Brain imaging can reveal if people with comas or in vegetative states have retained their mental capacity to respond to ‘yes’-or-‘no’ questions, according to a study published today in JAMA Neurology.
Expanding upon similar landmark findings from 2010, this study also found that unconscious patients could pay attention to complex set of instructions. The results may change the way that doctors define consciousness.
The revelations were made by using functional magnetic resonance imaging (fMRI) in three patients with severe brain injuries. Two of the subjects were clinically defined as “minimally conscious”, while the other had been in a persistent vegetative state for nearly 12 years.
Terri Schiavo, whose case of brain injury triggered a fiery pro-life and power of attourney debate in the late 1990s, suffered from a persistent vegetative state.
Patients who are minimally conscious may exhibit simple behavioral reactions, such as smiling, reaching for objects, and making eye contact. In contrast, a vegetative state is defined by little-to-no structured behavior in response to the outside world.
While being scanned by an fMRI, the patients were asked to either follow a command — “keep a running tally of everytime you hear a specific word” — or they had to answer a series of yes-or-no questions about themselves — “Is your name Steve?”
All of the patients were able to follow commands. Only two of the patients could communicate ‘yes’ or ‘no’ — one in a minimally conscious state and the vegetative patient.
"To our knowledge, in this study we establish for the first time that some entirely behaviorally nonresponsive patients can use selective attention to communicate," the authors from Western University (Ontario, Canada) concluded. "Moreover, this technique assesses selective attention, a basic building block of human cognition, which underlies many complex faculties, including reasoning and, more broadly, information processing."
Source: Naci L, Owen AM. Making Every Word Count for Nonresponsive Patients. JAMA Neurology. 2013.