Assessment of mismatch negativity and P300 response in patients with disorders of consciousness

OBJECTIVE: To evaluate changes in mismatch negativity (MMN) and P300 response in vegetative state (VS) and minimally conscious state (MCS) patients before and after treatment, and their value for prediction of prognosis. PATIENTS AND METHODS: Event-related potentials (ERPs), performed on 11 patients classified as VS (n = 6) or MCS (n = 5), and five healthy participants (i.e., control group). We performed a six months telephone follow-up to monitor changes in consciousness recovery. RESULTS: Comparison of the three groups showed significantly higher MMN latency elicited by salient stimuli and P300 elicited by the subject's own name for the VS group, as well as significant difference in amplitudes of MMN elicited by frequent stimuli and P300 elicited by other first names for this group. The source of MMN and P300 responses was the frontal lobe for the control group, and temporal lobe for the VS and MCS groups. CONCLUSIONS: The sudden increase in MMN amplitude and latency shortening may indicate an improvement in the state of consciousness. Neurophysiological evaluations suggest that patients with vegetative state (VS) and minimally conscious state (MCS) may preserve patterns of higher-order cerebral processing similar to those observed in conscious patients.