After spending 15 years in a vegetative state following a car accident, a 35-year-old man fitted with a nerve stimulator in his chest has shown signs of consciousness. The findings, reported today in Current Biology, suggest that vagus nerve stimulation (VNS)—already used to treat epilepsy and depression—could help to restore minimal consciousness even in patients who've spent years in a vegetative state.
Known as a "pacemaker for the brain," a VNS device consists of a battery surgically installed under the skin in the chest, with a wire running up to the vagus nerve in the neck. The vagus nerve connects the brain to many other parts of the body and is involved in many essential functions, including waking and alertness. The VNS implant electrically stimulates the nerve at programmed intervals, in much the same way a pacemaker helps maintain a regular heart rhythm. The electrical signals can be adjusted to treat specific ailments; epileptics who perceive "auras" before a seizure can even place a magnet over the device to trigger a burst of stimulation.
Researchers wondered whether such treatment could help people in a vegetative state regain consciousness. The general belief is that after about one year, such unconsciousness is irreversible. Selecting a patient who'd been in a vegetative state for more than a decade, then, eliminated the possibility that any improvements were simply a coincidence and not the result of stimulation.
After about a month of stimulation, they saw significant improvement in the man's attention and movements. He could respond to commands that had previously been impossible, like following an object with his eyes and turning his head when asked (though that took about a minute to do). His mother said he was better at staying awake while his therapist read to him and he showed recovered responses to a "threat"—when an examiner's head suddenly approached the man's face, his eyes widened in surprise. He shed a tear when his caregivers played his favorite music.
These are signs of minimal consciousness, a marked improvement over a vegetative state. Brain scans also showed greater activity in the areas of the brain associated with movement, sensation, and awareness. The man's brain had greater functional connectivity (how different regions of the brain work with one another), and increased metabolic activity in the cortical and subcortical regions.
This figure shows information sharing across all electrodes before and after vagus nerve stimulation (VNS). On the right, the warmer colors (yellow/orange) indicate an increase of connectivity among posterior parietal regions.
Credit: Corazzol et al., Current Biology
After nine months of constant nerve stimulation, his level of consciousness plateaued. Though the man still can't talk or walk, researchers say his progress suggests that even people who've long been in vegetative states may respond to the right kind of medical intervention. In short, the brain may be more resilient than we've previously realized. "Brain plasticity and brain repair are still possible even when hope seems to have vanished," study co-author Angela Sirigu, a neuroscientist at Institut des Sciences Cognitives Marc Jeannerod in Lyon, France, said in a statement.
The next step will be to confirm and extend the results with more patients in both vegetative and minimally conscious states. If successful, the work won't only extend the usefulness of VNS treatment and offer hope to those in a long-term vegetative state. It may also, as Sirigu points out, help us better understand "this fascinating capacity of our mind to produce conscious experience."
Still, the research raises ethical questions, like whether people in a vegetative state would want to be aware of their condition and if doctors should withdraw care after 12 months if there's a possibility of restoring consciousness.
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