1. Department of Neurosurgery, Leiden University Medical Center, Leiden, the Netherlands
2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
3. Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
4. Department of Neurosurgery, Haaglanden Medical Centre, The Hague, the Netherlands
5. University Neurosurgical Center Holland, Leiden University Medical Center, Haaglanden Medical Center and Haga Teaching Hospital, Neurosurgery, Leiden, the Netherlands