Bispectral analysis of electroencephalogram signals during recovery from coma: preliminary findings

The aim of this study was to investigate the accuracy of bispectral index (BIS), spectral edge frequency (SEF 95%), total power (TOTPOW) and frontal spontaneous electromyography (F-EMG) in monitoring consciousness in severely brain damaged patients. In 29 patients a total of 106 sedation-free and good quality EEG epochs were correlated with the level of consciousness as assessed by means of the Glasgow Liège Scale (GLS) and the Wessex Head Injury Matrix (WHIM). The strongest correlation with behavioural measures of consciousness was observed with BIS recordings. An empirically defined BIS cut-off value of 50 differentiated unconscious patients (coma or vegetative state) from conscious patients (minimally conscious state or emergence from minimally conscious state) with a sensitivity of 75% and specificity of 75%. These preliminary findings are encouraging in the search for electrophysiological correlates of consciousness in severe acute brain damage.