Effect of a ketogenic diet on EEG: analysis of sample entropy.

Although ketogenic diet (KD) is an effective alternative therapy for controlling intractable seizures, the anticonvulsant mechanism still remains unclear. Sample entropy (SampEn) provides a generalized measure of regularity in time-series data. To investigate the potential anticonvulsive mechanism of a KD, we analyzed the SampEn of electroencephalography (EEG) data in patients with intractable pediatric epilepsy before and after treatment with a KD. Seventeen pediatric patients with epilepsy who were treated with KD were enrolled in present study. Patients were classified as good responder and poor responder according to therapeutic responsiveness on KD. Thirty segments of 30-s epochs were selected before and after KD from each patient which were subject to SampEn. The KD increased the SampEn in the whole patient population; the SampEn increased significantly in all electrodes in the good responders, but the change in SampEn varied according to the electrode in the poor responders. Before the KD, the good responders had significantly lower SampEn values than the poor responders, but after the KD, SampEn values were higher in the good responders than in the poor responders. KD may have an anticonvulsive effect by decreasing the regularity of the EEG dynamics.