1. From the Departments of Interventional Neuroradiology (R.H.S., G.S., A.K., R.M., T.K., K.T., R.W.) and Neurosurgery (R.H.S., M.T., I.R.), University Health Network, Toronto Western Hospital, Toronto, Ontario, Canada; and Department of Neurology and Neurosurgery, University Medical Centre Utrecht, Utrecht, The Netherlands (G.J.E.R.).