Imaging and neuropsychological correlates of white matter lesions in different subtypes of Mild Cognitive Impairment: A systematic review

BACKGROUND: White matter lesions (WML) are prevalent in older adults. The association between WML and cognition in different subtypes of Mild Cognitive Impairment (MCI) is inconsistent in the literature. OBJECTVES: We aim to provide a systematic review on the impact of WML in different subtypes of MCI, and discuss the recent findings on white matter plasticity. METHODS: We reviewed peer-reviewed articles from January 2011 to August 2016 and identified 12 studies investigating the association between WML and subtypes of MCI with both neuroimaging and cognitive measures. RESULTS: Our review shows that 1) WM abnormality was identified between different subtypes of MCI and healthy controls on diffusion imaging; 2) neither visual ratings of WML nor its volumetry differentiate different subtypes of MCI or its prognosis to dementia; and 3) cognitive correlates of WML were evident in the Amnestic-type MCI in the domains of memory, language, psychomotor speed, attention and executive functions. CONCLUSION: Cognitive reserve and the plasticity of white matter may modulate the impact of WML on the manifestation of the neurodegenerative disease. Further research is needed to study the plasticity of white matter in the MCI population to evaluate its potential clinical application.