[1] Vet Affairs Med Ctr, Augusta, GA 30904 USA
[2] Med Coll Georgia, Dept Neurol, Augusta, GA 30912 USA
[3] Seaman Family MR Res Ctr, Calgary, AB, Canada
[4] Univ Texas, Sch Med, Dept Neurol, Houston, TX USA
[5] Yale Univ, Sch Med, Dept Neurol, New Haven, CT 06510 USA
[6] Vet Affairs Med Ctr, New Haven, CT USA