1. Department of Neurosurgery, Imamura General Hospital, Kagoshima, Japan.
2. Department of Neurosurgery, National Hospital Organization Kagoshima Medical Center, Kagoshima, Japan.
3. Department of Neurosurgery, Sakaki Neurosurgical Clinic, Kagoshima, Japan.
4. Department of Neurosurgery, Kagoshima University, Kagoshima, Japan.