1. Department of Neurosurgery, University Hospital Basel, University of Basel, Basel, Switzerland
2. Department of Neurosurgery, Neurocenter of Southern Switzerland, Regional Hospital of Lugano, Lugano, Switzerland
3. Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Basel, Switzerland
4. Department of Neurosurgery, University Malaya Specialist Centre, University of Malaya, Kuala Lumpur, Malaysia