1. From the Department of Radiology (W.B., H.J.C., D.F.K.), Department of Neurosurgery (W.B., D.F.K.), Department of Anesthesia (J.P., T.L.W.), Division of Preventive Medicine (M.H.M.), Knowledge and Evaluation Research Unit (M.H.M.), and Department of Neurology (A.A.R.), Mayo Clinic, Rochester, MN.