Unresponsive patients may still be conscious enough to “perform cognitive tests,” a major international study suggests.
Researchers in the United States, Britain and Europe performed MRIs and other brain scans on more than 200 people with severe brain injuries that left them in a coma or vegetative state.
The team asked them to imagine various scenarios such as “opening and closing their hand” to measure brain activity and responses.
They found that one in four participants was likely to repeatedly follow this instruction, suggesting that patients who are largely unaware of what is going on around them may actually be able to understand language, pay attention and perform simple tasks.
The researchers said the findings raise ethical concerns about taking patients off life support or removing their organs too early.
Researchers in four countries found that one in four patients deemed “unresponsive” were able to follow basic instructions, based on brain scans.
The researchers said the findings could prevent patients from being taken off life support too early when they still have signs of consciousness.
Dr Yelena Bodien, lead author of the study and a researcher at Massachusetts General Hospital, said: ‘Some patients with severe brain injuries don’t seem to be processing their external world.
‘However, when assessed with advanced techniques such as task-based fMRI and EEG, we can detect brain activity that suggests otherwise.
‘These results raise crucial ethical, clinical and scientific questions: How can we harness this invisible cognitive ability to establish a communication system and promote greater recovery?’
The study, published Wednesday in the journal New England Journal of Medicineincluded 241 participants from six different sites in the US, UK, Belgium and France.
All of these patients were adults who had suffered some type of brain injury, resulting in a coma, a vegetative state, or a minimally conscious state (in which a person typically exhibits limited signs of consciousness and responses to stimulation).
Most suffered undefined “brain trauma” (traumatic brain injuries, for example), followed by cardiac arrest and stroke.
Patients were on average 38 years old when they were injured and 64 percent were men.
All participants underwent electroencephalograms (EEGs) and MRIs to measure electrical activity and overall brain function. Data was collected over a period of 17 years.
Based on these scans, the team found that 25 percent of participants were able to respond to instructions such as “imagine opening and closing your hand,” followed by “stop imagining opening and closing your hand.”
This is up to 10 percent more than previous estimates, suggesting that more patients may have residual consciousness than previously thought.
The phenomenon is called cognitive motor dissociation (CMD), which occurs when patients appear unresponsive but still have brain activity, such as remembering.
Actress Mamie Laverock was on a ventilator for several weeks after surviving a fall from a five-story building. Despite the improbable odds, she survived and took her first steps (right) after being taken off the ventilator.
Four-year-old Maisie was taken off life support in March, just two days after being admitted to hospital with flu-like symptoms. It is unclear whether she was aware of this or whether keeping her on life support for longer might have improved her chances of survival.
Experts said the findings could help redefine consciousness and prevent patients from being taken off life support or having their organs removed when they have a chance to get better.
Several patients have benefited from being supported for longer periods. For example, Hallmark actress Mamie Laverock was put on a ventilator in May after falling from a fifth-floor balcony.
He remained on life support for several weeks and finally woke up. Three months after the injury, he took his first steps.
Other patients were quickly taken off treatment, so it is difficult to know whether continued support would have allowed them to eventually recover. One shocking case was that of Maisie, a four-year-old girl from Ohio who began to show flu-like symptoms in March.
The preschooler suffered a stroke and severe brain swelling, forcing her to be taken off life support just two days after arriving at the hospital.
“Failure to detect cognitive motor dissociation can have serious consequences, including premature withdrawal of life support, lack of signs of consciousness and lack of access to intensive rehabilitation,” said Dr. Bodien.
Additionally, the findings could encourage doctors to pay more attention to subtle signs of consciousness in their patients or provide them with enrichment, such as playing music or talking to them, that could speed their recovery.
Dr Nicholas Schiff, senior author of the study and a neuroscientist at Weill Cornell Medicine in New York City, said: ‘We found that this type of acute dissociation of retained cognitive abilities and lack of behavioral evidence for them is not uncommon.
“I think we now have an ethical obligation to engage with these patients and try to help them connect to the world.”
However, the study had several limitations, the main one being that each institution followed different procedures to evaluate patients, which could have biased the data.
The study also used a small sample size.
The team plans to conduct additional research to fully explore how conscious patients may be in these states.
“We know that cognitive motor dissociation is not uncommon, but resources and infrastructure are required to optimize detection of this condition and provide appropriate support to patients and their families,” said Dr. Bodien.
