Minimally conscious people woken for a week

People in a minimally conscious state have been “woken” for a whole week after a brief period of brain stimulation (New Scientist, 2017). The breakthrough suggests scientists might be on the verge of creating a device that can be used at home to help people with disorders of consciousness communicate with friends and family.

People with severe brain trauma can fall into a coma. If they begin to show signs of arousal but not awareness, they are said to be in a vegetative state. If they then show fluctuating signs of awareness but cannot communicate, they are described as being minimally consciousness.

In 2014, Steven Laureys at the University of Liège and his colleagues discovered that thirteen people with minimal consciousness and two people in a vegetative state could temporarily show new signs of awareness when given mild electrical stimulation.

The people in the trial received transcranial direct current stimulation (tDCS), which uses low-level electrical stimulation to make neurons more or less likely to fire. This was applied once over an area of the brain called the prefrontal cortex, which is involved in “higher” cognitive functions such as consciousness. Soon after, they showed signs of consciousness, including moving their hands or following instructions using their eyes. Two people were even able to answer questions for two hours by moving their body, before drifting back into their previous state.

Because the improvements in awareness lasted for only a few hours, the team wondered if more stimulation would extend this. They began a new trial, in which sixteen people with brain damage received a twenty minute session of tDCS daily for five consecutive days, or a sham session, in which they received a low level of stimulation that had no effect on the brain. Later, they received the opposite treatment.

Each participant had been in a minimally conscious state for at least three months before the start of the trial, meaning spontaneous recovery was unlikely. After the fifth day of the real treatment, nine of the sixteen participants showed significant improvements in conscious awareness. This included being able to respond to commands, recognise objects and perform voluntary motor movements. What’s more, these improvements lasted at least a week after the final day of stimulation.

Two of the participants even started to communicate. “They couldn’t speak but we could ask questions, such as “is your name David?” and they answered yes or no by moving a part of their body, like their tongue or their foot” said Aurore Thibaut, also at the University of Liège, who led the study. “They correctly answered all of the questions we asked.”

None of the participants showed any signs of improvement after the sham treatment.

The stimulation targeted the prefrontal cortex, which is involved in consciousness. It is also linked to other vital hubs, such as the thalamus, which helps propagate electrical signals to wider areas of the brain.

When a person is conscious, electrical activity spreads like a wave into brain areas that are never reached while someone is unconscious. Aurore Thibaut said as well as increasing activity in the immediate area, the stimulation also probably increased the communication between other areas of the brain, potentially helping to propagate this wave of “conscious” activity.

“This is an encouraging development” said John Whyte, director of the Moss Rehabilitation Research Institute in Elkins Park, Pennsylvania. “The study suggests that longer treatment intervals lead to more sustained improvements in consciousness.” However he said it was still unknown whether the improvements from longer treatment would wear off eventually.

The team said the results are starting to look clinically relevant, meaning they are good enough to consider how to use the technique to treat patients away from the hospital. The stimulation device can be used at the bedside, and is relatively cheap to produce, so in theory the patient’s family could be taught how to use it at home.

More trials will be needed before this happens, though. Although there were no side effects in the recent trial, Aurore Thibaut said it first needs to be determined whether using the device for months on end is safe or effective. She said “You can find similar devices online, but we don’t know the long-term effects yet. We need to see what happens when we use it for perhaps five hours a day, or what happens if we apply it daily for three months. We need to be really careful.”

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