1 Department of Neurosurgery, Antwerp University Hospital and University of Antwerp, Edegem 2650, Belgium. Electronic address: andrew.maas@uza.be.
2 Department of Neurosurgery, Leiden University Medical Centre, Leiden, Netherlands; Department of Neurosurgery, Haaglanden Medical Centre, The Hague, Netherlands.
3 Department of Neurosurgery, Medical University Innsbruck, Innsbruck, Austria.