My father-in-law recently had brain surgery to remove a benign melingioma about the size of a lemon from right middle hemisphere of his brain. They have labeled the surgery a "success" and he is currently in inpatient rehab to help regain physical function, however he has become very mean and aggressive. He's even had hallucinations of people abusing him or is lying, we aren't sure which. Is this to be expected and if so is there any treatment available.