[1] Mayo Clin, Dept Neurol, Phoenix, AZ 85054 USA
[2] Univ Arizona, Fac Med, Tucson, AZ USA
[3] Mayo Clin, Dept Biostat, Scottsdale, AZ USA
[4] Mayo Clin, Dept Res, Scottsdale, AZ USA
[5] Maricopa Integrated Hlth Syst, Dept Emergency Med, Phoenix, AZ USA