[1] Hanyang Univ, Med Ctr, Dept Anesthesiol & Pain Med, Seoul 133792, South Korea
[2] Hanyang Univ, Med Ctr, Dept Neurosurg, Seoul 133792, South Korea
[3] Hanyang Univ, Dept Anat & Cell Biol, Seoul 133792, South Korea
[4] Natl Med Ctr, Dept Neurosurg, Seoul, South Korea
[5] Redcross Coll, Dept Nursing, Seoul, South Korea
[6] Wonjin Green Hosp, Dept Occupat & Environm Med, Seoul, South Korea