Recurrence rate of seizure following discontinuation of anti-epileptic drugs in patients with normal long term electroencephalography

BACKGROUND: The usefulness of electroencephalography (EEG) in predicting seizure recurrence after antiepileptic drugs (AED) tapering is a controversial subject. There have been no studies which tested the additional yield of long-term over routine EEG recordings in predicting seizure recurrence after AED withdrawal. OBJECTIVE: The primary objective of our study is to determine the recurrence rate of seizure following AED withdrawal in patients with focal epilepsy, unknown cause who had normal long-term electroencephalography (LTEEG) and secondary objective is to analyze the variables that would predict seizure recurrence. MATERIALS AND METHODS: This was a prospective observational study. A total of 91 patients were included. 62 patients who had normal routine and LTEEG entered the final phase of the study were followed-up regularly for 1 year or until seizure recurrence whichever was earlier. RESULTS: A total number of 91 patients were enrolled for the first phase of the study. Of these, 13 (14.29%) patients had an abnormal routine EEG. Of the remaining patients, another 16 (17.58%) had abnormal LTEEG. The remaining 62 patients with normal routine and long-term EEG entered the final phase of the study. Of these, 17 patients (27.41%) had seizure recurrence during the follow-up while 45 (72.58%) remained seizure free until the end of the 1 year follow-up. The significant variables associated with a higher risk of seizure relapse were a positive past history of seizure recurrence on prior drug withdrawal (relative risk: 2.19, confidence interval: 1.01-4.74, P < 0.05) and the duration of epilepsy until seizure control was achieved (P < 0.009). CONCLUSIONS: The recurrence rate of seizure in patients with a normal LTEEG is 27.41%. A positive past history of seizure recurrence and a longer time to achieve seizure freedom with AED increased the risk of seizure recurrence.