1. Service of Diagnostic and intervention Radiology, Hospital of Sion, Centre Hospitalier du Valais Romand, Switzerland
2. Neurology Service, Hospital of Sion, Centre Hospitalier du Valais Romand, Switzerland
3. Division of Interventional Neuroradiology, The Johns Hopkins Hospital, Baltimore, MD, USA
4. Unit of Neuroradiology, Service of Diagnostic and Intervention Radiology, Hospital of Sion, Centre Hospitalier du Valais Romand, Switzerland