the chance of these complications occurring. Tegretol can also harm many other parts of the body, so patients who take this medicine must be under careful medical supervision. Tegretol interacts with many medications, so patients must advise their doctor of all the medications they are taking. Elderly patients and those with multiple sclerosis are more likely to experience the side effects of Tegretol.
There are other medications that can be used either alone or in combination to control trigeminal neuralgia pain. These are usually less effective than Tegretol. They include Lioresal (baclofen), Dilantin (phenytoin), Klonopin (clonazepam), Neurontin (gabapentin), or Lamictal (lamotrigine). All of them, except baclofen, are also used to prevent seizures.
A surgical procedure is recommended for patients who continue to experience severe pain or side effects from medications. In the past, patients with TN did not consider neurosurgical options until the pain or medicines became unbearable, because surgical procedures carried higher risks. Now that surgery is safer, and especially with GKRS, which is not only highly effective but safer than any of the other procedures, patients no longer have to wait to be in agony in order to undergo neurosurgical intervention.
There are five important neurosurgical procedures. Each is effective, but not always, and occasionally has to be repeated. These procedures are: Gamma Knife radiosurgery (GKRS), radiofrequency electrocoagulation (RFE), glycerol injection (GLY), balloon microcompression (BMC), and microvascular decompression (MVD). All of these procedures treat the trigeminal nerve at around the same place, close to where it leaves the brain.
Gamma Knife radiosurgery is the most recent and least invasive neurosurgical treatment for trigeminal neuralgia. Of all the surgical procedures, it is least likely to cause complications and uncomfortable new facial sensations (dysesthesias).
What is Gamma Knife Radiosurgery?
Gamma Knife radiosurgery is a method for treating certain problems in the brain without making an incision. Two hundred-one beams of cobalt-60 radiation are focused precisely on a specific region in the brain. In the case of TN, the target area is the trigeminal nerve, just where it leaves the brain. The treatment does not require general anesthesia, and the patient stays in the hospital for less than five hours.
Who is a candidate for Gamma Knife Radiosurgery?
Any patient with trigeminal neuralgia who has pain or has difficulty with the medicines used to relieve the pain is an excellent candidate for GKRS. The patient's age or medical condition does not affect the decision to have GKRS. Even the elderly or medically infirm can undergo this treatment. Patients who are receiving anticoagulants for other medical conditions do not have to stop or reverse the anticoagulation therapy prior to GKRS. Those who have had previous procedures for TN may also undergo GKRS. Patients who are concerned about the possibility of numbness are particularly good candidates for GKRS, because the chance of postoperative numbness occurring is very small. Patients who poorly tolerate medicines given for sedation and relief of pain during a procedure are also very suitable for GKRS because these medications are not necessary.
What results can be expected from GKRS?
Excellent or good pain relief occurs in approximately 85 to 90 percent of patients. Onset of pain relief may occur one day to four months after the procedure. About half of patients will experience pain relief within four weeks. Recurrent pain occurs within three years in 10 percent of patients. Patients with TN and multiple sclerosis are less likely to respond to GKRS than those without multiple sclerosis, although they also may be helped by the procedure. Gamma Knife radiosurgery can be repeated, but not until at least four months after the original procedure.
What are the complications from GKRS?
Major complications have not been reported. Additional numbness in the face or new facial sensations occur in less than 10 percent of patients. There are theoretical possibilities of delayed complications such as brain damage or brain tumor formation, but these are rare and have not been reported to occur in any patients treated for trigeminal neuralgia.
Gamma Knife radiosurgery was first performed in Sweden in the 1950s, but few patients were treated for TN. The Gamma Knife has been used in the United States since 1987, and most cases of TN have been treated during the past five years. Although there is not much information on long term effects, initial and medium range follow-up suggest that GKRS is not only effective but also very safe.
Linear Accelerator Radiosurgery
There is another form of radiosurgery, called LINAC (Linear Accelerator) radiosurgery. It uses high-energy X-rays delivered by a sequence of arcs, and is very different from GKRS. Only a few cases of TN have been treated with LINAC radiosurgery, and there are no reports on these cases in peer-reviewed journals. Unlike GKRS, LINAC radiosurgery has not been demonstrated to be an effective and safe treatment for trigeminal neuralgia.
Radiofrequency Electrocoagulation, Glycerol Injection and Balloon Microcompression
These procedures are performed through a needle that is inserted into the face and directed, under X-ray guidance, toward the trigeminal nerve. All of these procedures partially damagee facial numbness, which is sometimes very painful. Major complications, such as bleeding or infection in the brain, are rare but can be devastating when they occur.
Microvascular decompression is a major neurosurgical procedure in which the skull is opened. During the operation, which requires general anesthesia, the surgeon sees the nerve. If he or she finds a blood vessel pressing on the trigeminal nerve, a soft piece of material will be placed between the blood vessel and the nerve, thus lifting the blood vessel away from the nerve. This operation carries greater risks than the other procedures do, and these risks, although infrequent, include possible death, stroke, bleeding, infection, inflammation of the surface of the brain, facial weakness, hearing loss, facial numbness and pain.
Gamma Knife radiosurgery is a major advance in the treatment of trigeminal neuralgia, an otherwise agonizing condition characterized by paroxysmal triggered face pain. Gamma Knife radiosurgery not only relieves the pain as well as the other neurosurgical forms of treatment, but it does so with fewer complications.
The Gamma Knife is the only radiosurgical machine for which positive results of trigeminal neuralgia treatment have been published in peer-reviewed journals.