I've had it too. Seems to be fading now, but every once in a while it'll really light me up. I found some info through the BDSSite.com websit run by Barry Sebastion, a fellow survivor (7 Years). Try this link to hs website's info on L'Hermiites sign:
http://www.bdssite.com/scc/lh.htm

Most of what I've read says it's relatively rare, occuring in 3 to 5 % of those who've received high doses of radiation to the cervical spinal chord, and all say it fades in 6 to 9 months. It's particularly disquieting for me, if you can imagine being an elecronics technician with your hands on a couple of test leads in an energized electrical panel. As you look down to see what the meter reads, you get a shock! It took me 3 attempts to figure out it was the L'Hermitte's and not the test equipment. Fun with side effects! )
Hope it's not bugging you too badly. Chances are good it will go away relatively quickly.

Good Health

Chuck