1. Department of Neurosurgery, Puerta de Hierro Majadahonda University Hospital, Madrid, Spain
2. Statistics Department, Computing Center, C.S.I.C., Madrid, Spain
3. Department of Neurophysiology, Puerta de Hierro Majadahonda University Hospital, Madrid, Spain
4. Molecular Pathology Group, Instituto de Investigación Sanitaria Puerta de Hierro Segovia de Arana (IDIPHISA), Madrid, Spain
5. Department of Pathology, Puerta de Hierro Majadahonda University Hospital, Madrid, Spain