Evil is an act, not an appetite. How many haven't wanted to slash the throat of some boor across the dining room table? Present company excepted of course. Everyone has the appetite. If you give in to it, it, that act is evil. The appetite is normal.
As many know, brain injury comes in many forms. The two most prevalent brain injuries - stroke and trauma - affect more than 2. 2 million Americans, and these numbers are expected to grow.