1. Department of Neurosurgery, Santa Paula Hospital, Rua Barata Ribeiro 239/12, Bela Vista, 01332-001 São Paulo, SP, Brazil
2. Department of Neurosurgery, Cajuru University Hospital, Pontifícia Universidade Católica do Paraná, Rua Sao Jose 300, Cristo Rei, 80050-350 Curitiba, PR, Brazil
3. Department of Surgery, Division of Post Graduation, Federal University of Rio Grande do Sul, Avenida Paulo Gama 110, Farroupilhas, 90040-060 Porto Alegre, RS, Brazil