Emerging from a coma: Response to language can help assess states of consciousness
A man—for the sake of this exercise, let's call him "Paul"—has a heart attack and his brain is starved of oxygen. After several resuscitations and a week in a coma, he finally opens his eyes. However, he doesn't always ...
Recent advances in intensive-care medicine have allowed many people with severe brain injuries to "come back to life." However, from a seemingly inert state to full wakefulness, there is a wide range of different states of consciousness that neuroscientists are working to better define.
After a coma episode (where the eyes remain closed) lasting between one hour and four weeks, there are normally several states of recovery until "emergence," but some intermediate states of consciousness may persist and even become chronic:
Unresponsive wakefulness syndrome: the patients open their eyes but show no signs of consciousness. (This was previously called a "vegetative state," but was renamed in 2010 to better describe the symptoms.)
Minimally conscious state "minus": recovery of some signs of consciousness such as visual pursuit/fixation, or localization of painful stimulation.
Minimally conscious state "plus": reappearance of signs of language awareness—response to verbal commands, production of words, attempts to communicate.
Emergence from the minimally conscious state: as soon as the patient is able to communicate using a yes/no code or to use everyday objects.
It is crucial to be able to distinguish these disorders of consciousness from a locked-in syndrome, also the result of a severe brain injury, but located in the brain stem. The result is paralysis of the body, head and face, although consciousness and cognition may be preserved. Communication is most often achieved through eye movements.
An EEG and MRI allow physicians to follow the activity of the cerebral regions linked to language. This enables them to measure the reactions of a patient in a state of minimal consciousness to various commands. Credit: Gorodenkoff/Shutterstock
Diagnosis of the state of consciousness following brain damage: coma, unresponsive wakefulness syndrome (vegetative state), minimally conscious state minus, minimally conscious state plus and emergence. Credit: Wislowska et al. (2017). Night and day variations of sleep in patients with disorders of consciousness
Passive vs. active tasks to identify language comprehension in awake coma patients. The former are based on EEG and MRI and assess brain activity in response to different language stimuli; the latter measure the ability to respond to verbal commands, either behaviourally or via EEG and MRI. Credit: Charlène Aubinet
One-third and one-fifth of patients with an unresponsive wakefulness syndrome (UWS) respond to passive and active tasks, respectively. As their level of consciousness increases, through the minimally conscious state (MCS) and up to the emergence from the minimally conscious state (EMCS), more residual language abilities are observed in patients. Credit: Charlène Aubinet