1. From the Department of Neurology (L.C.J.), Johns Hopkins University School of Medicine, Baltimore, Md; the Departments of Neurology (Y.W.W., S.C.J., H.J.F.), Pediatrics (Y.W.W., H.J.F.), and Epidemiology (S.C.J.), University of California, San Francisco, Calif; and the Division of Research (S.S.), Kaiser Permanente Medical Care Program, Oakland, Calif.