Importance of Long-term EEG in Seizure-free Patients with Normal Routine EEG

Objective: Withdrawal of anti-seizure medicine (ASM) may be considered in epilepsy patients when seizure control is achieved. Predicting the risk of recurrence after discontinuing ASM. We compared routine electroencephalography (EEG) and long-term EEG (LTEEG) findings in seizure-free epilepsy patients with planned drug discontinuation. Hence, we aimed to emphasize the relationship between interictal electrophysiological findings and clinical features to assess the superiority of LTEEG over routine EEG in medication termination. Methods: Fifty-eight patients diagnosed with epilepsy and under the follow-up epilepsy outpatient clinics of our tertiary center with normal EEG and at least a two-year seizure-free period were included. LTEEG was performed in all these patients. Age, sex, seizure onset age, type and frequency, risk factors for epilepsy, anti-seizure medications, neurological examination, and electrophysiological and magnetic resonance imaging (MRI) findings were retrospectively recorded. Results: The study group consisted of 36 females (62.1%) and 22 males (37.9%). Their mean age was 38.67 (21-70) years. The mean duration of seizure freedom was 4.8 years. Neurological examination was abnormal in 9 patients, and MRI detected an anomaly in 22 patients (37.9%). Epileptiform anomalies on LTEEG were observed in 27 (46.6%) of 58 patients. LTEEG anomalies and seizure frequency were correlated with a statistically significant relationship. Conclusion: LTEEG may reveal interictal epileptiform anomalies even in patients with long-term seizure-free epilepsy with a normal routine EEG. On the basis of our results, we would like to emphasize the value of LTEEG to reevaluate a better treatment strategy in seizure-free patients.