[1] Johns Hopkins Univ, Sch Med, Dept Anesthesiol & Crit Care Med, Baltimore, MD 21205 USA
[2] Capital Med Univ, Xuanwu Hosp, Dept Neurosurg, Beijing 100053, Peoples R China
[3] Xi An Jiao Tong Univ, Affiliated Hosp, Hong Hui Hosp, Dept Orthoped,Med Sch, Xian 710004, Shaanxi, Peoples R China
[4] Capital Med Univ, Dept Neurobiol, Beijing 100069, Peoples R China
[5] Capital Med Univ, Luhe Hosp, Dept Orthoped, Beijing 100020, Peoples R China
[6] Johns Hopkins Univ, Sch Med, Dept Neurol Surg, Baltimore, MD 21205 USA