[Fitzcarraldo]

Neurons do not grow back. The brain can rewire itself so that remaining healthy tissues take over functions that had been done by the cells that died. But if that were happening, it would have shown in Schiavo's behavior by now, said Dr. Michael T. Pulley, an assistant neurology professor at Shands Jacksonville Hospital, affiliated with the University of Florida medical school

This can be helped by therapy - something her husband denied her.

[Keeley Finn]

Well I don't know much about medicine, but wouldn't that be kind of like an arm growing back?

[Fred]

They can tell that to Terry Wallis and his family. Terry was in a coma for 19 years, his family has been caring for him all this time at their home. Terry is now speaking. The doctors have no ideas as to how he regained his ability to speak. They said he would never speak again. Terry's mother neve lost hope and said she knew he would get better.


Mind and Body
http://www.channel4.com/science/microsites/S/science/body/coma.html