1. Department of Anesthesiology and Pain Medicine, Ajou University School of Medicine, Suwon, Korea.
2. Department of Neurosurgery, Ajou University School of Medicine, Suwon, Korea.
3. Department of Surgery, Ajou University School of Medicine, Suwon, Korea.
4. Department of Emergency Medicine, Ajou University School of Medicine, Suwon, Korea.