Although Alzheimer's disease is the most common cause of dementia, dementia with Lewy bodies (DLB) is another common cause of dementia. In fact, DLB and Parkinson's disease dementia (PDD) account for 10–15% of all cases of dementia. However, only an estimated 20% of patients have “pure” DLB; approximately 80% of patients will also have pathological features of other dementias, namely Alzheimer's disease pathology (Thomas et al, 2017; Yang and Yu, 2017; Karantzoulis and Galvin, 2011). In this chapter, we will discuss the neurobiology and diagnosis of DLB and PDD (collectively known as Lewy body dementias [LBDs]) and other synucleinopathies as well as the hypothesized relationship between Alzheimer's and Parkinson’s. For strategies to ameliorate some of the secondary behavioral symptoms often associated with synucleinopathies and other dementias, the reader is directed to Chapter 5.

MAO: Monoamine oxidase; VMAT: vesicular monoamine transporter