1 Mallinckrodt Institute of Radiology (S.R.M., S.M.P., T.G.G., C.M.S., D.Y., K.T.K., J.P.C., A.T.E.), Washington University School of Medicine, St. Louis, MO.
2 Department of Neurology (J.K., K.P.G., C.D.S.), Washington University School of Medicine, St. Louis, MO.
3 Department of Pediatrics (A.S.S.), Washington University School of Medicine, St. Louis, MO.