Doctors may be able to tell whether a patient is in a vegetative or minimally conscious state by tracking signals on a path through the brain, a study said.
The findings could lead to a new diagnostic tool to help doctors with life-support decisions in cases such as that of Terri Schiavo, the Florida woman who was in a vegetative state for 15 years before a court ordered her feeding tube removed. The study, by researchers from the University of Liege in Belgium, is published in the journal Science.
It can be difficult to differentiate between people in a vegetative state, in which patients lack cognitive function though display forms of wakefulness, and a less serious impairment that leaves patients minimally conscious yet often able to communicate in some form. This medical dilemma led to a legal battle in the case of Schiavo, who fell into a coma in 1990 and died in 2005.
“This is one step further in understanding the brain function in these patients, and it gets closer to a diagnostic tool,” said Melanie Boly, the study’s first author and a post- doctoral researcher at the Coma Science Group at the University of Liege in Belgium, in a telephone interview. “This may be convenient to use clinically because you can bring the technique to the patient’s bedside.”
More study with more patients will be required to determine whether the method can be used as a diagnostic measure, said Nicholas Schiff, a professor of neurology and neuroscience at Weill Cornell Medical College in New York. Diagnostic measures have a higher standard of proof than this study demonstrates, he said.
Insight Not Diagnostic
“It’s really a kind of an insight,” said Schiff in a telephone interview. “In patients who are clearly vegetative or clearly minimally conscious, do you see a biological distinction?”
The researchers used electroencephalogram recordings of brain activity from 22 healthy volunteers, 8 patients in vegetative states and 13 in minimally conscious states to model brain activity. The EEG recordings were taken while subjects listened to tones. They were then placed in a mathematical model to determine what the recordings meant.
Most people’s brains process sounds by sending signals “up” to the front of the brain, in the parietal and frontal cortex, to locate the type of sound, identify it, and make decisions. The signal is then sent down to the temporal cortex, in a feedback loop. The model showed vegetative state patients didn’t complete the loop. The healthy subjects and minimally conscious patients did.
“What it’s saying, in simpler terms, is that these patients had a more profoundly impaired frontal part of their brain,” Schiff said. “It’s an elegant, nice study, and it does comport nicely with a lot of other work.”
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