Significance of multiple neurophysiological measures in patients with chronic disorders of consciousness

Objective The aim of this study was to verify the value of multiple neurophysiological tests in classifying disorders of consciousness (DOCs) in patients in a chronic vegetative or minimal consciousness state categorised on the basis of the Coma Recovery Scale (CRS). Methods The study included 142 patients, all of whom underwent long (18 h) EEG-polygraphic recordings including one night. The EEG was scored using the Synek scale and sleep patterns using an arbitrary scale. Absolute total power and relative EEG power were evaluated in different frequency bands. Multimodal evoked potentials (EPs), including auditory event-related potentials, were also evaluated and scored. Results The most information came from the combined multimodal EPs and sleep EEG scores. A two-step cluster analysis based on the collected information allowed a satisfactory evaluation of DOC severity. Spectral EEG properties seemed to be significantly related to DOC classes and CRS scores, but did not seem to make any significant additional contribution to DOC classification. Conclusions Multiple electrophysiological evaluations based on EEG, sleep polygraphic recordings and multimodal EPs are helpful in assessing DOC severity and residual functioning in patients with chronic DOCs. Significance Simple electrophysiological measures that can be easily applied at patients’ bedsides can significantly contribute to the recognition of DOC severity in chronic patients surviving a severe brain injury.