I'm 29 years old and in September of 09' was diagnosed with a Cavernous Malformation (AVM) in my right frontal lube. I had it removed in January 10'. Two days ago I just found out the my 27 year old sister has a Arachnoid Cyst in her left frontal lube. ( We're still waiting to see what needs to be done with it.) I'm just wondering what the odds may be to two sister's having unrelated conditions with their Brain's with in a year of each other?