FRIDAY, Feb. 25 (HealthDay News) -- Current methods of assessing higher-level functioning in severely brain-injured patients may be inadequate, researchers report.

The team at Weill Cornell Medical College used functional MRI, which tracks brain activity in real time, to assess how the brains of six patients responded to a set of commands and questions. The patients' conditions ranged from minimally conscious to locked-in syndrome, which means being fully conscious but unable to move or communicate, except through eye movements or blinking.

There was a wide and largely unpredictable variation in the patients' ability to respond to a simple command (such as "imagine swimming -- now stop") and then using that same command to answer simple yes/no or multiple choice questions.

Among patients unable to communicate by gesture or voice, some couldn't do the mental tests while others were intermittently able to respond using mental imagery. And some patients with the ability to communicate through gestures or voice were unable to perform the mental tasks.

The findings suggest that no current exam can accurately gauge the higher-level functioning that seems to be occurring in some severely brain-injured patients, said the researchers.

The study appears online Feb. 25 in the journal Brain.

"We have to abandon the idea that we can rely on a bedside exam in our assessment of some severe brain injuries. These results demonstrate that patients who show very limited responses at the bedside may have higher cognitive function revealed through fMRI," co-author Dr. Nicholas D. Schiff, a professor of neurology and neuroscience and of public health, said in a New York-Presbyterian Hospital/Weill Cornell Medical Center news release.

"Thousands of people suffer debilitating brain injuries every year, and there is a clear ethical imperative to learn as much as possible about their ability to communicate," study author Jonathan Bardin, a third-year neuroscience graduate student, said in the news release.

"These findings caution us against giving too much weight to negative results and open our eyes to the diversity of responses one might expect from the wide-ranging group of severely brain-injured people," he added.

More information

The Brain Injury Association of America has more about brain injury.