1. Victor Horsley Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, London, United Kingdom
2. UCL Queen Square Institute of Neurology, London, United Kingdom
3. Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, United Kingdom
4. Headache and Facial Pain Group, National Hospital for Neurology and Neurosurgery, London, United Kingdom