1. Department of Neurosurgery, St George’s University Hospital, London, UK
2. Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, London, UK
3. Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, London, UK
4. Department of Neurosurgery, Imperial College Healthcare NHS Trust, London, UK
5. Department of Neurosurgery, Sheffield Teaching Hospitals, Sheffield, UK