[1] Univ Fed Minas Gerais, Dept Neurosurg, Clin Hosp, Belo Horizonte, MG, Brazil
[2] Madre Teresa Hosp, Dept Radiol, Belo Horizonte, MG, Brazil
[3] Madre Teresa Hosp, Dept Neurosurg, Belo Horizonte, MG, Brazil
[4] Univ British Columbia, Div Neurosurg, Vancouver, BC V5Z 1M9, Canada