This introductory chapter presents an overview of key concepts discussed in this book, which provides a clinically relevant review of non-Alzheimer's and atypical dementia syndromes. The book also provides comprehensive overview of the differential diagnoses for atypical dementia that could be utilized by health-care providers who encounter these patients in their clinical practice, including neurologists, primary care providers, psychiatrists, neuropsychologists, nurses, social workers, etc. The book includes clinical case studies to help illustrate key or unique diagnostic features of each disorder and to provide a real-world view of how each disorder might present in the clinic. The effect of vascular cognitive impairment (VBI) is additive and might be worsened by the presence of other underlying neuropathological conditions. Past medical and family history is important to review for a history of cancer, familial autoimmune disorders or cancers, smoking history, and constitutional symptoms.