Department of Neurosurgery, Maastricht University Medical Center, Maastricht, The Netherlands. CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, The Netherlands. Department of Neurosurgery, Zuyderland Medical Center, Heerlen, The Netherlands. Department of Epidemiology, Maastricht University, Maastricht, The Netherlands. Department of Neurology, Zuyderland Medical Center, Heerlen, The Netherlands.