1. Department of Neurosurgery, University of Illinois College of Medicine at Peoria, Peoria, IL 6156-1649, USA
2. League of Neurosurgery, The Neurologival Institute of Curitiba, 81210-310 Curitiba, PR, Brazil
3. Instituto de Neurologia de Curitiba, 81210-310 Curitiba, PR, Brazil
4. Department of Neurosurgery, University of Illinois College of Medicine at Peoria, Peoria, IL, USA