PEOPLE in a minimally conscious state have been“woken”, gaining the ability to communicate for a whole week after a brief period of brain stimulation.
The breakthrough suggests we may 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 cannot give any meaningful response), they are said to be in a vegetative state. If they show fluctuating signs of awareness but cannot communicate, they are described as minimally consciousness.
In 2014, Steven Laureys at the University of Liège in Belgium and his colleagues discovered that 13 people with minimal consciousness and two people in a vegetative state showed new signs of awareness when given mild electrical stimulation.
The people in the trial received transcranial direct current stimulation (tDCS), which applies low-level electrical stimulation via electrodes on the scalp to make neurons more or less likely to fire. This was targeted once over an area of the brain involved in consciousness.
Soon after, they showed signs of consciousness, including moving their eyes when instructed. Two people were even able to answer questions for 2 hours by moving their body, before drifting back into their previous state.
The team wondered if more stimulation would extend the duration of the effect. They began a new trial, in which 16 people received a 20-minute session of tDCS daily for five consecutive days, or a sham session, in which they received low-level 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 – making spontaneous recovery unlikely. After the fifth day of the real treatment, nine participants showed significant improvements in conscious awareness. This included being able to respond to commands, and perform voluntary 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,” says 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 unconscious. Thibaut says that as well as increasing activity in the immediate area, the tDCS also increased communication between other areas of the brain – potentially helping to propagate this wave of “conscious” activity.
“This is an encouraging development,”says John Whyte, director of the Moss Rehabilitation Research Institute in Pennsylvania. However, we don’t know how quickly the improvements from longer treatment will wear off, he says.
The team says that the results 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, so in theory the patient’s family could be taught how to use it at home.
Although there were no side effects in the recent trial, Thibaut says we first need to determine whether using the device for months on end is safe or effective.“We don’t know the long-term effects yet,” she says. “We need to see what happens when we use it for perhaps five hours a day, or if we apply it daily for three months. We need to be really careful.”