The characteristics and related influencing factors of ambulatory EEGs in patients seizure-free for 3-5 years.

OBJECTIVE: Epileptic patients have a higher relapse risk when EEGs before the initiation of anti-epileptic drug (AED) withdrawal show epileptiform activity. The purpose of this study is to assess the characteristics of ambulatory EEGs before the decision to withdraw AEDs and to clarify potential influencing factors for abnormal EEGs. METHODS: 214 epileptic patients were included in the study. These patients were seizure-free for 3-5 years on AED medication. Ambulatory 24-h EEGs were performed before the decision to withdraw AEDs. The demographical data and clinical information of the patients were used for the analysis of influencing factors for EEG findings. RESULTS: Ambulatory EEGs showed abnormalities in 41.1% of the patients (88/214). Of 88 patients with abnormal EEGs, 43 had unequivocal epileptic discharges; and 45 only had nonspecific EEG abnormalities. In our analysis, the potential factors for abnormal EEGs included female, delayed therapy, longer duration of intractability/treatment response time and medications failed. CONCLUSIONS: In many patients ambulatory EEGs remain abnormal even after seizure-free for 3-5 years; and many factors influenced the characteristics of the EEGs. The findings can assist in establishment of therapeutic principles.