Brief antiepileptic drug withdrawal prolongs interval to next seizure

OBJECTIVE: To evaluate the course of seizure control after reinstitution of antiepileptic drugs (AEDs) in patients whose AEDs were discontinued during inpatient EEG-video monitoring. METHODS: The authors studied prospectively patients with intractable epilepsy admitted for EEG-video monitoring with AED withdrawal. They examined seizure diaries in the 2 months preceding admission and recorded the number of seizures during hospitalization and for 2 months after discharge. They also recorded the interval between the last two seizures preceding admission (S-S pre), from the last seizure to admission (S-A), from discharge to the first seizure after discharge (D-S), and between the first and the second seizures following discharge (S-S post). RESULTS: Sixty patients qualified for the study. There was a significant decrease in seizure frequency in the 2 months after discharge compared with baseline (p = 0.02). For patients who had at least two seizures during follow-up, the mean D-S interval was significantly longer than mean S-S pre and S-S post (p < 0.005), whereas the latter two intervals were comparable. Prolongation of D-S was related to duration off AEDs and to the AED restarted, but not to the number or severity of seizures during monitoring. CONCLUSION: Seizure improvement after reinstitution of antiepileptic drugs (AEDs) is due primarily to prolongation of the interval from reinstitution of AEDs to the next seizure. This may reflect increased patient responsiveness to AED therapy after a drug "holiday" and has implications for experimental AED testing in the setting of presurgical evaluation.