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.