The frequency of relapse and occurrence of intractable epilepsy following withdrawal of antiepileptic drug (AED) treatment in a Nova Scotia population-based cohort of children with epilepsy was studied at Dalhousie University, Halifax, NS, Canada. Patients (n=367), ages 1 month to 16 years, had partial or convulsive seizures, and at least 5 years follow-up. Those with benign rolandic epilepsy were excluded. Intractability was defined as one or more seizures every 3 months during the last year of follow-up despite maximum tolerated doses of 3 or more AEDs. Seventy one percent (260/367) had become seizure free for 1 to 4 years before discontinuing AEDs. Thirty percent had recurrence of seizures, but only 3 (1%) with recurrences developed intractable seizures. Two were eventually controlled, 1 after temporal lobectomy. Factors predictive of relapse were not determined. [1]

COMMENT. While one third have seizure recurrences, only 1% of children discontinuing treatment after 1 to 4 years of AED control will develop intractable epilepsy. The authors comment that their study group was evaluated before MRIs were available, and the advent of MR neuroimaging may have provided clues to predict cases at risk of epilepsy intractability.

The EEG and Risks of AED withdrawal. The EEG may be of value in predicting relapse during withdrawal of AEDs, according to a study of 128 patients (mean age 28 years) with partial epilepsies. (Ped Neur Briefs Aug 1996) [2]. Worsening of EEG abnormalities after starting drug withdrawal was more predictive of relapse than pre-withdrawal dysrhythmias or slowing. Several studies of the EEG and drug withdrawal have shown conflicting results regarding its value in predicting outcome (see Progress in Pediatric Neurology I and III, PNB Publishers, 1991 and 1997). Interictal EEG slowing was predictive of seizure recurrence in a prospective cohort study of 264 children (Ped Neur Briefs June 1994) [3]. Approximately one third relapsed during AED withdrawal, after 2 or more years of seizure control, a similar relapse rate to that reported in the current Camfield study.