A simple measurement using a device available in every
hospital could distinguish brain damaged patients who are likely to “wake up”
from those who are not, scientists reported on Thursday.
Predicting which unconscious patients will remain that way
forever and who is likely to recover is so difficult that even expert
physicians get it wrong in about 40 percent of cases, said Dr. Nicholas Schiff
of Weill Cornell Medical Center in New York City, who was not involved in the
new study.
As a result, tens of thousands of patients are discharged
from hospitals and “shunted off to nursing homes and other institutions” where
they are treated as living corpses, kept alive but given no therapy that might
bring them back to conscious life, Schiff said.
The new study, which he called “rigorous and extremely well
done,” offers a “direct, simple approach that could be adopted tomorrow.”
An estimated 200,000 to 300,000 people in the United States
are living in that gray area between life and death — either in an unresponsive
wakefulness state (previously called a vegetative state) or a minimally
conscious state. In the former, people look awake but are wholly unaware of
their surroundings and do not consciously respond to sights, sounds, or touch.
Those in a minimally conscious state sometimes respond to a command or other
stimulus, but often do not — hence the difficulty in distinguishing the two.
But the latter are much more likely to regain consciousness.
Diagnosing via behavioral measures is “susceptible to
interpretational bias,” said Ron Kupers. So he along with colleagues at the
University of Copenhagen set out to “find more objective measures” to
distinguish these two states. They used positon emission tomography, or PET,
imaging, which measures brain metabolism, to try to distinguish brains that
appeared equally unconscious but that might have different capacities for
recovery.
The scientists tested the technique on 131 brain-injured
patients: 49 in a vegetative state, 65 who were minimally conscious, and 17 who
were emerging from a minimally conscious state. No single region was associated
with likelihood of regaining consciousness — that is, the brain does not have a
“consciousness center.”
But overall metabolism did show a difference. Vegetative
patients had, on average, 38 percent of the brain activity that healthy people
did. Minimally conscious patients had 56 percent, the researchers report in the
journal Current Biology.
Arguably even more important, PET predicted whether a
patient would recover awareness within a year. The cutoff: Brain activity at
least 41 percent of that in healthy people. Using that rule of thumb
researchers correctly identified 94 percent of the patients who would recover
within 12 months.
That suggests that at a high enough metabolism, the brain
flips from one fundamental state (unconsciousness) to another (consciousness)
rather than changing gradually.
A previous study by some of the same researchers had found
that PET scans could correctly predict regained consciousness 74 percent of the
time. This study improved upon that rate.
https://www.statnews.com/2016/05/26/brain-scans-consciousness-vegetative/
Courtesy of Doximity
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