1. From the Departments of Neurology (R.L.B.-M., D.C.A.), Radiology (S.T.), and Medicine (K.M.W.), Hennepin County Medical Center, and the Departments of Neurology (R.L.B.-M., H.B.C., D.C.A.) and Laboratory Medicine and Pathology (H.B.C.), University of Minnesota Medical School, Minneapolis.