The frequency of seizure recurrence and outcome factors associated with antiepileptic drug (AED) withdrawal following successful epilepsy surgery were evaluated retrospectively in 210 patients treated between 1989 and 1993 at the Mayo Clinic, Rochester, MN. The mean age was 32 years; 6 were children younger than 12 years, and 19 were adolescents (12-18 years). Ninety percent had a temporal lobe resection and in 10% resection was extratemporal. Medical therapy was reduced in 96 and discontinued in 84 patients. At 2 and 5 year follow up, seizure recurrence rate after complete AED withdrawal was 14% and 36%, in contrast to only 3% and 7% of 30 patients who continued AEDs unchanged. Seizure-free patients who partially reduced AEDs had an intermediate rate of recurrence between that of controls and those with complete AED withdrawal. After AED withdrawal, prevalence of seizure recurrence was higher in patients with normal preoperative MRI studies (40%) compared to those with focal pathology (20%), including hippocampal atrophy (NS). Factors not predictive of seizure recurrence after AED withdrawal included electrocorticography at operation, extent of resection, EEG postoperatively, and seizure-free duration after surgery. 
COMMENT. Long-term seizure recurrence rate following AED withdrawal in patients, principally adults, successfully treated with surgery may be as high as 36% with complete AED withdrawal, compared to 14% following partial AED withdrawal, and 7% when AED therapy is unchanged. A normal preoperative MRI is a risk factor for higher seizure recurrence than in patients with well defined pathology. When seizures recur after AED withdrawal, renewal of therapy is usually successful, irrespective of the seizure-free duration after surgery. The results of this study are inconclusive regarding a general policy for AED withdrawal after successful epilepsy surgery, and should not be applied to children who formed only 12% of the study group. Each patient must be considered as an individual when evaluating the pros and cons of AED therapy.