1. Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom
2. Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan
3. College of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan
4. Medical Faculty of the University Duisburg-Essen, Essen, Germany
5. Danish Headache Center, Department of Neurology, Rigshospitalet-Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark