1. Headache and Facial Pain Group, University College London Queen Square Institute of Neurology, London, UK
2. Headache and Facial Pain Group, The National Hospital for Neurology and Neurosurgery, London, UK
3. Department of Neuromedicine and Movement Science, NTNU Norwegian University of Science and Technology, Trondheim, Norway
4. Department of Maxillofacial Surgery, St Olav's University Hospital, Trondheim, Norway
5. Department of Neurosurgery, St Olav's University Hospital, Trondheim, Norway
6. NorHEAD, Norwegian Headache Research Centre, Norway
7. National Advisory Unit on Headaches, Department of Neurology and Clinical Neurophysiology, St Olav's Hospital, Trondheim, Norway