From the Departments of Neurology (K.T.K., D.C., G.L.B., J.E.B., S.P., J.C., Y.S., S.A.M) and Neurosurgery (E.S.C., S.A.M.), College of Physicians and Surgeons, the Gertrude H. Sergievsky Center (Y.S.), and the School of Public Health (Y.E.D.), Columbia University, New York, NY. (At 2002-01)