1. From the Department of Neurological Surgery (V.S.B., T.Y.E.A., S.G.A., A.R.P., K.A.L., C.E., J.B., C.M.M., B.G.W., D.S., H.H.B., J.W.), University of Texas Southwestern Medical Center, Dallas.
2. Department of Radiology (C.M.M., B.G.W.), University of Texas Southwestern Medical Center, Dallas.
3. Department of Clinical Sciences (J.R.), University of Texas Southwestern Medical Center, Dallas.