Todd J. Schwedt is Assistant Professor, Departments of Neurology and Anesthesiology, and Director, Washington University Headache Center, Washington University School of Medicine, St. Louis, USA. Jonathan P. Gladstone is Director of the Gladstone Headache Clinic, Director of Neurology and Headache Medicine at Cleveland Clinic Canada, Co-Director of the Child and Adolescent Headache Clinic at The Hospital for Sick Children, Headache Specialist at the Toronto Rehabilitation Institute's WSIB Head and Neck Injury Clinic and Sunnybrook Health Sciences Centre in Toronto, Ontario, Canada. He is a Director of the Canadian Headache Society. Ronald Allan Purdy is Professor and Head, Department of Medicine, Dalhousie University, and District Chief, Department of Medicine, Capital Health, Halifax, Canada. David W. Dodick is Professor of Neurology at Mayo Clinic, Arizona, USA. He is also President-Elect of the American Headache Society and Editor of Cephalalgia.