1. Department of Surgery, Center for Advanced Neurology and Neurosurgery, Porto Alegre, Rio Grande do Sul, Brazil,
2. Department of Neurosurgery, Hospital Padilla, Country Las Yungas, Yerba Buena, Tucumuán, Argentina,
3. Department of Neurosurgery, Hospital Italiano de Buenos Aires, Peron, Buenos Aires, Argentina,
4. Department of Serviço de Neurocirurgia, Hospital Ministro Costa Cavalcanti Sanatório Le Blanc, Foz do Iguacu, Paraná, Brazil,
5. Department of Neurosurgery, Pontificical Catholic University of Rio Grande do Sul, Porto Alegre,
6. Department of Neurosurgery, Center for Advanced Neurology and Neurosurgery, São Leopoldo, Rio Grande do Sul, Brazil.