Neurological, Cognitive, and Clinical Biomarkers of Lewy Body Dementia Subtypes: A Literature Review

Abstract

Introduction: Diagnosing the etiology underlying dementia symptoms can be difficult because of the broad nature of shared cognitive impairments across dementia subtypes. Therefore, we sought to differentiate the cognitive profiles of Alzheimer’s disease (AD) from vascular dementia (VaD) and Lewy body dementia (LBD). Methods: PubMed, ScienceDirect, Web of Science, Google Scholar, and PsychINFO were searched for studies comparing the cognitive profile of AD to those of VaD and LBD along the domains of memory, language, and executive function. Results: Short-term and episodic memory were more severely impaired in AD than VaD and LBD. Semantic memory was more impaired in AD than LBD, but it was similarly impaired in AD and VaD. Semantic fluency was worse in AD than in VaD, and phonemic fluency was worse in AD compared to VaD and LBD. Naming was more impaired in AD compared to VaD and LBD. Executive function impairments were similar or less severe in AD relative to VaD and LBD. Discussion: Findings may be explained through neuropathological correlates of each disease. Tau proteins targeting the medial temporal lobes and synaptic loss in prefrontal cortices in AD may explain greater memory deficits in AD relative to VaD and LBD. In those with AD, the temporal lobes undergo greater atrophy than in those with VaD and LBD, possibly contributing to the greater semantic fluency impairments in AD. Greater white matter loss in frontal lobes in VaD may be a reason for a worse phonemic fluency in VaD relative to AD. Executive function impairments may be attributable to more deep white matter hyperintensities in those with VaD and more dopaminergic dysfunction of the basal ganglia in those with LBD relative to those with AD. Conclusion: Understanding the cognitive profiles that differentiate AD from VaD and LBD would aid in more efficient and accurate diagnoses of dementia etiologies. Diagnoses could be further improved by using cognitive assessment in addition to neural and physiological measures. This knowledge may help identify individuals at risk of developing dementia, helping clinicians intervene early and prevent progression to severe stages.