Purpose: Up to one-half of epilepsy surgery patients will have at least one seizure after surgery. We aim to characterize the prognosis following a first postoperative seizure, and provide criteria allowing early identification of recurrent refractory epilepsy.
Methods: Analyzing 915 epilepsy surgery patients operated on between 1990 and 2007, we studied 276 who had >or=1 seizure beyond the immediate postoperative period. The probability of subsequent seizures was calculated using survival analysis. Patients were divided into seizure-free (no seizures for >or=1 year) and refractory (persistent seizures) and analyzed using multivariate regression analysis.
Results: After a first seizure, 50% had a recurrence within 1 month and 77% within a year before the risk slowed down to additional 2-3% increments every two subsequent years. After a second seizure, 50% had a recurrence within 2 weeks, 78% within 2 months, and 83% within 6 months. Having both the first and second seizures within six postoperative months [odds ratio (OR) 4.04; 95% confidence interval (CI) 2.05-8.40; p = 0.0001], an unprovoked initial recurrence (OR 3.92; 95% CI 2.13-7.30; p < 0.0001), and ipsilateral spikes on a 6-months postoperative electroencephalography (EEG) (OR 2.05; 95% CI 1.10-3.88; p = 0.025) predicted a poorer outcome, with 95% of patients who had all three risk factors becoming refractory. All patients with cryptogenic epilepsy and recurrent seizures developed refractoriness.
Discussion: Seizures will recur in most patients who present with their first postoperative event, with one-third eventually regaining seizure-freedom. Etiology and early and unprovoked postoperative seizures with epileptiform activity on EEG at six postoperative months may predict recurrent medical refractoriness.