[1] Gachon Univ, Coll Med, Dept Neurosurg, Spine Ctr,Gil Med Ctr, Incheon, South Korea
[2] Seoul Natl Univ, Dept Neurosurg, Coll Med, 101 Daehak Ro, Seoul 03080, South Korea
[3] Seoul Natl Univ Hosp, Dept Neurosurg, Seoul, South Korea
[4] Seoul Natl Univ, Dept Brain & Cognit Sci, Coll Nat Sci, Seoul, South Korea
[5] Seoul Natl Univ Hosp, Div Med Stat, Med Res Collaborating Ctr, Seoul, South Korea
[6] Korean Armed Forces Capital Hosp, Dept Neurosurg, Seongnam, South Korea
[7] Seoul Natl Univ, Dept Neurosurg, Boramae Hosp, Seoul, South Korea