Book excerpt: Intended for general neurologists as well as specialists in multiple sclerosis (MS) and imaging, this book provides comprehensive discussion of central nervous system (CNS) atrophy involving the brain and spinal cord, and both the chapter authors and topics have been selected to provide state-of-the-art reviews. Key issues covered in the book include pathogenesis and its mechanisms, technical aspects of MRI measurement, the relationship between CNS atrophy and other MRI metrics, clinical relevance, the association with neurobehavioral and genetic-immunologic components of MS, and the effects of disease-modifying therapies on tissue atrophy. Pros and cons of different technical approaches are discussed critically. Special attention is devoted to CNS atrophy as a clinically relevant biologic marker of the MS disease process.