[1] Johns Hopkins Med, Dept Neurol, Baltimore, MD 21287 USA
[2] Johns Hopkins Med, Dept Med, Baltimore, MD 21287 USA
[3] Univ Rochester, Med Ctr, Dept Neurol, New York, NY USA
[4] Univ Rochester, Med Ctr, Dept Biostat & Computat Biol, New York, NY USA
[5] Univ Rochester, William E Simon Grad Sch Business Adm, New York, NY USA
[6] Univ Rochester, Sch Med & Dent, New York, NY USA