Fifteen years ago, a 20-year-old man in France suffered traumatic brain injury in a car collision and fell into a persistent state of unconsciousness known as a vegetative state. Now, a new study suggests that an experimental form of low-intensity nerve stimulation in the brain—now approved to treat depression and epilepsy—succeeded in stirring the man into a what physicians describe as a “minimally conscious” state. It’s a far cry from a total revival, but the study authors suggest that the findings hint at a major avenue of new research into restoring consciousness following brain injury.
Still, some physicians and brain injury specialists remain skeptical about whether the treatment truly worked as described. The surgery to implant the electrical stimulator, the frequent behavioral observations, and the moving in and out of brain scanners all could have contributed to the patient’s improved state, says Andrew Cole, a neurologist at Harvard Medical School in Boston who studies consciousness. “I’m not saying their claim is untrue,” he says. “I’m just saying it’s hard to interpret based on the results as presented.”
Hundreds of thousands of people live in a vegetative state. Though they don’t respond to stimuli such as touch, these individuals aren’t brain dead. Their brains often have recognizable sleep-wake cycles, they open their eyes and can swallow when feeding, and many spontaneously moan, cry, smile, and exhibit other signs of partial consciousness. Most experts consider any vegetative state that persists beyond 12 months to be permanent, however.
That assumption didn’t satisfy Angela Sirigu, a cognitive neuroscientist at the Institute for Cognitive Sciences–Marc Jeannerod in Lyon, France. She and a team of clinicians wanted to try a form of therapy known as vagus nerve stimulation (VNS) on the car crash victim. The treatment involves implanting a palm-sized, disk-shaped stimulator that gives off miniscule electrical shocks—less than a hundredth of the electrical current in a battery-powered wrist watch—to the vagus nerve, a critical brain signal superhighway that delivers information from the brain stem to the heart, esophagus, lungs, digestive tract, and other parts of the body.
Such nerve stimulation has been explored as a therapy for a wide range of disorders such as epilepsy, depression, arthritis, and cluster headaches, although it’s unclear exactly why it works. Sirigu had a hunch it might help people in a vegetative state because the vagus nerve connects to the thalamus, a deep-seated brain region linked to consciousness and awareness. Electrically stimulating the thalamus can temporarily rouse a person in a minimally conscious state, and Sirigu wondered what would happen if she stimulated it for long periods of time.
She and her team implanted a vagus nerve stimulator in the crash victim’s chest, then continuously stimulated the nerve. They regularly monitored the man’s response to voice commands, his ability to track an object with his eyes, and his brain activity.
After a month, the man showed subtle signs that he could interact with the world, albeit in extremely limited ways. He regained the ability to follow an object with his eyes and he could turn his head on request. He appeared startled when a physician quickly thrust her face in front of his. And brain metabolism—a proxy for neuronal activity—increased in several regions of the brain. Perhaps most tellingly, says Sirigu, the man’s brain began producing stronger theta waves, electrical brain rhythms correlated with consciousness.
The researchers continued to track the man’s progress while he received constant nerve stimulation. Nine months later, his level of consciousness didn’t continue to improve, but it didn’t slide back into a vegetative state, either. The findings raise hopes that even brain injury patients who’ve been in a vegetative state for years can regain some basic level of consciousness, the team reports today in Current Biology.
Achieving even minimal consciousness may be cause for celebration for families, Sirigu says, although she recognizes that asking them to subject their loved ones to experimental, potentially dangerous, treatments can be a risky proposition. “We are very thankful to this patient and his family,” she says. “They demonstrated a lot of courage.”
Why might electrical stimulation spur consciousness? One possibility is that after this patient’s injury, his thalamus was still trying to talk to the other parts of the brain, but broken connections were dampening its signal too much for it to be heard, Sirigu explains. The VNS effectively turned up the thalamus’s volume, allowing more signal to get through and enabling the brain to detect and respond to stimuli once again.
Neuroscientist Nicholas Schiff of Weill Cornell Medicine in New York City agrees with Cole that a study of a single patient is not enough to make sweeping conclusions about the therapy, but he is optimistic about the treatment’s promise. Researchers now need to treat multiple patients with VNS under a variety of stimulation durations and strengths, he says, which is incredibly expensive and time-intensive. Insurance companies will cover rehabilitative care, but convincing them that someone in a vegetative state can be rehabilitated—or that a minor improvement in consciousness counts as rehabilitation—has been an uphill battle, Schiff argues.
“One of my colleagues recently described [the plight of people in a vegetative state] as a civil rights issue,” Schiff says. “We need to make this area of medicine look like every other. The scientific advances here remain way ahead of the infrastructure.”