3. Severe dementia or neurodegenerative disease, defined as either impairment that prevents the patient from living independently at baseline or IQCODE >4.5, measured using a patient's qualified surrogate, mental illness requiring long-term institutionalization, acquired or congenital mental retardation, Parkinson's disease, Huntington's disease, and/or coma or another severe deficit due to structural brain disease such as stroke, intracranial hemorrhage, cranial trauma, intracranial malignancy, anoxic brain injury, or cerebral edema.