1. Department of Surgery, School of Health Sciences, University Hospital of Ioannina and Faculty of Medicine University of Ioannina Ioannina Greece
2. First Propaedeutic Department of Surgery, National and Kapodistrian University of Athens Hippocration General Hospital Athens Greece
3. First Department of Surgery, National and Kapodistrian University of Athens Laikon General Hospital Athens Greece
4. Department of Neurosurgery University Hospital of Ioannina Ioannina Greece