1. Department of Neurosurgery, Cannizzaro Hospital, Catania, Italy
2. Department of Neurosurgery, National Specialist Hospital Garibaldi, Catania, Italy
3. Department of Neurosurgery, Universita degli Studi di Palermo, Palermo, Sicilia, Italy
4. Department of Neurosurgery, Paracelsus Medical Private University, Salzburg, Austria