In treating severely brain-damaged patients, doctors often face the difficult task of determining whether those who appear to be in a vegetative state show, or will ever show, signs of brain activity — a decision previous studies have shown they fail to make correctly 40 percent of the time.
New research, however, shows that a three-dimensional brain imaging technique called positron emission tomography (PET) can lower that rate by more accurately telling whether patients in vegetative states show signs of awareness than traditional methods that rely on testing patients’ responsiveness to aural, visual and other behavioral cues.
“Our findings suggest that PET imaging can reveal cognitive processes that aren’t visible through traditional bedside tests, and could substantially complement standard behavioral assessments to identify unresponsive or ‘vegetative’ patients who have the potential for long-term recovery,” said Dr. Steven Laureys, director of the Coma Science Group at the University of Liège in Belgium and lead author of the study, published in The Lancet on Wednesday.
According to neuroscientists Jamie Sleigh of the University of Auckland and Catherine Warnaby of the University of Oxford, “Prediction of outcome on the basis of standard clinical examination and structural brain imaging is probably little better than flipping a coin” in patients with swelling of the brain, they wrote in an editorial that accompanied the study.
Laureys and his team used PET imaging, which allows scientists to visually track the brain’s metabolizing of glucose, a sign of brain function, to examine 122 patients. Of them, 41 had previously been diagnosed as being in a vegetative state; the other 81 had been diagnosed as being in a “minimally conscious state,” meaning they had fluctuating awareness and might respond to some stimuli. It’s the minimally conscious patients who have the most hope of recovery, the authors said.
Their PET tests revealed that one-third of the patients previously diagnosed by traditional methods as being in a vegetative state actually showed signs of brain activity that implied some level of consciousness existed.
When the team followed up with those patients one year later, nine of them had recovered a “reasonable level of consciousness,” according to the study.
“We confirm that a small but substantial proportion of behaviorally unresponsive patients retain brain activity compatible with awareness,” Laureys said.
The scientists also used MRI technology to monitor brain activity, but this type of imaging wasn’t as accurate as the PET.
The researchers say their findings have strong implications for how doctors may choose to assess brain-damaged patients. However, the authors of the study cautioned that brain-imaging techniques shouldn’t stand alone, but should be combined with behavioral assessments.
Families of seemingly unresponsive patients may also find it less difficult to decide whether to maintain life support services if they’re able to see brain scans that register activity.
For example, the nation was transfixed in 2005 by a legal battle between the husband of Terri Schiavo, a Florida woman whose doctors had diagnosed her as being in a persistent vegetative state, and her family, who did not want her feeding tube removed, insisting that she showed signs of awareness. Doctors eventually removed her from life support.
And in 2013, the family of a brain-dead pregnant woman battled with a Fort Worth, Texas, hospital over whether she should be removed from life support. The hospital complied with her family’s wishes to shut off the system after a court ruled she was legally dead.
“Because these states occupy a border zone between awareness and consciousness, the distinction between them has important ethical and therapeutic implications,” the authors of the study wrote.