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 (CRS-R), 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 76 days) 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 PCI) 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 while minimising motor artefacts, is a promising bedside tool. These are internal cross-validated estimates from a single-centre pilot cohort; external validation is required.