1. Department of Clinical Neuroscience, Karolinska Institute, 171 76 Stockholm, Sweden
2. Department of Surgical Sciences, Uppsala University, 752 36 Uppsala, Sweden
3. Department of Neurosurgery, Karolinska University Hospital, 171 76 Stockholm, Sweden
4. Sweden Capio Spine Center Stockholm, Löwenströmska Hospital, 194 89 Upplands-Väsby, Sweden
5. Department of Medical Sciences, Örebro University, 701 82 Örebro, Sweden