In a the interpretation of dreams in Islam, a brain represents savings. Having an oversized brain in a dream means reason. Having no brain in a dream means ignorance. Eating from one's own brain or the marrows of one's own bones in a dream means suspicious dealing with one's own money.
Eating someone else's brain in a dream means that one may die shortly or that he may steal someone's savings. A brain in a dream also may indicate one's beliefs, religious life and the work of one's innermost being. The dream of the brain is not important in itself, because it must always be combined with other elements of the dream. Also, don't forget to read the interpretation about the différent parts of body in dream.