Update on SPECT and PET in parkinsonism - part 2: biomarker imaging of cognitive impairment in Lewy-body diseases.

Purpose of Review: To give an update on recent biomarker imaging studies using single-photon emission computed tomography (SPECT) and positron emission tomography (PET) on cognitive impairment in Lewy-body diseases (LBD).
Recent Findings: Imaging studies of regional cerebral glucose metabolism with [F]fluorodeoxyglucose(FDG)-PET support the concept that Parkinson's disease (PD) with mild cognitive impairment represents a prodromal stage of PD with dementia (PDD). Furthermore, [F]FDG-PET may be suited for risk stratification for dementia in PD. In line with neuropathological studies, preliminary amyloid-beta (Aβ) PET studies suggest that Aβ acts synergistically with Lewy pathology in LBD, leading to an earlier manifestation of cognitive impairment in dementia with Lewy-bodies compared with PDD and a more rapid cognitive decline in PD patients with concomitant Aβ pathology.
Summary: Molecular neuroimaging with SPECT and PET provides unique in-vivo insights into neuropathological and pathophysiological changes underlying cognitive impairment in LBD. Future prospective studies are needed to confirm the prognostic value of [F]FDG-PET and to define the value of amyloid PET and upcoming techniques, such as tau imaging, for diagnosis and prognosis in LBD.