The human brain is a vastly complex biological system. Many of its workings are not yet fully understood. It is central to reasoning, thinking, feeling and doing and has fascinated and awed ancient philosophers and modern scientists for centuries. Brain-injury rehabilitation should ideally be sustainable over the long term in order to maximise its benefits to communities. Traumatic brain injury refers to an injury to the brain resulting from mechanical force. Traumatic brain injury provides a good model for exploring some of the striking global differences in brain-related injuries in more detail. In theory at least, brain-related diseases, and to a lesser extent traumatic injuries, should have reasonably consistent incidence and prevalence rates across the world. Even where a specific brain condition has a relatively more predictable incidence and prevalence, variation will still occur for similar reasons to those accounting for injuries.