1.3 Resting EEG shows a severe background disorganization
During week 2, a comprehensive neurophysiological battery including visual and spectral analysis of spontaneous EEG (Figure 3) was performed to complement the behavioral evaluation. The visual analysis of clinical standard EEG demonstrated a diffuse slowing of the background activity with high-amplitude frontally-dominant slow-waves (>75µV) and sporadic lateralized epileptiform discharges on the left parietal sites, without a reproducible reactivity to exogenous stimuli (Figure 3, upper left panel). In accordance with recent review and specific recommendations (Curley et al. , 2022), these findings were interpreted as a severely abnormal EEG, a pattern more often found in VS/UWS patients and not suggestive of covert consciousness (Forgacset al. , 2014; Curley et al. , 2018). The severity of EEG slowing was confirmed by the quantification of Delta-Alpha Ratio (DAR) spectral power (Leon-Carrion et al. , 2008; Bai et al. , 2021; Wutzl et al. , 2021) showing values above the 95th percentiles of the distribution previously obtained in a reference population of 40 patients with a minimally conscious state (MCS) (Figure 3, upper right panel).