By the Blouin News Science & Health staff

Major study on consciousness in vegetative patients looks flawed

by in Research.

Doctors examine a MRI scan of a patient at the Gandhi Government General Hospital (RGGGH) in Chennai July 12, 2012

Doctors examine a MRI scan of a patient at the Gandhi Government General Hospital in India (REUTERS/Babu)

In 2011 the medical journal The Lancet published a study that claimed to detect brain activity in people previously thought to be in a vegetative state.  The results were widely reported, and if true, would have had profound consequences for the way doctors diagnose and treat people with severe brain injuries.  But a reanalysis of the data, published on Jan. 26,  has determined that the statistical analysis and methods used in the earlier study were flawed, essentially invalidating the groundbreaking conclusions.

The new report will likely disappoint many people holding out hope that their loved ones in vegetative states were misdiagnosed, but affirms the importance of the scientific process in assessing preliminary research, particularly concerning matters so personal and with momentous implications for clinical practice.

The 2011 study, lead by a team of researchers from the University of Western Ontario, used an EEG to measure the brain activity of vegetative patients, who were instructed to move either their hands or toes. The researchers then studied the EEG transmissions for activity in the prefrontal cortex – the area of the brain involved in orchestrating movement. They concluded that three of the 16 patients previously characterized as vegetative were responsive and capable of advanced cognitive activity.

The results of the study were picked up by many news outlets and hailed as a medical “breakthrough.” A number of articles described the patients as “buried alive” or “locked in their bodies,” and suggested that the findings could point the way towards communication with people in vegetative states in the future.

Before adopting the use of EEGs for diagnosing patients with “minimal consciousness” into clinical practice, however, the results would have to be replicated.

The recent reanalysis attempted to validate results of the earlier study, but showed that they were marred by a number of erroneous assumptions in methodology and analysis. Using data shared from the original researchers, a team of neurologists from Weill Cornell Medical College found that the study had failed to account for disturbances originating from outside the brain in the EEG signals, and did not control for the random EEG signals that occur over time, suggesting that the detected signals were no more than chance fluctuations in brain activity.

It is notoriously difficult to assess the precise level of brain activity in people in vegetative states, and people previously diagnosed as such have been found to exhibit “minimal consciousness” in certain situations when examined with an MRI machine.  But it is not feasible to investigate every brain-injured patient with an MRI — they are expensive and bulky — and so some so-called vegetative patients are presumably misdiagnosed.  Part of the reason the 2011 study was so welcome is that it provided a way to easily test brain-injured patients with a bedside EEG.  The EEG could even be used in the home to establish routine communication with people determined to be “minimally conscious” — a prospect that the researchers excitedly promoted.

Reanalysis and validation is an important part of the scientific process, but many researchers are hesitant to revisit old studies.  There is no glamour in proving someone else’s research to be valid, and journals are less inclined to publish substantiating reports over new research.  For similar reasons, media outlets are also less likely to report on the results of follow-up studies.  But for such an emotionally charged topic that likely stoked the hopes of many people desperate to communicate with their loved ones in vegetative states, it is important that this reanalysis is covered to the same extent as the original research, lest false hope and misinformation spread.

Years ago The Lancet published a widely circulated study that linked autism in children to the commonly administered MMR vaccine.  Even though the results have since been retracted, many people persist in believing in the association. Like the EEG study, over-hype is always a danger with such preliminary research, and scientists and journalists have a responsibility to communicate to the public that any discussion of the potential implications must be restrained.  Let’s hope that, for the sake of the friends and family of people in vegetative states who were eager about the prospect of communicating with them, the recent reanalysis gets the attention it deserves.