Delirium (confusion) after surgery is common and associated with a longer hospitl stay and increased hopsital cost. There is very little information available about how often delirium occurs and the complications associated with it. Elderly patients are at high risk for delirium after surgery. This research is being done to measure how often delirium after spine surgery occurs and to see if there are ways to predict if delirium will develop. The results from this study will provide important information on a possible mechanism and predictor of delirium.