1. Department of Neurosurgery, National Hospital for Neurology and Neurosurgery , London WC1N 3BG , UK
2. Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London , London W1W 7TY , UK
3. Department of Diabetes & Endocrinology, University College London Hospitals NHS Foundation Trust , London NW1 2BU , UK
4. Centre for Obesity and Metabolism, Department of Experimental and Translational Medicine, Division of Medicine, University College London , London WC1E 6BT , UK
5. Digital Surgery Ltd, Medtronic , London WD18 8WW , UK