[1] Mayo Clin, Coll Med, Dept Neurosurg, Jacksonville, FL 32224 USA
[2] Mayo Clin, Coll Med, Mayo Grad Sch, Rochester, MN USA
[3] Univ Texas MD Anderson Canc Ctr, Dept Radiat Oncol, Houston, TX 77030 USA
[4] Stanford Univ, Sch Med, Inst Stem Cell Biol & Regenerat Med, Stanford, CA 94305 USA
[5] Mayo Clin, Coll Med, Dept Neurosci, Jacksonville, FL 32224 USA
[6] Mayo Clin, Coll Med, Dept Canc Biol, Jacksonville, FL 32224 USA