Kshitij Mankad MRCP FRCR Consultant Paediatric Neuroradiologist, Great Ormond Street Hospital, London, UK Edward T D Hoey MB BCh MRCP FRCR Consultant Radiologist, Heartlands Hospital, Birmingham, UK Sahil Chhabda BSc (Hons) BMBS Specialist Registrar in Clinical Radiology, Chelsea and Westminster Hospital, London, UK