Note: I notice that the link I posted on this old thread is no longer valid but it's too old for me to edit.
Just having a quick search, I imagine the same info can be found at the link below...

ScienceDaily, 26 October 2009. Master Regulator Found For Regenerating Nerve Fibers In Live Animals -- ScienceDaily.

'Summary:Researchers have found an essential factor for regenerating neurons in the central nervous system, which normally can't regenerate. This enzyme, or factors that stimulate it, could lead to a possible treatment for stroke, spinal cord damage and traumatic brain injury."