N Lützen1, W D Niesen2, J Kalbhenn3, H Urbach4. 1. Department of Neuroradiology, University Medical Center Freiburg, Breisacher Straße 64, 79106, Freiburg, Germany. niklas.luetzen@uniklinik-freiburg.de. 2. Department of Neurology, University Medical Center Freiburg, Breisacher Straße 64, 79106, Freiburg, Germany. 3. Department of Anaesthesiology and Critical Care Medicine Freiburg, Hugstetter Straße 55, 79106, Freiburg, Germany. 4. Department of Neuroradiology, University Medical Center Freiburg, Breisacher Straße 64, 79106, Freiburg, Germany.