Study of vegetative patients is ‘flawed’
Canadian test detecting awareness can lead to false positives, scientists say
A famous Canadian study claiming that a simple bedside test could detect awareness in patients believed locked in a vegetative state was flawed and the findings were most probably the result of chance, says a new analysis of the data.
U.S. researchers, reporting in The Lancet, the same journal that published the original study, say the widely publicized paper by brain scientists at Western University in London, Ont., who used an electroencephalogram (EEG) to detect brain activity in vegetative patients, may have raised false hopes about whether patients thought to be entirely unconscious are, in fact, aware and capable of communicating with the outside world.
Instead, the U.S. team says their second look at the data revealed only random fluctuations in brain activity — not meaningful brain signals.
“We see the urgency and need every single day for tests that can be used to help establish awareness and consciousness in brain-injured patients,” said co-author Dr. Nicholas Schiff, a neurologist at New York–Presbyterian Hospital and Weill Cornell Medical Centre.
“However, we won’t help patients or their families by using a flawed research method and data that cannot accurately provide the information we’re all hoping to find.”
The U.S. research team reanalyzed the data using different methodologies that takes into account muscle activity and “the kind of randomness that EEG signals manifest over time,” states background material released with the study.
In an author’s response published in The Lancet, the Western University neuroscientists said that, while the new analysis suggests that two of the three “positive” vegetative patients didn’t always show awareness, corroborative data using functional MRI, a more powerful type of brain imaging, confirm that “these patients were aware during the same week in which the EEG data in question was acquired.”
When the Canadian team unveiled their cheap and portable method for test- ing patients presumed to be trapped in a permanent vegetative state in 2011, the findings were described as groundbreaking, even “astonishing.” The work was brought starkly back into the headlines in December, when the researchers reported they had tested Hassan Rasouli, the Toronto man at the centre of a landmark life support case.
Rasouli, 60, has been “without consciousness” since 2010, when he suffered complications from surgery to remove a brain tumour that left him with widespread brain damage, state court documents. His doctors want to withdraw life-support and administer palliative care. His family is fighting to keep him in the ICU indefinitely on a ventilator, saying that he has shown signs of awareness. The Supreme Court of Canada is now deliberating the case.
When Rasouli was tested by Adrian Owen, one of the coauthors of the original study published in the Lancet, the tests reportedly showed a “very low level” of consciousness.
For their study reported in the Lancet in 2011, Owen and co-author Damian Cruse, of Western’s Centre for Brain and Mind, compared 16 patients with a diagnosis of vegetative state with 12 healthy patients, or “controls.” They used an EEG, which measures electrical signals from neurons.
Patients were given basic commands to use in response to a series of questions. They were told to imagine squeezing their right hand to answer yes, and moving their toes to answer no.
Three of 16 patients responded to the commands, show their EEG responses, the authors reported. The findings, they said, showed their EEG method could identify “covert awareness” in seemingly vegetative patients.
But Weill Cornell Medical College researchers said they could find no evidence in the brain signals that the vegetative patients were actually responding to the commands, said Schiff, a leading authority on neurological disorders of consciousness.
The method of determining awareness and interpreting the EEG signal was flawed and would lead to false positive results, he said.