1. Department of Anesthesiology and Pain Medicine, Ajou University School of Medicine, Suwon, Korea.
2. Department of Pharmaceutical Service, Ajou University Hospital, Suwon, Korea.
3. Department of Neurology, Ajou University School of Medicine, Suwon, Korea.
4. Department of Neurosurgery, Ajou University School of Medicine, Suwon, Korea.