[1] Stanford Univ, Sch Med, Dept Neurosurg, Stanford, CA 94305 USA
[2] Stanford Univ, Sch Med, Dept Pathol, Stanford, CA 94305 USA
[3] Stanford Univ, Sch Med, Inst Med, Stanford, CA 94305 USA
[4] Stanford Univ, Sch Med, Howard Hughes Med Inst, Stanford, CA 94305 USA