EMERGENCE FROM MINIMALLY CONSCIOUS STATE: INSIGHTS FROM EVALUATION OF POSTTRAUMATIC CONFUSION

EMERGENCE FROM MINIMALLY CONSCIOUS STATE: INSIGHTS FROM EVALUATION OF POSTTRAUMATIC CONFUSION To the Editor: We read the article by NakaseRichardson et al.1 with interest. The diagnosis of persistent vegetative state (PVS) has been made more difficult by the recognition of minimally conscious state (MCS) as the transition to partial recovery. Another step is to determine diagnostic criteria to predict emergence from MCS to functional recovery.2,3 Nakase-Richardson et al. investigated the utility of the operational threshold for emergence from posttraumatic MCS by assessing yes/no accuracy to questions of varied difficulty. They concluded that confused patients had difficulty giving accurate answers to simple questions, suggesting that the operational threshold for response accuracy should be revisited as a criterion for emergence from MCS. In addition, questions requiring judgment, even based on old knowledge, were difficult for confused patients. The authors attributed this to inconsistent attention, executive dysfunction, and/or language processing deficits.1 Patients were studied during inpatient rehabilitation. We assessed mother’s voice recognition by PVS and MCS cases using quantitative electric tomography inside hospital settings. Because we found nonreliable responses, we moved our neurophysiologic laboratory setting to patient homes. In a patient with PVS, we recorded a broad activation of the EEG power spectrum when his mother talked to him. No significant differences were found when unknown women spoke to him.4 We suggest that patients should be studied in their home environment using ambulatory neurophysiologic systems. Moreover, the questionnaire proposed by Nakase-Richardson et al.1 could be used for setting paradigms to record event-related potentials,5 and/or activation of the EEG power spectrum,2,4 which might support results from questionnaire screenings for assessing emergence from PVS and MCS.