Assessing Short and Medium-Term Fluctuations of EEG Spectral Content in Minimally Conscious State Patients

The Minimally Conscious State (MCS) is a clinical condition within the spectrum of Disorders of Consciousness (DoC) whose hallmark feature is an inconsistently and fluctuating awareness. As such, this fluctuation in the clinical status complicates diagnostic assessment and contributes to the 40% of misdiagnosis. Quantitative measures extracted from electroencephalography (EEG) have been studied to address the issue of misdiagnosis. Single time-point analyses are, however, unable to account for the behavioral variability of the MCS condition and thus, there is the need for the identification of EEG-based features capable of capturing this variability. A cohort of 19 patients diagnosed with MCS and 22 healthy subjects was administered with a monitoring protocol in two consecutive days with the aim of describing the profile of variability over time of spectral EEG oscillations and compare it with the physiological variability. The variability of relative powers in delta, theta, and alpha bands was investigated over two temporal scales: minutes and hours. The entity of the fluctuations in EEG spectral content were compared between the two groups to distinguish between physiological variability and the variability in the EEG content possibly due to behavioral fluctuations inherent to MCS condition. Results indicated that MCS patients showed higher both short- and medium-term fluctuations in alpha relative power with respect to healthy individuals opening the possibility to identify the presence of fluctuations in awareness typical of MCS.