T160. Magnetoencephalography findings of benign epileptiform transients of sleep on scalp EEG in three patients with temporal lobe epilepsy

Abstract

Introduction Benign epileptiform transients of sleep (BETS) is a finding on electroencephalography, defined as monophasic or diphasic transients with low amplitude ( μ V) and short duration ( Methods Patient 1, a 37-year-old right-handed male, was diagnosed with left TLE. Complex partial seizures started from age 15 years. Video-EEG (VEEG) showed interictal left anterior and posterior temporal sharp waves, and left temporal seizure onset was suggested. Magnetic resonance (MR) imaging revealed a mass lesion in the left lateral temporal lobe, suspected to be dysembryoplastic neuroepithelial tumor. Patient 2, a 38-year-old right-handed male, was diagnosed with left TLE. Complex partial seizures started from age 20 years. VEEG showed interictal bilateral independent temporal spikes, and left temporal seizure onset was suggested. MR imaging showed no abnormalities. Patient 3, a 33-year-old right-handed female, was diagnosed with right TLE. Complex partial seizures with oral automatism started from age 20 years. VEEG showed interictal right anterior temporal spikes, and right temporal seizure onset was suggested. MR imaging showed no abnormalities. All three patients underwent simultaneous EEG-MEG recording. EEG electrode placement used the 10–10 system with additional anterior temporal electrodes. MEG used a 200 channel whole-head system (MEGvision PQA160C, Ricoh Company, Ltd., Tokyo, Japan). The study investigated MEG activities correlated with EEG findings concordant with BETS. Results In Patient 1, MEG spikes correlated with BETS in the left temporal lobe had epileptic form, with high amplitude spike activity followed by slow wave activity. The source as evaluated with equivalent current dipoles was estimated around the left temporal lesion. In Patient 2, MEG spikes correlated with BETS in the right temporal lobe had epileptic form, with high amplitude spike activity followed by slow wave activity. No activity fulfilling the definition of BETS was detected in the left hemisphere. In Patient 3, no apparent MEG activity correlated with BETS was seen in the right temporal lobe. Conclusion The present study demonstrated variations in MEG findings correlated with EEG BETS in patients with TLE. These results may indicate heterogeneous background of BETS, so that only some BETS have an epileptic mechanism.