1. Department of Neurosurgery; University Hospital of Freiburg; Freiburg Germany
2. Department of Neurosurgery; University Hospital of Essen; Essen Germany
3. Department of Neurology; University Hospital of Freiburg; Freiburg Germany
4. Institute for Medical Biometry and Medical Informatics; University Hospital of Freiburg; Freiburg Germany
5. Department of Neuroradiology; University Hospital of Freiburg; Freiburg Germany