Vagus Nerve Stimulation Can Restore Consciousness

Neuroscientists in France have identified that vagus nerve stimulation (VNS) can restore consciousness even after someone has been in a vegetative state for over a decade. "This outcome challenges the general belief that disorders of consciousness that persist for longer than 12 months are irreversible," the researchers stated. This study, "Restoring Consciousness with Vagus Nerve Stimulation," was published on September 25, 2017, in the journal Current Biology.

Since 1997, VNS has been used as an adjunct therapy to treat pharmaco-resistant epilepsy and other maladies such as clinical depression, systemic inflammation, rheumatoid arthritis, migraine headaches, etc. As far as I know, this groundbreaking study on consciousness signifies the first time clinicians have utilized a VNS device to treat someone in a vegetative state.

To rigorously test the ability of VNS to restore human consciousness, the French researchers purposely enlisted a patient who had been in a vegetative state for 15 years to guarantee that any improvements couldn't be viewed as coincidental.

In this case, a 35-year-old man suffered a severe traumatic brain injury (TBI) in a car accident and was diagnosed as being in a vegetative state upon admission to the hospital. Over a decade later, when neurosurgeons implanted a small vagus nerve stimulator, he regained signs of consciousness as marked by improved behavioral responsiveness and enhanced brain connectivity patterns.

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The authors explain these dynamics in their paper: "Patients lying in a vegetative state present severe impairments of consciousness. There is agreement that this condition may involve disconnections in long-range corticocortical and thalamocortical pathways. Hence, in the vegetative state cortical activity is ‘deafferented’ from subcortical modulation and/or principally disrupted between the frontoparietal region. Some patients in a vegetative state recover while others persistently remain in such a state. The neural signature of spontaneous recovery is linked to increased thalamocortical activity and improved frontoparietal functional connectivity.”

Notably, VNS increased functional connectivity between multiple brain areas and a PET scan revealed increases in metabolic activity in both cortical and subcortical regions of the brain.

In a statement, Angela Sirigu of the Institute of Cognitive Sciences (ICS) in Lyon, France, who was the senior author of this study, said: "By stimulating the vagus nerve, we show that it is possible to improve a patient's presence in the world."

After just four weeks of VNS, the patient's attention, movements, and brain activity significantly improved. Researchers and family members began to observe that the victim of this devastating accident could respond to simple commands for the first time in 15 years. As an example, after one month of VNS, the patient could follow an object with his eyes and turn his head upon request. His mother reported that her son could also keep his eyes open and had the ability to stay awake when listening to someone reading a book.

Post-VNS therapy, the researchers also observed a knee-jerk reaction in response to a startling stimulus that was previously absent. For instance, when a doctor examining the patient made a sudden body movement, the patient opened his eyes widely and reacted with surprise. This suggests that he had entered a state of minimal consciousness.

“These findings show that vagus nerve stimulation can yield changes in consciousness even in the most severe clinical cases,” the researchers said in a statement. "Brain plasticity and brain repair are still possible even when hope seems to have vanished," Sirigu added.

As the authors describe in their paper: "These findings show that stimulation of the vagus nerve promoted the spread of cortical signals and caused an increase of metabolic activity leading to behavioral improvement as measured with the CRS-R scale and as reported by clinicians and family members. Thus, potentiating vagus nerve inputs to the brain helps to restore consciousness even after many years of being in a vegetative state, thus challenging the belief that disorders of consciousness persisting after 12 months are irreversible.”

​Vagus means "wandering" in Latin. The vagus nerve is referred to as the "wandering nerve" because it is the longest nerve in the human body and has multiple branches that begin in the brainstem and take a circuitous route to the lowest viscera of the intestines touching (and influencing) just about every major organ along the way.

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Your vagus nerve facilitates a constant psychophysiological dialogue between your mind, brain, and the milieu intérieur (environment within) of your body. The vagus is also commander-in-chief of the inhibitory parasympathetic nervous system which counterbalances excitatory "fight-or-flight" stress responses to maintain homeostasis. (To read more on this topic, check out “Vagus Nerve Survival Guide to Combat Fight-or-Flight Urges.”)

The vagus nerve is central to the bidirectional "gut-brain axis" feedback loop. After observing their patient who had been in a vegetative state restore consciousness post-VNS therapy, the researchers concluded: “Since the vagus nerve has bidirectional control over the brain and the body, reactivation of sensory/visceral afferents might have enhanced brain activity within a body/brain closed-loop process. Our study demonstrates the therapeutic potential of vagus nerve stimulation to modulate large-scale human brain activity and alleviate disorders of consciousness.”

In the near future, Sirigu's team will conduct a bigger collaborative study to confirm and extend the therapeutic potential of VNS for patients in a minimally conscious or vegetative state. In addition to helping patients, Angela Sirigu is excited that these findings also help to advance our understanding of what she describes as "this fascinating capacity of our mind to produce conscious experience."