(NaturalNews) Researchers from the University of Liege, Belgium, have discovered that a high-tech brain scan may be able to predict which brain-injured patients who appear to be in a vegetative state have the best chance of eventually regaining consciousness, according to a study published in The Lancet on April 15.
"Our findings suggest that PET imaging can reveal cognitive processes that aren't visible through traditional bedside tests," lead researcher Steven Laureys said, "and could substantially complement standard behavioural assessments to identify unresponsive or 'vegetative' patients who have the potential for long-term recovery."
Current test unreliable
Doctors traditionally distinguish between comatose patients who are in a minimally conscious state (MCS) and those suffering from unresponsive wakefulness syndrome (a vegetative state). In an MCS, a patient still responds to some stimuli and shows some evidence of awareness; in a vegetative state, the patient is completely unresponsive and the chance of recovery has typically been considered very low.
To distinguish between these two state, doctors rely on a standardized test called the coma recovery scale-revised (CSR-R). Unfortunately, CSR-R is only accurate about 60 percent of the time.
"In patients with substantial cerebral oedema [swelling of the brain], prediction of outcome on the basis of standard clinical examination and structural brain imaging is probably little better than flipping a coin," wrote Jamie Sleigh from the University of Auckland, New Zealand, and Catherine Warnaby from the University of Oxford in an accompanying commentary.
For the study, the researchers compared two separate, 3D diagnostic brain scan tools: a positron emission tomography (PET) scanner and a functional magnetic resonance imaging (fMRI) scanner. The PET scan functions by mapping the progress of a radioactive tracer (attached to glucose, the brain's energy source) through the blood as separate brain regions are activated by a stimulus. The fMRI scan functions by detecting the uptake of oxygen in various brain regions in response to a stimulus.
Over the course of four years, the researchers performed PET and fMRI tests on 81 patients who had been diagnosed via CSR-R as being in an MCS and 41 who had been diagnosed as being in a vegetative state. The tests were also performed, for comparison purposes, on 39 healthy people and four with "locked-in" syndrome (in which the brain is fully active but the person is unable to respond behaviorally).
The researchers found that the PET scan was 93 percent successful at detecting MCS, while the fMRI was only 45 percent successful. In addition, the PET test was more effective than CSR-R in predicting eventual recovery.
According to the CSR-R, 36 patients were completely unresponsive. However, the PET scan found brain activity consistent with MCS in 12 of these patients, nine of whom eventually recovered.
"PET imaging can reveal cognitive processes that aren't visible through traditional bedside tests," Laureys said.
The findings could significantly improve doctors' ability to determine the likelihood of patient recovery.
"This study is welcome because diagnosis and prognostic accuracy in patients with severe brain injury needs to be improved," Sleigh and Warnaby wrote. "For example, intensive care doctors caring for former racing driver Michael Schumacher after his recent serious brain injury refused to offer any firm prognosis to the world's media."
PET scanning could have implications for patients' families, as well.
"If the results of this study are confirmed in future research, this could have far-reaching clinical, ethical and legal implications," said Michael Bloomfield of the Medical Research Council, who was not involved in the study, " including whether to offer an apparently unconscious patient pain relief and, ultimately, whether treatments that may be keeping someone alive should be continued or not."