[1] Yale Sch Med, Neurosurg, New Haven, CT USA
[2] Weill Cornell Med Coll, Astoria, NY USA
[3] McMaster Univ, Hamilton, ON, Canada
[4] Univ Edinburgh, Edinburgh, Midlothian, Scotland
[5] Massachusetts Gen Hosp, Boston, MA 02114 USA
[6] Johns Hopkins Univ, Baltimore, MD USA
[7] Univ Cincinnati, Cincinnati, OH USA