[1] Hirosaki Univ, Dept Neurosurg, Hirosaki, Aomori, Japan
[2] Hirosaki Univ, Dept Emergency Disaster & Gen Med, Hirosaki, Aomori, Japan
[3] Hirosaki Gen Med Ctr, Dept Neurosurg, Hirosaki, Aomori, Japan
[4] Gen Southern Tohoku Hosp, Dept Neurosurg, Iwanuma, Miyagi, Japan
[5] Towada City Cent Hosp, Dept Neurosurg, Towada, Aomori, Japan