1 Department of Neurosurgery, Geisinger, Danville, Pennsylvania, USA.
2 Department of Neurosurgery, Geisinger, Danville, Pennsylvania, USA; Research Institute of Neurointervention, Paracelsus Medical University, Salzburg, Austria.
3 Department of Radiology, Geisinger, Danville, Pennsylvania, USA.
4 Department of Neurosurgery, Geisinger, Danville, Pennsylvania, USA. Electronic address: cmschirmer@gmail.com.