The role of neuropsychology in prodromal dementia

Abstract

SUMMARY Before dementia becomes manifest, it is preceded by a long period during which neuropathology exists without clinical symptoms, termed the prodromal stage of dementia (ProD). Owing to its relevance for clinical and research aspects, many efforts are being made to define, diagnose and investigate ProD in greater detail. The ProD state has often been studied in Alzheimer’s disease (AD), whereas less is known about the prodromes of the vascular, extrapyramidal and frontotemporal dementias. Since the operational criteria of ProD are unclear, many studies act on the assumption that ProD and mild cognitive impairment are equivalent concepts. However, owing to several methodological problems with the mild cognitive impairment construct, the viewpoint taken here is that ProD can be understood more profoundly in cohorts of normal elderly subjects. This article discusses the neuropsychological findings of longitudinal, population-based studies, which included elderly, normal subjects, who were followed for years, and made case–control comparisons. Neuropsychological findings clearly revealed deficits in cases (subjects who developed dementia later, mostly AD), which were present already at baseline. Cognitive abnormalities were apparent in the domains of episodic memory, but also in tasks tapping executive, psychomotor and visuospatial functions, attention and naming. Although subtle, these impairments were significant at the group level and often demonstrated deterioration to dementia. Early cognitive deficits of the ProD stage therefore represent markers for the identification of incident AD. It is concluded that neuropsychology is a useful method to screen subjects for ProD at an early time point, when individuals are still normally functioning.