I don't know whether to laugh or cry when I read these stories.  I find new symptoms that I have, that I never suspected had anything to do with the AC.
I was just diagnosed last month.  I think it is in the left posterior fossa, and have no idea how big it is.  The radiology report only said that is was a "normal arachnoid cyst".  I saw the neurologist, who started recommending larger doses of Ibuprofin.  So I said, "is there any cause to these headaches?" and he answered, "oh, you have an arachnoid cyst".  I could have kissed him right then and there.  I was so relieved to find out the cause of these stupid headaches.  I have had them for so long that I thought they were just a normal part of my hormonal cycle.
I am 47 years old. My eyesight on my left side has grown significantly weaker.  I have had irregular heartbeats that they can't diagnose, even to the point of being hooked to the heart monitor and having verifiable irregular heartbeats (feels like a caged squirrel in my chest), and the dr saying it's perfectly normal.  I asked him, "does that sound normal to you?"
I am so forgetful, it's my middle name.  I trained for a new job last year and was so frustrated at my inability to remember all of the new stuff I was supposed to be learning.  It took me forever.  I also lose everything.  I have to make notes all of the time.  I insert random words into sentences that make no sense whatsover.  (Honey, go put the keys in the refrigerator).  It makes for some good laughs.  I can only sleep for four or five hours at a time even when I am totally exhausted, and can't go back to sleep at all.  I have hearing loss, and screaming ringing in both ears, especially the left.   I also get dizzy very easily, like when I ride an elevator.  I just returned from a four day cruise, and it took two weeks for my head to stop spinning.  Thank God I don't get motion sickness.
The headaches have been the major symptom.  If I take Excedrin Migraine right at the onset, I can deal with them.  Ibuprofin just doesn't work.  They have been increasing over the past year.  They used to last two to four days right before my period.  Now they last up to two weeks.  I can function with them, though I feel like something has invaded my brain.  I worked for an ENT and told him that I feel like something is inside my brain behind my left sinus.  It was senstive to air when I breathed in, so I thought it was a sinus infection, but my sinuses were clear.  He's the one who referred me to the neurologist.
I actually made a OB/GYN appt because of my whacked-out emotions.  I am stressed all of the time, and feel so irritated and frustrated!  It's all I can do to make the appearance of being nice sometimes.  I just figured my hormones were wreaking havoc.  Yet I read so many of the stories where feelings of agitation are part of the symptoms of AC. 
I had a follow-up MRI done yesterday, and will meet with the neurologist again in two weeks.  Believe it or not, my first MRI was done one and a half years ago, and the two doctors who saw the report never bothered to tell me about the cyst. 
I read some of the other stories and know I don't have it nearly as bad as it could be.  I just can't believe that something growing or even existing in our brains could be considered normal.  Thanks to all of you who have written your stories.  The information we gain from each other will help us to continue to push for reasonable treatment.  Hopefully.