1. Department of Surgery, The Center for Advanced Neurology and Neurosurgery, Porto Alegre, Rio Grande do Sul, Brazil,
2. Department of Neurosurgery, Hospital Padila, Country Las Yungas, Yerba Buena, Tucumán,
3. Department of Neurosurgery, Hospital Italiano de Buenos Aires, Perón, Buenos Aires, Argentina,
4. Serviço de Neurocirurgia, Hospital Ministro Costa Cavalcanti Sanatório Le Blanc, Rua Joao Rouver, Foz do Iguaçu, Parana,
5. Department of Neurosurgery, Pontifical Catholic University of Rio Grande do Sul, Luciana de Abreu, Porto Alegre,
6. Department of Neurosurgery, Center for Advanced Neurology and Neurosurgery, São Leopoldo, Rio Grande do Sul, Brazil.