There have been cases of complete personality changes from traumatic brain injury documented before. It has been explained that it is the part of the brain that is damaged that causes the personality change. Aggressive behavior is governed by a different part of the brain from nuturing behavior.

There is also an unusual case of a British woman who now speaks with a French accent after a migraine attack.

http://www.msnbc.msn.com/id/39195151...-womens_health