1. Keck School of Medicine of the University of Southern California; Department of Otolaryngology - Head and Neck Surgery; Los Angeles CA USA
2. Pain Research Unit, Churchill Hospital; Cochrane Pain, Palliative and Supportive Care Group; Churchill Hospital Oxford Oxfordshire UK OX3 7LE
3. Central Manchester University Hospitals NHS Foundation Trust; Department of Otolaryngology, Head and Neck Surgery; Oxford road Manchester UK M13 9WL
4. Cochrane UK; Summertown Pavilion 18 - 24 Middle Way Oxford UK OX2 7LG