CAMBRIDGE, England -- A woman thought to be in a persistent vegetative state showed evidence of awareness of herself and her environment in response to verbal commands, said researchers here.
CAMBRIDGE, England, Sept. 8 -- A woman thought to be in a persistent vegetative state showed evidence of awareness of herself and her environment in response to verbal commands, said researchers here.
The report stirred memories of the infamous Terri Schiavo case. Schiavo was the woman in a persistent vegetative state who was the focus of a medical and political storm last year, pitting her husband and so-called death-with-dignity proponents against her parents and so-called right-to-life advocates.
The investigators here used functional MRI to evaluate a 23-year-old woman's brain activity, if any, during the presentation of simple spoken sentences. The scans were compared with others taken when the patient was presented with acoustically-matched noise sequences.
The woman had been unresponsive since emerging from a coma after a traffic accident and met all the criteria for a persistent vegetative state. When she was presented with spoken sentences she had increased activity in speech comprehension centers in the brain, as seen on functional MRI.
And when she was asked to imagine herself playing tennis and walking through the rooms of her house, brain areas governing visuospatial and motor function lit up on the imaging screen, in patterns similar to those seen in normal volunteers, reported Adrian M. Owen, Ph.D., and colleagues of Cambridge University and the University of Liege, Belgium, in the Sept. 8 issue of Science.
"Despite fulfilling the clinical criteria for a diagnosis of vegetative state," the authors wrote, "this patient retained the ability to understand spoken commands and to respond to them through her brain activity, rather than through speech or movement. Moreover, her decision to cooperate with the authors by imagining particular tasks when asked to do so represents a clear act of intention, which confirmed beyond any doubt that she was consciously aware of herself and her surroundings."
"It's a spectacular result," said Nicholas D. Schiff, M.D., assistant professor of neurology and neuroscience at the Weill Cornell Medical College in New York, in a news article in the same issue of Science.
It's not clear, however, whether the results could be reproduced in other patients diagnosed as being in persistent vegetative states, Dr. Schiff said.
The Schiavo case ended with the courts granting her husband, Michael Schiavo, the right to withhold life-sustaining treatment, but not before Senate Majority Leader Bill Frist, M.D., in a memorable moment in political theatre, declared on the Senate floor "that is not somebody in persistent vegetative state. . . . There just seems to be insufficient information to conclude that Terri Schiavo is [in a] persistent vegetative state."
Dr. Frist later acknowledged to reporters that Schiavo had suffered from severe brain injury and atrophy, and defended his actions by saying that "I never, never, on the floor of the Senate, made a diagnosis, nor would I ever do that."
The case here was reported in a one-page article. Hoping to avoid a flare-up of the Schiavo imbroglio, the editors of Science, in a statement issued to the media, noted that the paper is a single case report, "and therefore should not be used to generalize about all other patients in a vegetative state, particularly since each case may involve a different type of injury."
According to the National Institute for Neurological Disorders and Stroke (NINDS) people who are in a persistent vegetative state have lost their cognitive abilities and awareness of their surroundings, but retain non-cognitive function and normal sleep patterns. Although patients in a persistent vegetative state may move, grunt, cry, or laugh, the diagnosis hinges on an absence of reproducible evidence that such movements or behaviors are purposeful responses to external stimuli.
"Recent functional neuroimaging studies have suggested that 'islands' of preserved brain function may exist in a small percentage of patients who have been diagnosed as vegetative," Dr. Owen and colleagues wrote. "On this basis, we hypothesized that this technique also may provide a means for detecting conscious awareness in patients who are assumed to be vegetative yet retain cognitive abilities that have evaded detection using standard clinical methods."
The functional MRI scans showed activation bilaterally in the middle temporal gyrus and superior temporal gyrus in apparent response to intelligible speech. The activity was similar to that seen in scans of healthy volunteers, the authors noted.
When the patient was presented with sentences containing ambiguous words (such as homophones that could be mistaken for other words when taken out of context), the scan showed activity in the left inferior frontal region, reflecting, the authors contended, semantic process important for speech comprehension.
"An appropriate neural response to the meaning of spoken sentences, although suggestive, is not unequivocal evidence that a person is consciously aware," they acknowledged. "For example, many studies of implicit learning and priming, as well as studies of learning during anesthesia and sleep, have demonstrated that aspects of human cognition, including speech perception and semantic processing, can go on in the absence of conscious awareness."
To determine whether the patient might exhibit evidence of conscious awareness, they presented her with spoken instructions to imagine herself playing a game of tennis, and to think of herself visiting all the rooms of her house, starting from the front door.
Scans taken when she was asked to play an imaginary game of tennis revealed significant activity in the supplementary motor area, whereas imaging performed during the imaginary house tour lit up sections of the parahippocampal gyrus, the posterior parietal cortex, and the lateral premotor cortex, regions mapped to visuospatial tasks. Again, the responses were similar to those seem with healthy volunteers asked to perform the same tasks.
The investigators asserted that "her decision to cooperate with the authors by imagining particular tasks when asked to do so represents a clear act of intention, which confirmed beyond any doubt that she was consciously aware of herself and her surroundings."
They argued that because false negative findings are common in functional neuroimaging studies, the absence of similar findings cannot be construed to indicate a lack of awareness in similar patients.
The findings suggest that it might be possible for patients who have been diagnosed as being in minimally conscious states or locked in due to degenerative neuromuscular disorders to "use their residual cognitive capabilities to communicate their thoughts to those around them by modulating their own neural activity," Dr. Owen and colleagues postulated.
Related Content:Sleep Disorders