|
|
How to ‘unlock’ the brains of coma patients
There will be few who didn’t shiver when they heard the story of Rom Houben, a 46-year old Belgian man believed to be in a coma for over 20 years, who it has now emerged was conscious the whole time.
How many other people are out there, imprisoned by their own bodies? How might we discover more of them?
Apart from avoiding a repeat of Houben’s nightmare, being able to detect full, and residual, consciousness in patients who are apparently comatose is important for other reasons.
It can change how someone who is paralysed is treated, whether their relatives continue to try and communicate with them, what medication they are given, and even the biggest decision of all; whether or not to keep them alive.
After a near-fatal car crash in 1983, doctors presumed Houben was in a
vegetative state, in which he could feel or hear nothing.How many other people are out there, imprisoned by their own bodies? How might we discover more of them?
Apart from avoiding a repeat of Houben’s nightmare, being able to detect full, and residual, consciousness in patients who are apparently comatose is important for other reasons.
It can change how someone who is paralysed is treated, whether their relatives continue to try and communicate with them, what medication they are given, and even the biggest decision of all; whether or not to keep them alive.
But recently Steven Laureys, a leading coma researcher at the University of Liège in Belgium, discovered using a brain scan that Houben was completely conscious, just paralysed.
He has since been provided with a special touchscreen, which he uses to communicate using residual movement in a finger.
“Powerlessness. Utter powerlessness. At first I was angry, then I learned to live with it,” Houben tapped out on to the screen during an interview, according to the Associated Press.
Wired is now reporting that “these may not be his words at all” because they are delivered with assistance from an aide who helps guide his finger to the letters on the touchscreen, a technique known as “facilitated communication”.
However, Wired also says that, even though Houben is not actually constructing these sentences, this “does not alter the fact of his misdiagnosis”.
Consciousness, because it is subjective, is extremely difficult to detect.
Earlier this year, Laureys, together with other researchers, made a step towards this goal when he re-diagnosed 44 patients thought to be in a vegetative state and found that 18, or 41 per cent, were in fact “minimally conscious”, a kind of twilight zone between consciousness and unconsciousness, in which pain can be felt and recovery to full consciousness is more likely.
They concluded that many more people currently presumed to be brain-dead, may, like Houben, have residual or even full consciousness.
The tool they used was the Coma Recovery Scale-Revisited (CRSR), a systematic set of behavioural tests and the only tool specifically designed to tell the difference between a vegetative and minimally conscious state.
As well as guarding against missing awareness in someone who pops in and out of consciousness, or mistaking a reflexive response for a response based on consciousness, the CRSR makes use of some new insights, such as using a mirror to see how someone responds to a reflection of themselves.
But in addition to better behavioural tests, another option for avoiding cases like Houben’s is to use a brain scan to find some signature of consciousness. This would work like a “consciousness meter” that doesn’t rely on a doctor’s subjective assessment.
Laureys discovered Houben was conscious when his brain was scanned using functional magnetic resonance (fMRI) imaging, which revealed that it was “functioning almost normally”, according to The Guardian.
Brain scans were also used in another study in 2006, when Laureys, together with Adrian Owen of the University of Cambridge showed that some patients in a vegetative state show certain patterns of brain activity that suggest they can understand speech.
The brain of one patient, thought to be in a vegetative state, responded differently when she was asked to imagine playing or moving around her home, indicating that she could understand the task - and was obeying it.
Laureys is also working on finding a consciousness signature using the default mode network, a network of brain regions that is active when we daydream.
In 2008, he reported that activity in this network varied in proportion to the amount of brain damage. Minimally conscious patients had a 10 per cent reduction compared with healthy individuals, activity was reduced by 35 per cent in coma patients and those in a persistent vegetative state (PVS), and there was no activity at all in the default network of a brain-dead patient.
Patients in the minimally conscious state were also shown recently to be capable of learning, a finding that might also help to distinguish them from patients in a vegetative state, and that might even help them recover.
It’s never going to be easy to detect consciousness - but by raising awareness of the problem, and exploring a variety of consciousness signatures based on behavioural tests and brain scans - hopefully we can start “unlocking” more people like Houben.
