Doctors should resist the temptation to use an inexpensive tool that probes the brain's electrical activity when evaluating vegetative patients who can't communicate.

Drs. Adrian Owen and Damian Cruse of the Centre for Brain and Mind in London, Ont., promoted the use of electroencephalography or EEG that can be used at a patient's bedside to determine if there's neurological activity in people in a vegetative state — those who are unresponsive in traditional tests of awareness.

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Dr. Damian Cruse adjusts EEG sensors that his team uses to check for neurological activity in people thought to be in a vegetative state. (Courtesy UWO)

In a letter published in Thursday's issue of the medical journal The Lancet, Dr. Jonathan Victor of Weill Cornell Medical College in New York and his co-authors reanalyzed data shared from Owen's 2011 paper in the same journal.

"I think we'd be very, very cautious about using this technology as it stands now," said Victor.

Both groups agree the use of EEG technology remains promising to evaluate patients. The challenge, Victor said, is researchers can't be certain about their interpretations when faced with families trying to communicate with their loved ones, including for end-of-life discussions.

The critique casts doubt on the original statistical approach and assumptions, which didn't hold when analyzed with a different model.

In a rebuttal, Owen's team defended its approach as the only way to draw valid conclusions from vegetative patients and account for their variations.

"There are few 'known truths' when attempting to detect covert awareness," Owen's team wrote. "Some are likely to be truly vegetative, while others may appear to be vegetative behaviorally, but are in fact, covertly aware."

Ryan D'Arcy, a neuroscientist at Simon Fraser University and Surrey Memorial Hospital in Vancouver, is part of a team developing a similar device to detect consciousness.

For D'Arcy, the challenge is turning a laboratory procedure into a test that can be used on patients.

"You need to be able to convert the data which are very sophisticated and complex into a valid clinical score," D'Arcy said.

The teams' discrepancies could lead to vastly different approaches to caring for patients, anesthesiologists George Mashour of the University of Michigan, Ann Arbor, and Michael Avidan of Washington University said in a journal commentary.

The critique's authors "present a compelling argument that this claim of neurophysiological responsiveness has a questionable statistical basis, potentially undermining the interpretation of two studies by Cruse and colleagues," Mashour and Avidan wrote.

The pair commended the two teams for sharing their data and publicly debating the controversy.

Victor is working with Owen's team to figure out the best way of interpreting the signals.

With files from CBC's Kim Brunhuber and Pauline Dakin