[1] Johns Hopkins Univ Hosp, Dept Neurol, Baltimore, MD 21287 USA
[2] Johns Hopkins Univ Hosp, Dept Anesthesiol, Baltimore, MD 21287 USA
[3] Johns Hopkins Univ Hosp, Dept Crit Care Med, Baltimore, MD 21287 USA
[4] Johns Hopkins Univ Hosp, Dept Neurosurg, Baltimore, MD 21287 USA
[5] Henry Ford Hosp, Dept Neurol, Detroit, MI 48202 USA