1. Department of Neurosurgery, Mito Medical Center, University of Tsukuba, Mito 310-0015, Japan
2. Department of Neurosurgery, Sato Clinic of Internal Medicine and Neurosurgery, Moriya 302-0117, Japan
3. Department of Neurology, Sato Clinic of Internal Medicine and Neurosurgery, Moriya 302-0117, Japan
4. Department of Neurosurgery, Mito Brain Heart Center, Mito 310-0004, Japan