1. From the Department of Diagnostic and Interventional Neuroradiology (G.B., F.R., U.H., T.D.F., H.L., S.G., J.F., F.F.), University Medical Center Hamburg-Eppendorf, Germany
2. Institute of Medical Biometry and Epidemiology (G.S.), University Medical Center Hamburg-Eppendorf, Germany
3. Department of Clinical Radiology, University Hospital Münster, Germany (P.S., A.K.).
4. Department of Neurology (M.D.-C., G.T.), University Medical Center Hamburg-Eppendorf, Germany