WASHINGTON, DC—Intractable epilepsy often does not become that way for a very long time, and the time to intractability varies according to type of epilepsy, Anne T. Berg, PhD, said at the 2005 Joint Annual Meeting of the American Epilepsy Society and the American Clinical Neurophysiology Society. Dr. Berg, who heads a major, NIH-funded, long-term study of epilepsy, reported nine-year follow-up data from a community-based study of 613 children with newly diagnosed epilepsy.

The study used two definitions for intractable epilepsy. The "strict" definition required two antiepileptic drug (AED) failures, at least one seizure per month for 18 months, and no seizure-free periods longer than three months during that time. The "loose" definition required two AED failures, Dr. Berg elaborated. She is Professor of Biological Sciences at Northern Illinois University in DeKalb.

"There is a general assumption that if epilepsy is going to be intractable, that intractability will be apparent essentially from the outset. Retrospective data and impressions based on surgical patients have suggested otherwise. In one study of adult surgical patients, largely with temporal lobectomies, we found that [the time] from the initial onset of epilepsy to the failure of their second drug had a median of nine years," Dr. Berg said. "In the literature, roughly two thirds of patients [who have surgery for intractable epilepsy in adulthood] started having epilepsy during childhood or early adolescence. Retrospective data suggest that with a median follow-up of nine years, roughly a third to half of the intractable cases that might occur in the cryptogenic/symptomatic partial epilepsy group have yet to declare themselves."

In this study, under the "strict" criteria, intractable epilepsy developed in 82 children. This included 13% of those with cryptogenic or symptomatic partial epilepsy, 52% of those with an epileptic encephalopathy, and 4% of those with idiopathic or other forms of epilepsy.

"Twenty-five—30%—of the 82 intractable cases took longer than three years to meet the strict criteria for intractability," Dr. Berg said. The time to development of intractable epilepsy varied significantly depending on type of epilepsy. In significantly more patients with cryptogenic or symptomatic partial epilepsy than in those with epileptic encephalopathy, the disease did not progress to intractability until after three or more years (45% versus 14%), she noted.

One hundred thirty-five children met the "loose" criteria for intractability. Thirty-two (24%) met the criteria more than three years after diagnosis. Again, those with cryptogenic or symptomatic partial epilepsy were more likely to have developed intractable disease only after three or more years (36% versus 2% of the epileptic encephalopathy group). Dr. Berg also said that for more than 70% of those in the cryptogenic or symptomatic partial epilepsy group for whom a second drug proved ineffective more than three years after diagnosis, a remission of at least one year had occurred before the second drug failure.

"In cryptogenic and symptomatic partial epilepsy, sometimes the expression of intractability can be quite delayed. Many of these people had previously been seizure-free and seemingly doing well. A very important question that we now have to consider is, If you follow someone day in, day out, on what day do you finally say, ‘OK, now this patient is really in trouble’? I don’t think we have a consensus on that," Dr. Berg said. "Also, if there are people who are doing well, but there are future risks before them, does this mean that there may be a potential period for early intervention when something could be done to prevent their epilepsy from becoming intractable?" she asked.

NR

—Janis Kelly

Suggested Reading
Berg AT. Defining intractable epilepsy. Adv Neurol. 2006;97:5-10.
Berg AT, Langfitt J, Shinnar S, et al. How long does it take for partial epilepsy to become intractable? Neurology. 2003;60:186-190.

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