1. From the Neurology Unit (M.M.G.), Hospital Álvarez-Buylla, Mieres, Oviedo, Spain; the Neurology Department (P.O.N.), Hospital Universitario Central de Asturias, Celestino Villamil, Asturias, Oviedo, Spain; and the Radiology Department (A.A.C.), Hospital Universitario Central de Asturias, Celestino Villamil, Asturias, Oviedo, Spain.