Anti-epileptic medications are the mainstay of treatment for epilepsy, but even the newest, most advanced drugs don't work for everyone. In fact, 30 percent to 40 percent of people with epilepsy continue to have seizures while they are taking anti-seizure drugs.

The most common form of epilepsy involves seizures that begin in the brain's temporal lobes, the sections along the sides of your brain. This type of epilepsy is the hardest to control with medication, but it is the type most likely to respond to surgical treatment.

Once considered to be only a last resort, epilepsy surgery has become increasingly common, even for children. Improvements in imaging technology now make it easier for doctors to more precisely locate the section of brain responsible for the seizures.

To be considered for surgery, you must have tried at least two anti-epilepsy drugs without success. If two drugs have failed, it is highly unlikely that any other anti-epilepsy drug will help you.

People whose seizures always start in the same area in the brain benefit most from surgery for epilepsy. Surgery is rarely considered for people whose seizures start in several areas of the brain.

Another requirement is that your seizures must be interfering with your quality of life. Even a single seizure a month can impair your academic or job performance, keep you from driving and limit your employment opportunities. On the other hand, some people have such mild seizures that the risks of the surgery outweigh the benefits.

Because some childhood seizures stop at puberty, doctors often hesitate to recommend surgery for children. However, a child's chance of outgrowing the seizure disorder has to be weighed against the risk of brain damage from recurrent seizures and the burden of long-term treatment with anti-epilepsy drugs.

In fact, children may have the most to gain from epilepsy surgery because they risk the greatest harm from epileptic seizures. Because their brains are still developing, children are more vulnerable to permanent brain damage related to epilepsy. Seizures also interfere with children's social development.

Any type of surgery, particularly brain surgery, carries risks. Epilepsy surgery typically removes a portion of the brain measuring 3 to 5 cm, roughly the size of a golf ball. After the surgery, you may have memory or language problems, but these are usually temporary. Life-threatening complications, such as stroke or brain hemorrhage, occur in only 1 percent to 2 percent of cases.

But repeated epileptic seizures carry their own risks.

"Patients face risks whether they have the surgery or not," says Gregory Cascino, M.D., chairman of the epilepsy division at Mayo Clinic, Rochester, Minn.

"These people can't attain their education or employment goals," Dr. Cascino says. "Then there's the risk of physical trauma, from falls or getting burned during seizures. Prolonged seizures can injure the brain. Epilepsy can even cause sudden death."

Advances in imaging technology now make it much easier to locate exactly where seizures originate. Your evaluation may include:

Baseline EEG (electroencephalogram). A test in which electrodes are placed on the scalp to measure electrical activity produced by the brain.

Video EEG. After being admitted to a hospital room, your seizures will be recorded on continuous EEG with video monitoring. Your seizure medications will be reduced or temporarily stopped, allowing your doctor to obtain recordings of several seizures. Correlating the changes in your EEG with your body's movements during a seizure helps pinpoint the area of your brain in which your seizures are starting.

MRI of the head. This imaging study can identify abnormal lesions or scar tissue in the brain that could be causing seizures.

SPECT (single photon emission computed tomography). A radioactive substance is injected into the bloodstream, after which the brain is scanned. The scan image varies in color depending on the amount of blood flow. Typically, blood flow is higher in the part of the brain where seizures originate. SPECT scans can be taken during or between seizures. In some cases, doctors combine several types of imaging techniques to help locate the troublesome area of the brain.

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Pinpointing seizure location In this example, SPECT scans taken during and between seizures are ... << ENLARGE

You usually will be asleep during the surgery, which takes about five or six hours to complete. At least a portion of your head will be shaved. An incision will be made in your scalp and a piece of bone next to the brain will be removed.

During the surgery, electrical recordings will be made from the surface of the brain and from within the brain. This helps the neurosurgeon locate and remove the areas of your brain that cause seizures.

After the bone is replaced and your scalp is sutured closed, you will spend a few hours in the recovery room and then be transferred to the intensive care unit for a day or two. You should be home from the hospital within a week. Most people are able to return to work or school two or three months after surgery.

In general, the results of epilepsy surgery depend on the region of the brain causing the seizures. The best results can be expected when seizures arise from the temporal lobes, located along the sides of your head.

Currently, 60 percent to 80 percent of patients who undergo temporal lobe surgery are seizure-free after surgery. Another 10 percent to 20 percent have significantly fewer seizures. Some people, however, see no change in their seizure pattern after surgery.

You also must continue to take anti-epileptic drugs after surgery, although the doses are usually lower than those needed before surgery. A few years after surgery, it may be possible to discontinue the medication.

"Medicine is continued to avoid the occurrence of any severe or life-threatening seizure activity," Dr. Cascino says. "The issue of continued medication is not a big deal to patients. They are more focused on becoming seizure-free."