Eighteen months after the first scan, Wallis had improved even more -- he could move his previously paralyzed lower limbs, a recovery that was "as unexpected as him recovering speech," says Schiff. When the researchers imaged his brain a second time, they found that the unusual area in the back had normalized, while another region, in an area that regulates movement, seemed to have grown more connected. The findings were published this week in The Journal of Clinical Investigation.

The researchers theorize that the changes they saw in the brain images correspond to growth of new neuronal connections. This growth might spark the recovery of different functions, such as language and movement. "Why did he emerge? None of us can answer this," says Joy Hirsch, a neuroscientist at Columbia University who was not involved in the current study but collaborates with the researchers on other projects. "But it suggests a biological underpinning to recovery."

James Bernat, a neurologist at Dartmouth Medical School in Hanover, NH, cautions against drawing too broad a conclusion from Wallis's recovery: people tend to enter a minimally conscious state after suffering diffuse injury to the neural processes in the brain rather than massive death of the neural cells themselves, and such injuries may be easier to recover from. But he says the fact that Wallis's motor improvements correlate with a neural change in a brain area that controls movement is particularly exciting. "We need to find out how often it happens, and why it happens," says Bernat.

Of course, it's difficult in any case to extrapolate from this one extraordinary case. No one knows what Wallis's brain looked like before the accident or before he began to speak again. And it's unclear why these specific parts of the brain were able to regenerate, or how the particular patterns of growth helped Wallis recover. But the findings do emphasize how important it is to study minimally conscious patients. "I think this paper serves as a beacon -- it suggests there are mechanisms for emergence into consciousness, even if we don't understand them," says Hirsch. "This is a very hopeful sign for a field that has not received much attention from the medical and scientific world."

Laureys, who wrote a commentary accompanying the paper, adds that he hopes the findings will change the sense of hopelessness many doctors feel about minimally conscious or vegetative patients. Though doctors know that the brain can reorganize itself by forming new neural connections throughout life (a phenomenon called neuroplasticity), Laureys says they previously thought this process ran out of steam soon after an injury. But he hopes this case will make them reconsider. "After many years, there is still a lot of plasticity going on with very significant clinical consequences," he says.

Ultimately, doctors hope to find specific signs in the brain that predict which patients will get better. They also hope to develop targeted treatments that could help that process along. "But we can't answer those questions without proper control studies," says Hirsch.

The Cornell researchers now hope to study a larger number of people in the minimally conscious state to try to get a more systematic picture of the mechanisms underlying recovery.