Also found info at Stanford Department of Neurosurgery and The Cleveland Clinic which are a long way away, but they might be able to suggest someone in your area as well. Not sure if they work that way, but one would hope they would try.

http://cgi.stanford.edu/dept/neurosu...=arachnoidcyst
http://cms.clevelandclinic.org/neuroscience/

I checked out the Hydrocephalus and Tarlov Cyst forums just in case there was some info. in there as well. One user in Hydrocephalus I think it was, recommended a Dr Peter Black and when I looked up his info., I notice that there are a couple of email addresses posted there. One is his personal one and the other for patient matters to his clinical office. If you continue to have difficulty finding someone for your specific case, I'd email some of these other well known specialists and see if they can recommend someone in your area.

Boston Neurological Foundation http://www.boston-neurosurg.org/faculty/black.html

All the best.