1. Department of Clinical Neurosciences – Neurosurgery, University of Calgary, Calgary, Alberta, Canada
2. Neurosurgery & Spine Specialists, Eastern Maine Medical Center, Bangor, Maine, USA
3. Department of Orthopedics, Universidade de Caxias do Sul, Caxias do Sul, Rio Grande do Sul, Brazil
4. Department of Neurosurgery, Universidade de Caxias do Sul, Caxias do Sul, Rio Grande do Sul, Brazil