[1] Kennedy Krieger Inst, Dept Neurol & Dev Med, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sch Med, Dept Neurol, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ Hosp, Dept Radiol, Baltimore, MD 21287 USA
[4] Univ Texas SW Med Ctr Dallas, Dept Pediat Neurol, Dallas, TX 75390 USA