1. Skull Base and Cerebrovascular Laboratory, Department of Neurosurgery, University of California San Francisco, San Francisco, CA 94143, USA
2. Department of Neurosurgery, Hospital Universitario de Canarias, 38320 Tenerife, Spain
3. Department of Neurosurgery, University of California San Francisco, San Francisco, CA 94143, USA
4. Center for Cerebrovascular Research, University of California San Francisco, San Francisco, CA 94143, USA