1. Students’ Scientific Circle of Neurosurgery , Neurosurgery Department, , Gdansk 80-952 , Poland
2. Medical University of Gdansk , Neurosurgery Department, , Gdansk 80-952 , Poland
3. Neurosurgery Department, Medical University of Gdansk , Gdansk 80-952 , Poland
4. Cardiac Surgery Department, Medical University of Gdansk , Gdansk 80-952 , Poland
5. Department of Neurosurgery, Provincial Specialist Hospital in Słupsk , Hubalczyków 1, Słupsk 76-200 , Poland