Ontario Researchers Find Signs of Consciousness in Unresponsive Brain-Injured Patient

SquareMotion/Shutterstock

Unresponsive patients with severe brain injury may still be conscious despite showing no signs of awareness at the bedside, a recent study suggests.

A brain-injured patient who was acutely unresponsive could control his mental activity when instructed to imagine playing tennis, researchers from London, Ont., reported in an Aug. 25 study published in the Proceedings of the National Academy of Sciences journal.

The findings could impact decisions on patient care, said the authors, which are typically based on subjective behavioural responses.

“These findings have important practical and ethical implications for the patient’s standard of care and quality of life,” reads the conclusion of the study, led by Canadians Karnig Kazazian and Androu Abdalmalak from Western University in London.

Researchers used a device to detect conscious processing in the brain. They tested three severely brain-injured ICU patients—one in a coma, another in a minimally conscious state (termed MCS), and another in a vegetative state—on their ability to process language and imagine themselves performing a movement.

Neural Responses

The MCS patient was tested on Day 15 of ICU stay. Patients in this state can typically control eye movement, reach for objects, and react to unpleasant stimuli. The researchers found the patient could passively perceive speech. The patient showed no language expression or ability to imagine movements.

The patient in the vegetative state, tested on Day 7 of ICU stay, showed the most robust responses, wrote the authors. They observed that the patient could “willfully” control his brain activity when told to do so.

“A successful motor imagery response reflects intention and does not occur in the absence of conscious awareness, suggesting that this patient’s true condition was cognitive motor dissociation,” they wrote. Cognitive motor dissociation is when patients are aware but can’t react to commands.

Researchers also found the patient could slightly process speech.

The patient in a coma, who was tested on Day 2 of ICU stay, did not show any response to the tests.

Neuroimaging has shown that 15 to 20 percent of patients clinically diagnosed as being in a vegetative state (also known as unresponsive wakefulness syndrome) are actually aware, despite not showing observable signs, says the study.

Brain Imaging Method

The technique used by the researchers is known as functional near-infrared spectroscopy (fNIRS), an optical imaging method for measuring neuronal activity that, according to the authors, has fewer limitations than other brain imaging methods such as functional magnetic resonance imaging (fMRI) and electroencephalogram (EEG).

“Our findings suggest that fNIRS is a viable tool for improving diagnosis and prognosis in patients with acute brain injuries in the ICU,” they wrote, adding that studies with larger sample sizes are needed to fully understand the prognostic potential of fNIRS.

They said their findings may open the door to the possibility of communicating with unresponsive patients in the future.