Coma study will not give all answers to relatives
ANALYSIS:People in long-term comas may be able, after all, to communicate. What are the implications? asks MUIRIS HOUSTON
THE PUBLICATION yesterday of a landmark paper on human consciousness by the New England Journal of Medicinehas, not unexpectedly, sparked considerable interest. Persistent vegetative state is an emotive area and this research will lead to some soul searching for families of patients who have been in a coma for a prolonged period.
Doctors from specialist centres at the University of Cambridge and the University of Liège in Belgium carried out additional tests on 54 patients who had been comatose for some time. All had a severe brain injury; for some it was the result of lack of oxygen to the brain, while others had sustained severe trauma to the brain. Improvements in intensive care have led to a significant increase in the number of people surviving severe brain injury.
Researchers carried out functional magnetic resonance imaging (MRI) on the brains of those selected. A specialist form of MRI scan, the test gives “real time” feedback on activity in different parts of the brain. Those tested were asked to perform imagery tasks such as imagining they were on a tennis court and were hitting a tennis ball back and forth. Patients were also asked questions requiring a yes or no response, while the researchers watched for an MRI response in a particular part of the brain.
Some five of the 54 patients were able to wilfully modulate their brain activity. A single patient was able to answer yes or no to questions during functional MRI, something he was unable to do during regular bedside testing without the scan.
Another significant finding was that all five patients who altered their brain activity had suffered traumatic brain injury, while none of those in a coma who were brain injured following oxygen starvation to the brain were able to respond.
What is left of the human being when the brain is badly damaged has largely been a question for philosophers and theologians. But this latest research has unveiled a form of preserved cognition in people who exist in a minimally conscious or vegetative
state. And even though the phenomenon was found in just five of 54 people tested it still occurred often enough that it will now be difficult for doctors to tell families confidently that their unresponsive loved ones are not “in there somewhere”.
A clinical diagnosis of the vegetative state, using bedside testing is inaccurate some 40 per cent of the time. Indeed, in this study a careful re-examination of the five patients with a functional MRI response found that three of them actually had clinical evidence of awareness and cognition.
At the very least the results suggest that functional MRI might supplement clinical examination in the classification and prognosis of patients with coma.
But for loved ones, the new reality may not be as straightforward. Watching a relative or friend in a vegetative or minimally conscious state is distressing. Will these findings help?
An obvious use of mental signalling by means of functional MRI could be to preserve the patient’s autonomy by asking what they would like in terms of continued medical
care. At the other extreme, a lack of response to functional MRI testing may help persuade families who interpret eye movement, yawning and other reflex responses as implying mental functioning, that this is not in fact the case.
However it may be more difficult to prove a lack of cognition than to demonstrate its presence.
It would be easy to over-interpret and sensationalise this ground-breaking research on clinically undetected consciousness.
There are three fundamental findings: firstly brain activation was detected in very few patients; activation was found only in some patients with traumatic brain injury, and not at all in patients suffering brain injury as a result of widespread lack of blood and oxygen supply; and we cannot be sure that cortical activation provides evidence of “stream of thought” memory, self-awareness,and reflection.
In particular, the new technique cannot tell us whether the patient is aware of their predicament. And it would be especially dangerous to use it to judge the quality of any person’s inner life. Inevitably, however, some relatives will interpret the research to justify continued and unqualified life support in unresponsive patients. If this was to happen on a widespread scale, it could lead to unexpected pressure on intensive care beds and facilities.
While a functional imaging system will now have to be developed to classify unresponsive patients, it will still be subject to the same risks of false positive and false negative testing that bedevil all medical testing. And medicine will have to develop a new system of classifying unconsciousness. It may no longer be acceptable to have a continuum from conscious to unconscious as we have at present.
This research brings us closer to defining where brain function ends and mindfulness begins. But, as an editorial accompanying the research suggests we are a long way from being able to state: “I have brain activation, therefore I am.”
Dr Muiris Houston is a columnist with The Irish Times