[1] Univ Alabama Birmingham, Div Prevent Med, 1720 2nd Ave South,Med Towers 636, Birmingham, AL 35294 USA
[2] Univ Alabama Birmingham, Dept Surg, Birmingham, AL 35294 USA
[3] Univ Alabama Birmingham, Dept Neurol, UAB Stn, Birmingham, AL 35294 USA
[4] Univ Kentucky, Ctr Hlth Serv Res, Lexington, KY USA
[5] Emory Univ, Dept Neurol, Atlanta, GA 30322 USA