1. Department of Surgery, Medicine and Veterinary Anatomy, Faculty of Veterinary Sciences, Campus de Vegazana, University of Léon, 24071 Léon, Spain
2. Department of Neurosurgery, Stanford School of Medicine, Stanford University, Palo Alto, CA 94305, USA
3. Institute of Biomedicine (IBIOMED), Faculty of Veterinary Sciences, Campus de Vegazana, University of León, 24071 León, Spain