I don't think it would be a good idea. I have problems with both my neck and back and I do go to a Chiropractor, for my back. He's great and he's helped, but I would never let him touch my neck, even if I hadn't had prior surgeries. It's just not worth the chance, in my opinion, that something might go wrong, seizures, etc
I'm surprised Selma hasn't responded to your post. She's the one that would know.
Here's a link to her forum:
http://www.medhelp.org/forums/Chiari-Malformation/show/257