1. From the Institute of Clinical Radiology, Westfaelische Wilhelms-University of Münster (P.B.S., A.K., M.W., W.H.), University Hospital of Muenster, Germany
2. Institute of Neuroradiology, University Hospital of Luebeck, Germany (A.K.)
3. Department of Neurosurgery (M.S.), University Hospital of Muenster, Germany
4. Department of Neurology (J.M.), University Hospital of Muenster, Germany
5. Department of Diagnostic and Interventional Neuroradiology, University Medical Center Hamburg-Eppendorf, Germany (J.N., G.B., J.F., U.H.).