1. From the Departments of Radiology (C.W.F., A.B., E.K.S., O.S., A. Rai, A.Z.M.), Neurology (C.T.), and Surgery (T.B.), Boston Medical Center, 820 Harrison Ave, FGH Building, 3rd Floor, Boston, MA 02118; and Departments of Radiology (C.W.F., A.B., E.K.S., O.S., M.P., H.B., A. Rai, D.A., H.K., A. Ravilla, A.Z.M.), Neurology (C.T.), and Surgery (T.B.), Boston University School of Medicine, Boston, Mass.