[1] Seoul Natl Univ, Coll Med, Dept Med, 103 Daehak Ro, Seoul 03080, South Korea
[2] Newcastle Univ, Fac Med Sci, Sch Med, Newcastle Upon Tyne NE2 4HH, England
[3] Seoul Natl Univ Hosp, Dept Neurosurg, 101 Daehak Ro, Seoul 03080, South Korea
[4] Seoul Natl Univ, Coll Med, Dept Neurosurg, 103 Daehak Ro, Seoul 03080, South Korea
[5] Seoul Natl Univ, Med Res Ctr, Neurosci Res Inst, 101 Daehak Ro, Seoul 03080, South Korea
[6] Seoul Natl Univ Hosp, Med Res Collaborating Ctr, Div Med Stat, 103 Daehak Ro, Seoul 03080, South Korea
[7] Emory Univ, Sch Med, Dept Orthopaed Surg, Atlanta, GA 30322 USA
[8] Bokwang Hosp, Dept Neurosurg, 128 Guma Ro, Daegu 24853, South Korea
[9] Seoul Natl Univ, Coll Med, Dept Med Device Dev, 103 Daehak ro, Seoul 03080, South Korea
[10] Sinchon Yonsei Hosp, Dept Neurosurg, 110 Seogang ro, Seoul, South Korea