F11. Scalp EEG recording of direct current shifts during generalized spike-and-wave complexes in adult idiopathic generalized epilepsy

Introduction Direct current (DC) shifts are EEG components slower than delta waves. In focal epilepsy, ictal DC shifts recorded with intracranial and scalp electrodes have been reported to be helpful to delineate epileptogenic zone. Here we investigated DC shifts during generalized spike-and-wave complexes (SWC) in adult patients with idiopathic generalized epilepsy (IGE). Methods Nine patients with electro-clinical diagnosis of IGE (four males), age 35 ± 13 years (mean ± SD), were included. Conventional scalp EEG was recorded for around 30 min, using Ag/AgCl electrodes set according to international 10–20 system, with sampling frequency of 500 Hz. In total, 55 EEG records for 1836 min (mean 6.9 records per patient) were analyzed. All records were reviewed offline under the condition of TC 0.3 s, 30 mm/s, and HF 60, in various montages, all SWC were marked, and segments with significant artifacts were excluded by visual inspection. Then the reviewing condition was changed into the average reference montage excluding frontopolar and earlobe electrodes, TC 2.0 s, 60 s/page, and HF15. Baselines of each EEG waveform were set referring to the segment from 20 s to 10 s before the SWC onset. DC shifts were defined as sustained negative and/or positive slow potentials with the amplitude higher than 20  μ V, better delineated with TC 2.0 s than 0.3 s, and reproducible in location within each patient. Results Among 272 SWC, 175 eligible SWC were analyzed (duration 1.5 ± 1.6 s, amplitude 9.1 ± 17.1  μ V), and DC shifts were present at 30 times (17.1% of SWC analyzed, amplitude 29.7 ± 20.2  μ V). DC shifts were mainly observed in fontal and frontopolar electrodes. SWC with DC shifts showed significantly longer duration than those without (2.9 ± 3.1 s v.s. 1.2 ± 0.7 s, p = 0.008). Amplitude and duration of DC shifts showed significant positive linear correlation (r = 0.60, p  Conclusion Scalp-recorded DC shifts during SWC was associated with persistent EEG seizures in adult patients with IGE. More confined distribution of DC shifts than that of SWC may reflect heterogeneous epileptogenicity within each IGE patient.