Neuropsychological tests for detection of prodromal DLB: a systematic review

Dementia with Lewy bodies (DLB) is a neurodegenerative dementia, second only to Alzheimer’s Disease Dementia (ADD) in frequency. Research to date has primarily focused on the dementia stage and its symptoms, the prodromal phase remains understudied and poorly defined. This systematic review aimed at reviewing the studies on the earliest cognitive deficits detectable in DLB to define the prodromal cognitive and neuropsychological profile of this condition, with a focus on identifying the most useful neuropsychological tests in clinical practice. Initially 2111 articles were identified via a keyword search in PubMed and Web Of Science. The search was refined through the application of inclusion and exclusion criteria. Of the 78 remaining after application of these criteria, 32 articles reported data acquired with a consistent battery of neuropsychological tests and had tested specifically a prodromal DLB population or a population of DLB patients including those in prodromal or Mild Cognitive Impairment (MCI) stages. These articles were included in the final analysis. Mild impairments in attention and executive functions, along with deficits in visual perception and working memory, were noted in prodromal DLB. When compared with healthy controls, prodromal DLB showed mild impairments in memory and language tasks, while when compared with MCI-AD, prodromal DLB performed better in memory tasks while showing worse performance in visual perceptual, attention, and executive tests. The most sensitive tests for detecting prodromal DLB included the Frontal Assessment Battery, the Digit Symbol Substitution Test, the Stroop test, the AX continuous performance test, the digit span backward, the Rey complex figure copy, the pareidolia test and the Visual Object and Space Perception battery. These impairments seem to reflect the pattern of accumulation of Lewy Bodies (LB) from the brainstem to the cortex, with symptoms beginning as attentional fluctuations due to the impact on the reticular substance, followed by executive dysfunctions, deficits in the attention and working memory as LB damage dopaminergic frontal pathways, and visual perception impairments upon reaching the occipital cortex. This systematic review suggests that a neuropsychological test battery suitable to identify the prodromal stage of DLB should comprehensively evaluate attention, executive functions, working memory, visual spatial and perceptual skills, and praxic-constructive abilities. Further studies validating measures sensitive to detect these early impairments could lead to the standardisation of a specific test battery to be used for the timely detection of the prodromal phase of dementia with Lewy bodies.