1. Department of Radiology; University Hospital KU Leuven; Herestraat 49 Leuven B-3000 Belgium
2. Department of Radiology; Maastricht University Medical Centre; P.O. Box 5800 Maastricht 6202 AZ The Netherlands
3. Department of Neurosurgery; University Hospital KU Leuven; Herestraat 49 Leuven B-3000 Belgium
4. Department of Neurology; University Hospital KU Leuven; Herestraat 49 Leuven B-3000 Belgium