1. Department of Neurological Surgery, University of California, San Francisco, CA 94143, USA
2. San Francisco Veterans Affairs Medical Center, San Francisco, CA 94121, USA
3. Department of Neurology, University of California, San Francisco, CA 94143, USA
4. Department of Neurosurgery, Hokkaido University, Sapporo 060-0808, Japan
5. Department of Anatomy, Yonsei University, Seoul 03722, Republic of Korea