27th September 2017
After 15 years in a vegetative state, nerve implant restores consciousness
A 35-year-old man who had been in a vegetative state for 15 years after a car accident is reported to have shown signs of consciousness after neurosurgeons implanted a vagus nerve stimulator into his chest.
A 35-year-old man who had been in a persistent vegetative state (PVS) for 15 years after a car accident has shown signs of consciousness after neurosurgeons implanted a vagus nerve stimulator into his chest. This outcome challenges the general belief that disorders of consciousness persisting longer than 12 months are irreversible, the researchers say.
Their findings, reported this week in Current Biology, show that vagus nerve stimulation (VNS) – a treatment already in use for epilepsy and depression – can help to restore consciousness even after many years in a vegetative state.
By stimulating the vagus nerve, "it is possible to improve a patient's presence in the world," says Prof. Angela Sirigu, at the Institute of Cognitive Science in Lyon, France.
The vagus nerve connects the brain to many other parts of the body. It is the longest nerve of the autonomic nervous system in the human body and is known to be important in waking, alertness, and other essential functions. To test the ability of VNS to restore consciousness, the researchers wanted to select a difficult case, to ensure that any improvements could not be explained by chance. They chose a patient who had been lying in a vegetative state for more than a decade with no sign of improvement.
Credit: Cyberonics, Inc./LivaNova
After one month of vagal nerve stimulation, the man's brain activity significantly improved. Following many years in a vegetative state, he had entered a state of minimal consciousness. The man began responding to simple orders that had been impossible before. For example, he could follow an object with his eyes and turn his head when requested. His mother reported an improved ability to stay awake when listening to his therapist reading a book. The researchers also observed responses to "threat" that had been absent before. For instance, when the examiner's head suddenly approached the patient's face, he reacted with surprise by opening his eyes wide.
Recordings of brain activity also revealed major changes. A theta EEG signal important for distinguishing between a vegetative and minimally conscious state increased significantly in areas of the brain involved in movement, sensation and awareness. VNS also increased the brain's functional connectivity. A PET scan showed increases in metabolic activity in both cortical and subcortical regions of the brain, too.
These findings prove that the right intervention can yield changes in consciousness "even in the most severe clinical cases", the researchers say.
"Brain plasticity and brain repair are still possible even when hope seems to have vanished," Prof. Sirigu says.
The researchers are now planning a large collaborative study to confirm and extend the therapeutic potential of VNS for patients in a vegetative or minimally conscious state. In addition to helping patients, Sirigu says the findings will also advance understanding of "this fascinating capacity of our mind to produce conscious experience."
Credit: Corazzol et al.
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