Scientists may have found a way to detect the inclusions of consciousness in comatose and vegetative patients just days after they experienced brain damage. It seems that the method can help to predict which patients will recover and recover during the months afterwards.
A team of researchers in New York recorded electrical activity in the brains of non-responsive patients, while giving them simple spoken commands, such as "continue to open and close your right hand" or "twist your toes". Of 104 unreacted patients, 16% tested showed some activity. Of the 16 patients, eight of them (50%) continued to be able to follow spoken commands when they left the hospital. One year later, seven of them (44%) could work independently for at least eight hours at a time.
On the other hand, only 14% of those who did not show any electrical activity at an early stage reached this level of recovery after one year. The results were published this week in the New England Journal of Medicine.
The study was small, and the authors warn that the results "require validation in larger multi-center studies that are effective in detecting differences in long-term results". But if the results continue, the study can offer clinicians a way to help assess which patients can come from a coma or vegetative state.
The study is not the first to discover that some different patients exhibit brain activity to spoken commands that do not seem to be translated into behavior, that is, they actually angle the toes for example. Researchers call such a "cognitive-motor dissociation", and a 2016 meta-analysis of dozens of studies has estimated that it occurs in about 14% of chronically unresponsive patients. It is close to the occurrence found by the New York team.
The electrical activity seems to be a response to the spoken commands and perhaps the brain is recognizable and tries to actually execute the orders. But, as the New York researchers note, "whether the detected signal represents recognition or understanding of commands is uncertain." Researchers are also uncertain as to whether the detected activity has any significance for the patients' results.
The new study tries to get this issue by following up the patient over a year. All work was done in a single intensive care unit with patients taken between 2014 and 2017. Oreceptive patients were screened and tested during the first few days at the hospital. Researchers registered patients who were in coma, in a vegetative state or in a "minimally conscious state-minus" condition, where some low behaviors are maintained. These include being able to follow moving objects with their eyes, visually fix and react to pain or discomfort.
The cause of these conditions in the enrolled 104 non-responsive patients varied. Some patients had experienced cardiac arrest, while others had suffered traumatic brain damage or bleeding.
The researchers used a common, relatively easy-to-use test to assess brain activity: an electroencephalogram. Also known as EEG, picks up electrical pulses using electrodes attached to the scalp (in this case, a standard assembly of 21 electrodes is used). EEG is often used to diagnose epilepsy, assess brain activity after stroke or during sleep disturbances.
The researchers conducted the tests in 25-minute spoken command sessions, testing the 104 responding patients together with 10 healthy people as a control group. Of the responding patients, 16 showed electrical activity while 88 did not. In the following year, six died with EEG activity and 50 without it, some because they were away from life support (four and 24 respectively).
But seven of the original 16 with EEG activity rallied and reached a recovery level that was scored as 4 or higher on the Extended Glasgow Outcome Scale. This is a clinical scale that ranks the results of brain damage from 1 (death) to 8 ("upper bra"), which is generally a resumption of normal life. A score of 4 is considered "top serious disability." Patients with this score are dependent on daily support but can be left at home alone for eight or more hours. While 44% (seven patients) with EEG activity after injury made it 4 or higher in one year, only 14% (12 of 88 patients) without EEG had a 4 or higher. The study was not large enough to link such results to any causes of brain damage.
NEJM, 2019. DOI: 10.1056 / NEJMoa1812757 (To DOIs).