Assessing consciousness with auditory event-related potential during coma recovery: a case study.

To observe changes in mismatch negativity (MMN) and P300 in a patient transitioning from a vegetative state (VS) to a minimally conscious state (MCS). One patient with intracerebral hemorrhage and an 8-month disease course was evaluated as being in the VS using the Coma Recovery Scale-Revised. Two weeks after the patient was admitted to the hospital, another evaluation was performed, and the patient was determined to be in an MCS. Using the Oddball paradigm, pure tone and name stimuli were presented to the patient to study event-related potentials (ERPs). A 15-week clinical follow-up was carried out, and four ERP examinations were performed at 2 days and 2, 6, and 15 weeks after admission. One healthy individual was assessed as a control participant. MMN and P300 were elicited in all four ERP examinations. MMN and P300 may occur earlier than believed in patients in persistent VS and MCS; their predictive values for prognosis need to be further confirmed by follow-up studies on a large clinical sample.