A cheap, portable device may be able to pick up signs of consciousness in patients who have been diagnosed to be in an unresponsive, vegetative state.
Researchers from the University of Western Ontario in Canada measured meaningful brain activity, suggesting full awareness, in three patients who had been previously diagnosed as vegetative and not conscious. The study, which included a total of 16 patients in a persistent vegetative state and 12 healthy controls, used an electroencephalogram (EEG) to measure brain activity in response to verbal commands.
Participants were asked to imagine, at the sound of a tone, making a fist with their right hand. They were also asked to imagine wiggling their toes. In response to each command, the healthy controls showed distinct patterns of activity in the premotor cortex, the part of the brain involved with planning movement. The researchers found that three of the “vegetative” patients showed the same responses.
These patients ranged in age from 20 to 45 years and had different types of injuries. “One of the patients had been in a vegetative state for almost two years and yet he was able to understand what we were trying to do and show he was aware,” study co-author Adrian Owen said in a news briefing.
If the finding holds up in future studies, it could potentially change the standards for diagnosing and treating vegetative patients. It could also open a vital channel for two-way communication between patients and caregivers. Reported New Scientist:
Using EEG to ask questions of these patients is the next step. By assigning thought processes to simple answers — for example, imagining clenching a fist means “yes” and wiggling toes means “no” — the team hopes their work can result in better clinical treatment. “There are some interesting questions that one should get on to right away,” Owen says. “One is, ‘Are you in pain?’”
This isn’t the first time Owen’s team has detected awareness in patients who were thought to have none. Previously, they used functional MRI to show consciousness in such patients, but given the high cost and relative inaccessibility of fMRI scanners, the researchers sought a cheaper way to make diagnoses at the bedside. EEG uses electrodes attached to the head to pick up electrical activity in the brain.
Further study is needed before researchers can be sure that the brain activity seen in these studies was made consciously. Notably, three of the healthy controls failed to register the proper brain activity in response to the verbal commands, even though they were fully aware, which suggests that EEG can’t reliably identify the absence of consciousness.
However, the authors said, it could help identify awareness in patients who would otherwise be missed by standard physical tests, which gauge consciousness by asking people to track moving objects with their eyes or to respond to verbal commands by blinking or twitching a finger. Such tests may lead to misdiagnoses of zero consciousness in people, especially those who have periods of awareness.
“Alongside behavioral assessment and other functional neuroimaging approaches, many testing sessions for several days with this EEG technique will provide each patient with an increased opportunity to show their covert awareness, if it exists,” the researchers wrote.
The study was published online by The Lancet.