Ricardo Díaz-Romero1, Pilar Avendaño2, Gustavo Coloma2. 1. Department of Neurosurgery, Hospital Insular of Las Palmas, Plaza Doctor Pasteur, s/n., 35016, Las Palmas de Gran Canaria, Spain. ricdrp@yahoo.com. 2. Department of Neurosurgery, Hospital Insular of Las Palmas, Plaza Doctor Pasteur, s/n., 35016, Las Palmas de Gran Canaria, Spain.