EEG shows awareness in some vegetative patients
Study using EEG opens new opportunities for communicating, researchers say
Researchers have discovered they can detect conscious awareness in some patients thought to be in a permanent vegetative state using an inexpensive EEG device that measures electrical activity in the brain.
The use of an electroencephalography, or EEG, machine, which can easily be transported to a patient's bedside, follows an earlier breakthrough employing a functional MRI scanner to determine whether some people in a vegetative state were in fact consciously aware but unable to physically respond to stimuli.
"The vegetative state is often referred to as a condition of wakefulness without awareness, and that's because these patients open their eyes, they often appear to look fleetingly around the room, but certainly there's never any signs they're actually aware," said principal researcher Dr. Adrian Owen of the Centre for Brain and Mind at the University of Western Ontario.
"They don't actually respond to anything in the outside world, so you can't attract their attention, you can't make them look in one direction or another," Owen said Wednesday during a webcast to describe the research.
Owen and a team of scientists at the London, Ont., centre, Cambridge University in the U.K., and the University of Liege in Belgium collaborated on this latest research, published online by The Lancet.
Using EEG machines, researchers tested 16 patients who had been diagnosed as being in a vegetative state following brain injury. The patients ranged in age from 29 to 45 and had various types of brain injuries. One man had been unresponsive for almost two years.
After having electrodes attached to their scalp, each patient was first asked to imagine making their right hand into a fist, then to move the toes of both feet. The EEG would record any electrical signals in the brain following each command. Identical EEG testing was performed on 12 healthy volunteers.
Three of the patients repeatedly generated electrical brain activity that matched responses seen in healthy volunteers: the same areas of the pre-frontal cortex, located at or near the top of brain, lit up on a monitor after they were given the two distinct commands.
Adrian Owen talks to Quirks & Quarks, Nov. 12 at noon on CBC Radio One.
"We were able to find that in three of these patients, so nearly 20 percent of the group of patients that we assessed, it was possible to detect that these patients were actually aware," co-author Dr. Damian Cruse of the Brain and Mind Centre explained. "They were able to follow the commands that we were giving them despite the fact that to all external appearances, they appeared to not be aware at all.
"In fact, all the standard clinical assessment of these patients had diagnosed them as being entirely unconscious."
No one has any idea how many people in Canada, or indeed worldwide, are languishing in a vegetative state — or how many of them might be consciously aware but trapped inside their bodies.
But finding out using functional MRI scanners would be economically and logistically impossible, since vegetative patients would have to be transported to the relatively few hospitals that own the highly sophisticated machines, said Owen.
"The move from fMRI to EEG is extremely important for us because it will allow us to get out into the community and answer a simple question like 'How many patients are there?"' he said. "This is something we really don't know. Patients are in care homes, they're in residential homes, they're in hospitals. They're in those situations sometimes for many, many years.
Many families anxious
"Until now, it's not been possible to get out and offer this to patients who are unable to get to a high-field MRI scanner. So for us, this is an exciting possibility to get out there and provide the opportunity to as many of these patients as we can to express themselves if they're conscious."
Since 2006, when their first MRI paper was published, the researchers have been approached by many families anxious to find out if their loved ones in a vegetative state are cognitively aware and somehow capable of communicating.
The team is working on the means for having patients referred for bedside EEG testing, but Owen said there are technical and ethical details to work out first.
Technically, the equipment needs to be improved so electrical brain activity can be analyzed in "real time," instead of taking several hours.
"That's the challenge for the immediate future, to work out how we can speed this up," he said. "And actually only then will somebody really be able to have a conversation in real time with one of these patients."
A number of ethical considerations also need to be explored, including what kind of yes-no questions should be put to patients who turn out to have awareness.
"It opens up a whole world of new opportunities for communicating with these patients and finding out what their inner world is like," Owen said. "And I think it would be a mistake to jump in with both feet and say, 'Right, well, let's start asking them whether they want to live or die, or what they would like to happen to them.'
Ask if they're in pain
"Just because somebody can answer a yes or no question doesn't mean that [we know] everything about their inner mental world — we don't know whether they're depressed, unhappy or happy, or whether they want to live or die."
However, the EEG technique could be used to ask patients if they are in pain, he said. "It's been enormously difficult until now to find out that information. If a patient can't tell you anything, if they can't respond to you, how could you possibly know if they are in any pain?"
Owen said another goal is to see whether brain-computer interface technology being developed may one day be used to unlock the world even more for patients who are cognitively aware but unable to let anybody know.
"Can we get a patient in this situation to communicate with the outside world, to actually spill out words perhaps or to communicate thoughts or desires or wants or needs without us having to decode them in this rather indirect manner of using EEG imagery tasks of hands and toe squeezing?"