Florian Bernard1, Philippe Bijlenga2. 1. Division of Neurosurgery, Angers University Hospitals, Angers, France; Laboratory of Anatomy-Faculty of Medicine, Angers, France; CRCINA, UMR 1232 INSERM/CNRS, and EA7315 Team, Angers, France. 2. Division of Neurosurgery, Department of Clinical Neurosciences, Geneva University Hospitals, Switzerland.