[1] Massachusetts Gen Hosp, Dept Radiol, Div Intervent Neuroradiol Endovasc Neurosurg, Boston, MA 02114 USA
[2] Harvard Univ, Sch Med, Boston, MA 02114 USA
[3] Massachusetts Gen Hosp, Dept Neurosurg, Boston, MA 02114 USA
[4] Massachusetts Gen Hosp, Dept Pathol, Boston, MA 02114 USA
[5] Beth Israel Deaconess Med Ctr, Dept Surg, Div Neurosurg, Boston, MA 02215 USA