Assessing consciousness by near-nerve electrostimulation in intensive rehabilitation

Objective.Consciousness diagnosis in prolonged disorders of consciousness (pDoC) relies on the Coma Recovery Scale-Revised, yet consciousness or its potential for recovery may escape behavioural detection. We tested whether near-nerve stimulation (NNS) of the median nerve, compared to standard surface cutaneous stimulation (SCS), could provide an EEG-based marker of consciousness and its recovery, by specifically eliciting sensory responses.Approach.Nineteen pDoC patients (median age 69 years, time post-onset 74 d) underwent NNS and SCS with high-density EEG. We quantified evoked potentials, global field power and perturbational complexity, and defined recovery as improvement in clinical diagnosis over 2 months.Main results.A combined NNS index (field-power peak and perturbational complexity index) classified chronic unresponsive patients with a leave-one-subject-out accuracy of 94.7% (95% CI 77.9%-99.4%), sensitivity 100% (95% CI 73.8%-100%) and specificity 90.9% (95% CI 64.7%-99.0%), outperforming SCS (accuracy 63.2%).Significance.These findings suggest that NNS, by selectively activating sensory pathways without intentional motor recruitment, is a promising bedside tool. These are internal cross-validated estimates from a single-centre pilot cohort; external validation is required.