1 Department of Neurosurgery A, University Hospital of Bordeaux, Bordeaux, France; Laboratory of Anatomy, University of Bordeaux, 33000 Bordeaux, France.
2 Department of Neurosurgery, University Hospital of Clermont-Ferrand, Clermont-Ferrand, France.
3 Department of Neurosurgery A, University Hospital of Bordeaux, Bordeaux, France; Laboratory of Anatomy, University of Bordeaux, 33000 Bordeaux, France. Electronic address: paul.roblot@gmail.com.