[1] Univ Calif San Francisco, Dept Neurol Surg, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Ctr Cerebrovasc Res, Dept Anesthesia & Perioperat Care, San Francisco, CA USA
[3] Univ Calif San Francisco, Dept Radiol & Biomed Imaging, San Francisco, CA USA
[4] Barrow Neurol Inst, Dept Neurosurg, Phoenix, AZ USA