Well, hopefully it's not a prophetic dream. (have you had strange-bad headaches lately...stuff like that? if not, I wouldn't worry about that...) Most likely dreaming that means you've possibly been under a good bit of mental stress or have things you need to work out in your mind.
It is suggested that dreams are a way of processing and substantiating memory. Have you been questioning certain perspectives, certainly this question suggests it.
Dreams about the brain in general tend to be because of mental stress or needing to re-figure something out. Good luck!
