1. Department of Neurosurgery, Hospital Central ‘Dr. Ignacio Morones Prieto’, San Luis Potosi, Mexico
2. Department of Neurosurgery, University Clinic Evangelisches Krankenhaus, Oldenburg, Germany
3. Department of Clinical Epidemiology, Universidad Autonoma de San Luis Potosi, Bad Pyrmont, Mexico
4. Department of Neurosurgery, Bathildis Krankenhaus, Bad Pyrmont, Germany