1. Institute of Neuroscience and Physiology, Department of Clinical Neuroscience, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
2. Institute of Medicine, Neurology, Uppsala University Hospital, Uppsala, Sweden
3. Department of Neurosurgery, Sahlgrenska University Hospital, Gothenburg, Sweden
4. Department of Neurosurgery, St. Olavs University Hospital, Trondheim, Norway