I'd like to talk with other people who have chiari malformations.  is there a support group?

ACM group. You may contact the world acm group for support www.Familyvillage.Wisc.Edu/lib_arnd.Htm or wi chiari institute www.Wichiaricenter.Org/.
Web search. Try this site. http://www.dailystrength.org/c/arnold-chiari-malformation/support-group.