Some good news for a change.
Please read this scientific article which was published just a few months ago.
I should point out that for some reason the link does always make a connection (maybe the local server is busy)? If you find this is the case then do try again.
http://icvts.ctsnetjournals.org/cgi/rap ... 7744v1.pdf
Also see this Wikipedia entry on nerve tubes, guide, conduits:
http://en.wikipedia.org/wiki/Nerve_guidance_conduit