A 20-year-old man from France fifteen years back met with a car accident and suffered damage to his brain putting him is a vegetative state or a state where from he never regained consciousness. Now he is 35 years and an experimental low-intensity nerve stimulation method has been found to stir him into a “minimally conscious state”. Although he is not completely awake, there is hope that after similar brain injury the brain may be revived.
In this new study published in Current Biology, the team of researchers including Angela Sirigu, a cognitive neuroscientist at the Institute for Cognitive Sciences–Marc Jeannerod in Lyon, France and her colleagues, tried vagus nerve stimulation (VNS) on the patient. They surgically implanted a disk-shaped palm-sized electrical stimulator to the vagus nerve that gives off minute electrical shocks. These shocks are less than one hundredth of the current required to run a battery-powered wrist watch. The vagus is one of the most important nuerves in the body that carries signals to major organs such as the brain, heart, lungs, gut, digestive system as well as other parts of the body.
As Sirigu explained, nerve stimulation has been studied for brain damage for a while now. It has been tried for other brain diseases as well including epilepsy, cluster headaches, Parkinson’s disease, dementia etc. It is not clear why these work. However, Sirigu says that it could be beacue the vagus nerve connects to the thalamus. Thalamus is a deep-seated region of the brain that leads to awareness and consciousness. If this thalamus is stimulated, it could lead to consciousness. If temporary stimulation leads to rousing a person, long term stimulation of the thalamus could lead to waking up of a vegetative person she speculated. This was the hypothesis the team had worked upon.
For this study the team thus implanted a vagus nerve stimulator in the chest of the patient and kept stimulating the vagus nerve. They then closely monitored his brain activity and also if he could respond to voice commands or track objects with his eyes. The currents provided were small and they passed through the vagus nerve to the brain stem or base of the brain to different parts of the body.
A month into the therapy the man showed small signals that he was more interactive with the world. He started to respond. He was still deemed “minimally conscious” but was still improving from his previous vegetative state say the researchers. For example, the person now could track an object with his eyes and also turn his head when requested. There was a startle response when he was faced with another face close to his suddenly. Brain mapping of activities showed that metabolism was better in the brain in certain regions. This means that these regions were working better now. The brain was also producing stronger theta waves explained Sirigu. These waves are patterns seen on EEG or electroencephalogram and are connected to consciousness.
The persons’ progress is being continuously monitored. After around nine months of the stimulation therapy, although he remained static at his level of consciousness, he did not deteriorate either. This raises hopes for others in this state too says the team. However, experts warn it may be too early to speculate similar successes or more in other patients. A single case might not be indicative of others. But this experiment shows promise they agree.