Amyloid PET Imaging in Lewy Body Disorders

Lewy body (LB) disorders, including Parkinson disease (PD), Parkinson disease dementia (PDD), and dementia with Lewy bodies (DLB), are the second most common type of neurodegenerative dementia. Although the pathological hallmarks of LB disorders are Lewy bodies and Lewy neurites, cortical amyloid-beta (A beta) deposition is also often seen. The relationship between A beta pathology and dementia in LB disorders is unclear. Recently, positron emission tomography A beta ligands have been developed that enA beta le in vivo imaging of A beta. In this paper we review amyloid imaging studies in LB disorders. LB disorders are associated with lower mean cortical A beta ligand binding compared with Alzheimer disease. In DLB and PDD many subjects have normal levels of cortical A beta, though a subset showincreased A beta ligand binding. Those with DLB show greater ligand binding than PDD; binding does not appear to be increased in PD without dementia. Cortical A beta deposition may be a factor in the development of cognitive impairment in some cases of dementia in LB disorders. Amyloid imaging is of limited use in the diagnosis of LB disorders but A beta deposition may predict the future development of dementia in PD. Reports of correlation between A beta deposition and symptom profile, severity, and progression have been inconsistent. Some results suggest a synergistic interaction between A beta and alpha-synuclein. Interpretation of the current evidence is hampered by differing methodologies across studies and small sample sizes. Large, prospective longitudinal studies are needed to clarify the association of A beta with symptom development, progression, severity, and treatment response in LB disorders.