Information processing in patients in vegetative and minimally conscious states.

Objective: Evaluation of a short two-tone oddball paradigm to discriminate between the vegetative state (VS) and minimal consciousness state (MCS) in a sample of patients with severe disorders of consciousness (DOC).

Method: EEG was recorded from 45 DOC patients and 14 healthy participants while listening to an auditory oddball paradigm presented in a passive - just listen - and an active - count the odd tones - condition. In patients, the experiment was repeated after a minimum of one week.

Results: Prevalence of the P300 was higher in healthy participants (71%) than in patients, but did not discriminate between VS (T1: ∼10%; T2: ∼11%) and MCS (T1: ∼13%; T2: 25%) patients.

Conclusion: Results cast doubt on whether this simple auditory stimulation paradigm, which requires cognitive action from the listener, is sensitive enough to discriminate between patients with DOC.

Significance: The sensitivity of the P300 ERP obtained in a short two-tone oddball paradigm presented in a passive and an active condition appears to be too low for routine application in a clinical setting aiming at distinguishing between VS and MCS patients.