[1] Beth Israel Deaconess Med Ctr, Dept Emergency Med Adm Off, Boston, MA 02215 USA
[2] Johns Hopkins Univ, Sch Med, Dept Neurol, Baltimore, MD 21231 USA
[3] Johns Hopkins Univ, Sch Med, Dept Otolaryngol, Baltimore, MD 21231 USA
[4] Johns Hopkins Univ, Sch Med, Dept Epidemiol, Baltimore, MD 21231 USA
[5] Johns Hopkins Univ Hosp, Bloomberg Sch Publ Hlth, Baltimore, MD 21231 USA