[1] Stanford Univ, Dept Neurosurg, Palo Alto, CA 94304 USA
[2] Stanford Univ, Sch Med, Palo Alto, CA 94304 USA
[3] Univ Louisville, Dept Neurosurg, Louisville, KY 40292 USA
[4] Univ Louisville, Dept Neurol, Louisville, KY 40292 USA
[5] Univ Louisville, Dept Radiat Oncol, Louisville, KY 40292 USA
[6] VA Palo Alto Hlth Care Syst, Neurosurg Sect, Palo Alto, CA 94304 USA