Acute brain injury can result in significant damage and loss of consciousness, and it may warrant life support and admission to an intensive care unit. It is when a complex journey towards recovery begins, sometimes it involves daily life and death battles. Once the condition of the patient stabilizes, the question is will they ever wake up?
A recent study provides new insight into the wide spectrum of states between consciousness and unconsciousness, and it opens intriguing possibilities for further research and predicting outcomes. Consciousness is the ability to maintain alertness and to be aware and interact with the surroundings. Physicians prompt patients to follow instructions to assess their level of awareness and delineate signs of consciousness.
It may be simple commands, but it requires a complex array of brain functions in order to be carried out correctly. The hearing needs to be intact and the nerves should be able to tell the respective muscles to function. A tool that can help is an electroencephalogram or EEG, which tests the brain waves. Functional brain imaging such as MRI, is another tool that is used to gain more insight into what is going on inside a brain by monitoring the change in activity of certain areas.
However, none of these means so far has offered an insight into what exactly is going on in the patient's head after suffering an acute brain injury. In the recent study published in the New England Journal of Medicine, neurointensive care physicians and researchers took brain wave analysis to the next level. They connected unresponsive patients with acute brain injury to continuous EEG, and asked them to perform simple commands while their brain waves were being recorded.
The EEG data then were fed into a machine-learning algorithm derived from healthy volunteers, which compared the change in brain activity from the state while at rest to the activity recorded following the commands. Of 104 patients that they studied, 15% of them showed activation of brain activity corresponding to the command, even though bedside examiners did not see any visible response, and it is a phenomenon termed cognitive-motor dissociation.
The researchers also found that patients who showed brain activation were more than three times as likely to make strides in recovery and gain at least partial independence over the year following the brain injury, compared to those who showed no brain activation. They were also nearly twice as likely to be able to demonstrate visible response and follow commands by the end of their stay at the hospital.
This finding is important because, for the first time, scientists could see such a pattern of hidden brain activity in unresponsive patients early after severe brain injury and connect these findings to long-term outcomes, suggesting that such activity might be an early sign for recovery.
It may not have answered the questions about consciousness, but it gave us an idea that cognitive-motor dissociation was not a static phenomenon in patients, but rather inconsistent. Even healthy brains go through phases such as deep sleep where one would likely not activate their brain when asked to do something. There are still a lot of loopholes that needs to be filled, and the findings of this study still need to be replicated in different patients and places.
