1. From the Departments of Clinical Neurosciences (R.D.B., B.I.T., R.J.S., G.K., B.J.C.), Radiology (R.J.S.), Pathology (G.K., B.J.C.), and the Division of Neurosurgery (R.D.B., B.I.T.), University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.