Potential Redefinition of “Unresponsive” for People in Hospital With Brain Injuries

The inability to follow a simple command, such as “move your hand” has been termed unresponsive and thought to prognosticate poor neurologic outcomes for those with brain injury. It has not been possible to elucidate whether this status arises from sensory, motor, or cognitive deficits, or a combination of those. Recently there has been evidence that the inability to follow simple commands is because of cognitive-motor dissociation in which functional MRI (fMRI) or electroencephalography (EEG) shows cerebral activation during motor imagery tasks in people who had no motor responses to commands. Another study in 16 individuals with acute traumatic brain injury (TBI) showed both cognitive-motor dissociation and activation of language and higher association areas in response to speech and music. No correlation with clinical functional outcome, however, was seen.

A new study in the New England Journal of Medicine reports that in 104 people with acute brain injury in the intensive care unit, 15% had cognitive-motor dissociation as measured by EEG with a machine-learning algorithm, and that this correlated with improved functional outcomes compared with those who did not have EEG-determined cognitive-motor dissociation. In those with brain injury who had signs EEG signs of motor activation in response to simple commands, there was greater likelihood of reaching at the ability to be left alone for up to 8 hours during the day without assistance 12 months after injury.

Signatures of the ability to follow a simple command were measured in 10 healthy volunteers and those with brain injury. Many of the individuals with brain injury were receiving sedative drugs, and multiple assessments showed detection of these EEG signatures was inconsistent. 

Although validation of the methodology and replication of results is needed to generalize these findings, this initial study suggests that EEG signatures could be used prognosticate outcomes more accurately for the benefit of patients and their families.