Mirroring of a simple motor behavior in disorders of consciousness.

Objective: In patients suffering from Disorders of Consciousness (DOC) electrophysiological recordings at bedside could serve as a complimentary and economical tool to improve diagnosis. We utilized a motor observation and imagination paradigm to gain new insights on preserved cognitive processing in DOC.

Methods: EEG brain oscillations were analyzed in 10 VS/UWS (Vegetative State/Unresponsive Wakefulness Syndrome) patients and 7 MCS (Minimally Conscious State) patients and 21 controls during observation and imagination of a grasping movement and group statistics were conducted.

Results: While control subjects showed a typical desynchronization at 8-15Hz during observation of a movement, MCS patients presented an analogue response at 8-10Hz, but exhibited a synchronization at 12-15Hz. The VS group did not show a systematic response. Imagery-related activation was only sustained for 1500ms even in control subjects, therefore, limiting conclusions regarding the ability to follow an instruction. Furthermore, a clinically diagnosed VS patient exhibited EEG responses indicative for MCS.

Conclusion: Results indicate that MCS patients are still able to process an observed motor behavior on a basic sensory and perhaps even pre-motoric level, but seem not to be capable of "mirroring" the movement like healthy participants.

Significance: "Real-world" tasks as presented here carry the potential to identify residual cognitive functioning in DOC patients and may ultimately help to lower misdiagnosis rates.