Cerebral injury will be determined in four ways. First, all patients will be evaluated using a battery of neuropsychometric tests before and after surgery. Patients admitted to the Irving Clinical Research Center (CRC) will have their tests one day before, one day after surgery and at 1 month. Those coming into the hospital on the day of surgery, "Same Day", will be evaluated on the day of surgery, one day after and at the 1 month follow up. Preoperative neurological and neuropsychological evaluation will be performed. The neuropsychometric tests are not intended to be diagnostic of specific neuropsychiatric disorders, but rather are designed to demonstrate general neuropsychological pathology. These tests can be divided into four types: (1) an evaluation of language, (2) an evaluation of speed of mental processing, (3) an evaluation of ability to learn using a list of words, and (4) an evaluation of visual perception requiring a patient to copy a complex figure. Before the battery is administered we will assess each patient's level of pain while sitting and standing using a 10 point Visual Analog Scale and then gauge their mood with a series called the Wong/Baker Faces Rating scale.