Brain structural MRI correlates of cognitive dysfunctions in Parkinson's disease

Cognitive dysfunction occurs at early stages of Parkinson's disease (PD). Initial studies reported that cognitive dysfunction in early PD only affected fronto-striatal circuits, provoking a marked executive dysfunction. Memory impairment in PD was thought to depend on a problem in retrieving stored information, therefore also reflecting a fronto-striatal dysfunction. However, there is increasing structural MRI evidence of medial temporal lobe atrophy in PD, which may be responsible for memory dysfunction. Other neuropsychological functions usually impaired in PD are semantic fluency, visuoperceptual and visuospatial functions, decision-making and recognition of facial emotions; and impairments in these functions are associated with cortical structural changes assessed by MRI. Overall, although the literature on the topic is scarce, there is increasing evidence of brain structural changes, detectable by MRI, which can explain the neuropsychological deficits early in the clinical disease course before dementia develops. In this review, we summarize the papers that have used structural MRI to study the neuroanatomical correlates of cognitive dysfunctions in PD.