[1] Univ Pittsburgh, Dept Neurol Surg, Med Ctr, Pittsburgh, PA 15213 USA
[2] Univ Calif San Francisco, Dept Neurol Surg, San Francisco, CA 94143 USA
[3] Univ Toronto, Sunnybrook Hlth Sci Ctr, Dept Crit Care Med, Toronto, ON M4N 3M5, Canada
[4] Univ Pittsburgh, Neurotrauma Clin Trials Ctr, Med Ctr, Pittsburgh, PA 15213 USA