The text, comprising 14 chapters across five sections, covers clinical presentations, mechanisms, associated conditions, and clinical management. The Clinical Presentations and Mechanisms section reviews the underpinnings and clinical expressions of PTSD and mild TBI, both individually and in combination. A chapter on mild TBI reviews definitions, the mechanics of injury, cellular and chemical neuropathology, and neuroimaging. A chapter on poor outcome in mild TBI provides an analysis of the complex factors that have an impact on brain injury, examining the issue from a combined biological, psychological, and social perspective. The later chapters in this section review clinical and neurobiological aspects of PTSD, how they integrate and change in the presence of mild TBI, and their impact on cognition in combined PTSD and mild TBI.