[1] Univ Calif San Francisco, Radiol & Neurosurg, San Francisco, CA 94143 USA
[2] Univ Texas Med Branch, Neurosurg, Galveston, TX USA
[3] Univ Texas MD Anderson Canc Ctr, Radiol & Neurosurg, Houston, TX USA
[4] Northwestern Univ, Feinberg Sch Med, Radiol, Neurosurg,Neurol, Chicago, IL USA