Preserved somatosensory discrimination predicts consciousness recovery in unresponsive wakefulness syndrome

Abstract

Objective: To assess somatosensory discrimination and command following using a vibrotactile P300-based Brain-Computer Interface (BCI) in Unresponsive Wakefulness Syndrome (UWS), and investigate the predictive role of this cognitive process on the clinical outcomes.

Methods: Thirteen UWS patients and six healthy controls each participated in two experimental runs in which they were instructed to count vibrotactile stimuli delivered to the left or right wrist. A BCI determined each subject's task performance based on EEG measures. All of the patients were followed up six months after the BCI assessment, and correlations analysis between accuracy rates and clinical outcome were investigated.

Results: Four UWS patients demonstrated clear EEG-based indices of task following in one or both paradigms, which did not correlate with clinical factors. The efficacy of somatosensory discrimination strongly correlated (VT2: R = 0.89, p = 0.0000002, VT3: R = 0.81, p = 0.002) with the clinical outcome at 6-months. The BCI system also yielded the expected results with healthy controls.

Conclusions: Neurophysiological correlates of somatosensory discrimination can be detected in clinically unresponsive patients and are associated with recovery of behavioural responsiveness at six months.

Significance: Quantitative measurements of somatosensory discrimination may increase the diagnostic accuracy of persons with DOCs and provide useful prognostic information.

Keywords: Brain-computer interface; Disorders of consciousness; Minimal consciousness (MCS); P300; Somatosensory perception; Unresponsive wakefulness state (UWS).