Emergence from minimally conscious state: insights from evaluation of posttraumatic confusion.

BACKGROUND: Guidelines for defining the minimally conscious state (MCS) specify behaviors that characterize emergence, including "reliable and consistent" functional communication (accurate yes/no responding). Guidelines were developed by consensus because of lack of empirical data.
OBJECTIVE: To evaluate the utility of the operational threshold for emergence from posttraumatic MCS, by determining yes/no accuracy to questions of varied difficulty, including simple orientation questions, using all items from the Yes/No Subscale of the Mississippi Aphasia Screening Test.
METHOD: Prospective observational study of a cohort of responsive patients recovering from traumatic brain injury in an acute inpatient brain injury rehabilitation program.
RESULTS: Of the 629 observations from 144 participants, name recognition was the easiest yes/no question, with nonconfused individuals responding with 100% accuracy, whereas only 75% to 78% of confused participants on initial evaluation answered this question correctly. Generalized Estimating Equations analysis revealed that confused participants were more likely to respond inaccurately to all yes/no questions. Nonconfused participants had a reduction in odds of inaccuracy ranging from 45.6% to 99.7% (p = 0.001 to 0.02) depending on the type of yes/no question.
CONCLUSIONS: Accuracy for simple orientation yes/no questions remains challenging for responsive patients in early recovery from traumatic brain injury. Although name recognition questions are relatively easier than other types of yes/no questions, including situational orientation questions, confused patients still may answer these incorrectly. Results suggest the operational threshold for yes/no response accuracy as a diagnostic criterion for emergence from the minimally conscious state should be revisited, with particular consideration of the type of yes/no questions and the requisite accuracy threshold for responses.