Professor Charles ffrench-Constant, Professor of Multiple Sclerosis Research, presents the Medical Detectives lecture, "Why Doesn't the Brain Repair Itself?". The patient disabled by spinal cord injury or multiple sclerosis illustrates the consequences of the failure of repair in the brain after injury. But why does this fail? Other tissues such as skin repair very well, so what factors make the brain different? This talk examines the clues that experiments have given us as to the identity of the culprits. How is current research trying to deal with them, and why might it be that they turned to crime in the first place? Recorded on 7 November 2013 at the University of Edinburgh's Anatomy Lecture Theatre.