1 The Pain Management Programme, Walton Centre NHS Foundation Trust, Lower Lane, Liverpool, L9 7LJ, UK. Selina.johnson@thewaltoncentre.nhs.uk.
2 Pain Research Institute, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, UK. Selina.johnson@thewaltoncentre.nhs.uk.
3 Pain Research Institute, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, UK.
4 Centre for Health Economics and Medicines Evaluation (CHEME) Department, Bangor University, Bangor, Wales, UK.
5 Department of Neurophysiology, Mannheim Centre for Translational Neurosciences, Medical Faculty Mannheim, Ruprecht Karls-University Heidelberg, Heidelberg, Germany.
6 The Pain Management Programme, Walton Centre NHS Foundation Trust, Lower Lane, Liverpool, L9 7LJ, UK.