WELL & INFORMED ''Well & Informed'' is a weekly feature by health care professionals of TriHealth, a community partnership of Bethesda and Good Samaritan Hospital. Information for today's column was provided by Dr. Jamal M. Taha, neurosurgeon with the Mayfield Clinic.

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Q: What is a trigeminal neuralgia? How is it treated?

A: Trigeminal neuralgia, also called tic douloureux, is a nerve disorder that causes severe, stabbing facial pain. The pain lasts only a few seconds but can occur up to 50 times a day. Simple activities like chewing, smiling, or brushing teeth can trigger an attack. Even a cold breeze on the face can start a painful episode. The condition can last for several days or weeks, but can be followed by a remission for months or years. The frequency increases over time and may become disabling.

Pain occurs because of injury or damage to the trigeminal nerve, which supplies feeling to the face. It typically affects one side of the face, usually along the lower jaw and cheek or around the eye and forehead. Many people think their teeth are causing the pain, and some have them pulled unnecessarily.

Trigeminal neuralgia most often develops in people age 50 and older. The cause is often unknown, although sometimes a blood vessel in the brain can pulse against the nerve and, over time, cause a ''short circuit.'' Tumors, aneurysms (bulges in blood vessels) and multiple sclerosis also can cause injury to the nerve.

There is no cure for trigeminal neuralgia, but doctors can offer several effective treatments. The drug carbamazepine, originally developed to prevent seizures, can prevent painful attacks for about 98 percent of patients. After several years, its effectiveness may decrease and the individual will need further treatment. Some people cannot take carbamazepine. The doctor may prescribe another medication or treatment if the carbamazepine is not effective.

One option is major brain surgery called microvascular decompression. A neurosurgeon operates on the back of the head to locate the blood vessel that is banging against the trigeminal nerve. The surgeon separates the nerve and blood vessel, and places a cushion between the two. The procedure provides long-term, immediate pain relief.

Needle procedures destroy part of the nerve causing the pain without destroying the entire nerve. A neurosurgeon can use a needle with radiofrequency heating current, a needle to inject the chemical glycerol, or a needle with a small balloon attached that can be inflated to press against the nerve and destroy it. These needle procedures carry less risk than microvascular decompression. They trade pain for numbness, however. The radiofrequency technique is the most precise and long-lasting of these procedures.

A new option for treatment is available through a joint effort of Cincinnati's Mayfield Clinic and the Cleveland Clinic. Housed at the Cleveland Clinic, a machine called a gamma knife can precisely direct beams of radiation to the problematic portion of the trigeminal nerve and destroy it. Short-term results have been promising for this non-surgical procedure. Physicians are still awaiting long-term results.

For information about a support group for trigeminal neuralgia, call the Mayfield Clinic at 569-5290.