I did a forum search for "arachnoid cyst" and found most of the discussion on these to be in the Traumatic Brain Injury forum.
Here's the shortcut link to get you there:
http://neurotalk.psychcentral.com/fo...aysprune=&f=92

When you are at the forum, use the 'forum search' feature at the very top/right side of the screen. Type in 'arachnoid cyst' and posts will come up of previous discussions.
Also you might want to start a thread there and you should get good feedback

Hope this helps
Rae