The natural history of drug resistant epilepsy: epidemiologic considerations.

Approximately 160,000 United States residents will be evaluated for newly identified unproved seizures in 1990. While the majority will have a favorable prognosis and more than 50% will ultimately be able to discontinue medication, about 10,000 will fall into the category 'intractable'. There are well established predictors for seizure remission and for successful withdrawal of medications, including seizure type, etiology, age at onset, neurologic status, and family history. There are few studies which have evaluated predictors for poor outcome, in part because of difficulties with definition. Predictors of poor outcome are not necessarily the converse of predictors of good outcome. Identification of such factors is important to allow earlier referral of patients destined to meet criteria for intractable to allow alternative therapies to be instituted.