Classification of atypical parkinsonism per pathology versus phenotype.

The umbrella term "atypical parkinsonism" refers to a clinical presentation with various causes, emphasizing the clinical commonality of diseases in which atypical parkinsonism can present. This term is useful for describing the phenomenology of a movement disorder and to classify patients according to their clinical presentation. In contrast to this classification per phenotype, a classification per pathology is needed when it comes to understanding the pathogenesis and designing and delivering disease-modifying therapeutic interventions. Clinico-pathological correlation studies have revealed enormous clinical heterogeneity and vast clinical overlap in pathologically defined diseases related to atypical parkinsonism. Thus, the classification of patients with atypical parkinsonism per phenotype has limited validity for predicting the underlying pathology. This chapter will contrast the phenotype-driven classification and the pathology-driven classification of neurodegenerative diseases related to atypical parkinsonism and discuss future directions to improve pathology-specific diagnosis.

Clinical and neuropathological differences between Parkinson's disease, Parkinson's disease dementia and dementia with Lewy bodies - current issues and future directions.

Lewy body diseases share clinical, pathological, genetic and biochemical signatures, and are regarded as a highly heterogeneous group of neurodegenerative disorders. Inclusive of Parkinson's disease (PD), Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB), controversy still exists as to whether they should be considered as separate disease entities or as part of the same disease continuum. Here we discuss emerging knowledge relating to both clinical, and neuropathological differences and consider current biomarker strategies as we try to improve our diagnostic capabilities and design of disease modifying therapeutics for this group of debilitating neurodegenerative disorders. This article is part of the Special Issue "Synuclein".