NEJM: Functional MRI + mental tasks may indicate awareness for vegetative patients
A combined technique utilizing functional MRI and mental-imagery tasks have proven that a small proportion of patients diagnosed as being in a vegetative or minimally conscious state may have brain activity reflecting some awareness and cognition, according to the results of a study published online Feb. 3 in the New England Journal of Medicine.
The study's lead author Martin Monti, PhD, a neuroscientist at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, England, and colleagues enrolled 54 patients for their study that were previously diagnosed with disorders of consciousness.
At two major referral centers in Cambridge, England and Liege, Belgium, the researchers administered mental-imagery tasks, which included asking the patients to think about hitting a tennis ball or walking around their home or neighborhood, while undergoing functional MRI to assess each patient’s ability to generate willful, neuroanatomically specific, blood-oxygenation-level–dependent responses. The authors then developed a technique to determine whether such tasks could be used to communicate “yes” or “no” answers to simple questions.
Of the 54 patients, five were found to have the ability to “willfully modulate their brain activity, or show evidence of conscious thought,” said the authors, who reached this conclusion after comparing the patients' brain activity to that of healthy controls performing the same mental tasks.
Of these five patients, three patients--two of whom had been considered vegetative and one minimally conscious--were noted as revealing signs of awareness, such as following commands or making small movements during bedside clinical testing in addition to the MRI testing, but the remaining two patients displayed no further signs of awareness during bedside clinical assessment.
Moreover, the authors wrote that one patient, a man in his twenties who had suffered traumatic brain injury as a result of a car accident at least five years earlier, was able to use the established technique to answer “yes” or “no” to questions during functional MRI, but noted that they did not establish any form of communication at the bedside.
Four patients who were originally diagnosed as being in a vegetative state were reclassified as being minimally conscious as a result of the study, noted Monti and colleagues.
“The rate of misdiagnosis is approximately 40 percent, and new methods are required to complement bedside testing, particularly if the patient’s capacity to show behavioral signs of awareness is diminished,” wrote the authors.
“This technique may be useful in establishing basic communication with patients who appear to be unresponsive,” said Monti and colleagues, who also warned that the research may raise more questions than answers. “The human brain, even though we are learning more and more about it, is extremely mysterious to us in many ways," they concluded. "We are still struggling to understand the meaning of what it means to be conscious or to have streams of thought or self- awareness."
The study's lead author Martin Monti, PhD, a neuroscientist at the Medical Research Council Cognition and Brain Sciences Unit in Cambridge, England, and colleagues enrolled 54 patients for their study that were previously diagnosed with disorders of consciousness.
At two major referral centers in Cambridge, England and Liege, Belgium, the researchers administered mental-imagery tasks, which included asking the patients to think about hitting a tennis ball or walking around their home or neighborhood, while undergoing functional MRI to assess each patient’s ability to generate willful, neuroanatomically specific, blood-oxygenation-level–dependent responses. The authors then developed a technique to determine whether such tasks could be used to communicate “yes” or “no” answers to simple questions.
Of the 54 patients, five were found to have the ability to “willfully modulate their brain activity, or show evidence of conscious thought,” said the authors, who reached this conclusion after comparing the patients' brain activity to that of healthy controls performing the same mental tasks.
Of these five patients, three patients--two of whom had been considered vegetative and one minimally conscious--were noted as revealing signs of awareness, such as following commands or making small movements during bedside clinical testing in addition to the MRI testing, but the remaining two patients displayed no further signs of awareness during bedside clinical assessment.
Moreover, the authors wrote that one patient, a man in his twenties who had suffered traumatic brain injury as a result of a car accident at least five years earlier, was able to use the established technique to answer “yes” or “no” to questions during functional MRI, but noted that they did not establish any form of communication at the bedside.
Four patients who were originally diagnosed as being in a vegetative state were reclassified as being minimally conscious as a result of the study, noted Monti and colleagues.
“The rate of misdiagnosis is approximately 40 percent, and new methods are required to complement bedside testing, particularly if the patient’s capacity to show behavioral signs of awareness is diminished,” wrote the authors.
“This technique may be useful in establishing basic communication with patients who appear to be unresponsive,” said Monti and colleagues, who also warned that the research may raise more questions than answers. “The human brain, even though we are learning more and more about it, is extremely mysterious to us in many ways," they concluded. "We are still struggling to understand the meaning of what it means to be conscious or to have streams of thought or self- awareness."