1. Department of Neurosurgery, University of California, San Francisco, CA, USA,
2. Department of Neurosurgery, University of California, San Francisco, CA, USA
3. Department of Anatomy, University of California, San Francisco, CA, USA
4. Department of Neurosurgery, University of California, San Francisco, CA, USA, Department of Physical Therapy and Rehabilitation Science,University of California, San Francisco, CA, USA