Had bells palsy twice sent for MRI by ENT this is where they discovered a sub Arachnoid Cyst...saw private neurosurgeon who was a Professor he said he wouldn't touch me due to location & depth so sent me on my way ...like yourself I knew exactly where it was prior to been told what it was...headaches pulsating vision issues pressure where Cyst is ...if it bursts I've an hr to get hospital I've had Cyst on ovary that burst plus 1 inside finger bone that had to be scrapped out ..they are not sure whether I was born with it or it occurred after a bad accident ... I'm aware it's there & just get on with stuff ...UK I reside, there is a website Arachnoid Cyst plus Facebook have a group for people .