[1] Boston Univ, Dept Neurol, Boston, MA 02215 USA
[2] Univ Penn, Dept Neurol, Philadelphia, PA 19104 USA
[3] Univ Penn, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[4] Univ Penn, Leonard Davis Inst Hlth Econ, Philadelphia, PA 19104 USA
[5] Thomas Jefferson Univ, Dept Emergency Med, Philadelphia, PA 19107 USA
[6] Univ Alabama Birmingham, Hlth Serv & Outcomes Res Ctr Outcome & Effectiven, Birmingham, AL USA
[7] Univ Alabama Birmingham, Ctr Excellence Comparat Effectiveness Res Elimina, Minor Hlth & Hlth Dispar Res Ctr, Birmingham, AL USA
[8] Univ Alabama Birmingham, Dept Epidemiol, Birmingham, AL USA
[9] Univ Cincinnati, Dept Neurol, Cincinnati, OH 45221 USA