The neuropsychological profile of vascular cognitive impairment not demented: a meta-analysis

The most common cause of vascular cognitive impairment not demented (VCIND) is cerebral small vessel disease leading to diffuse subcortical white matter lesions. While many studies indicate that the core cognitive features of VCIND are executive dysfunction and impaired processing speed, this finding is not always consistent, and may be partially dependent on the comparison group applied. Hence, we undertook two systematic meta-analytic reviews on neuropsychological test performance across eight cognitive domains: between VCIND and healthy controls (data from 27 studies), and between VCIND and non-vascular mild cognitive impairment (nv-MCI; data from 20 studies). Our quantitative synthesis of the research literature demonstrates that individuals with VCIND show weaknesses across all cognitive domains relative to healthy controls, with the greatest impairment in the domain of processing speed (Md = -1.36), and the least affected being working memory (Md = -.48) and visuospatial construction (Md = -.63). When compared directly with nv-MCI, individuals with VCIND had significantly greater deficits in processing speed (Md = -.55) and executive functioning (Md = -.40), while those with nv-MCI exhibited a greater relative deficit in delayed memory (Md = .41). Our analyses indicate that disruption to subcortical white matter tracts impairs more cognitive processes than is typically thought to be directly related to the fronto-subcortical network. The data also suggest that differing brain aetiologies can be responsible for similar cognitive profiles. Although the findings do not evince diagnostic value, they allude to the interconnectivity of disparate cognitive processes and call for further research on the behavioural outcome of network disruption.