Twenty percent of people with epilepsy develop drug-resistant seizures

Twenty percent of people with epilepsy will eventually develop seizures that are resistant to medication, even if they have experienced long periods with no seizures at all, according to a study led by a Yale researcher.

The large multi-center trial included 333 persons who sought surgery at six medical centers in the Northeast and one in the Midwest because their seizures could no longer be controlled by medication, said Susan Spencer, M.D., a professor of neurology at Yale School of Medicine.

We did very detailed histories to see when their seizures began and when they failed their first and second drug treatment and how long it took to get to that point,” said Spencer, senior author of the study published in the current issue of the journal, Neurology.

More than 25 percent of the patients had had a long period of complete seizure control. Some even went off their medication. Nearly 10 percent of these patients had no seizures for an interval of five years. A significant number, Spencer said, also had more than one seizure-free interval.

We don't know what predicts this group,” she said, “although the people who were younger at the time of their first seizure were the most likely to become controlled for some interval of time.”

Spencer said one purpose of the research is to try to predict from the onset of the first seizure which patients will eventually become resistant to medication and which ones will be able to control their seizures with medication.

There has been increasing inclination when surgery might be appropriate treatment to do it earlier and earlier,” she said. The definition adopted by many medical centers on when surgery for epilepsy is appropriate is when a person has become resistant to a second medication for their seizures.

The researchers said in the study that much remains unknown about the natural history of intractable epilepsy, including how long it typically takes before intractability becomes evident. The new data, they said, could guide the design of future studies, resolve certain discrepancies in the literature, and provide more accurate information about long-term prognosis.

The possibility that an early benign course does not necessarily ensure a good long-term outcome is sobering news,” Spencer said. “However, if it is true, then we may also be able to learn to identify early those patients who will later develop intractable temporal lobe epilepsy regardless of a relatively benign initial course. This raises the possibility of identifying the mechanisms involved in this progression and could eventually open the door to therapeutic approaches that might prevent some forms of epilepsy from becoming intractable.”

Other centers participating in the study are Northern Illinois University; University of Rochester School of Medicine; Albert Einstein College of Medicine; the University of California at Los Angeles; Thomas Jefferson University Medical School; Minnesota Comprehensive Epilepsy Program; Columbia University Medical School.

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