1. Department of Clinical Neurosciences, Western General Hospital, Edinburgh;
2. Division of Neurosurgery, Addenbrooke’s Hospital and University of Cambridge, Cambridge;
3. Department of Neurosurgery, National Hospital for Neurology and Neurosurgery, London;
4. Department of Neurosurgery, Charing Cross Hospital, London;
5. Neurosurgical Trials Group, Newcastle University, Newcastle upon Tyne;
6. Department of Neurosurgery, Royal London Hospital, London; and
7. Department of Neurosurgery, James Cook Hospital, Middleborough, United Kingdom