1. 1Department of Neurosurgery, Charles University, 1st Faculty of Medicine, Military University Hospital, Prague;
2. 2Department of Anatomy and Biomechanics, Faculty of Physical Education and Sport, Charles University, Prague, Czech Republic;
3. 3Department of Neurosurgery, Royal Hallamshire Hospital, Sheffield, United Kingdom; and
4. 4Department of Radiology, Military University Hospital, Prague, Czech Republic