Neural correlates of cognitive impairment in Parkinson's disease : a review of structural MRI findings

Cognitive impairment is one of the most salient non-motor symptoms of Parkinson ’ s disease (PD). Cognitive decline poses a significant burden on the patient as well as the caregiver and a better understanding of the underlying pathological processes will aid in directing disease-specific treatment. In recent years, significant progress in the understanding of the underlying mechanisms of cognition in PD has been made using neuroimaging modalities. In this review, we will discuss the evidence for gray matter atrophy and cortical thinning, diffusivity changes and white matter hyperintensities in dementia, mild cognitive impairment and in several cognitive domains. Structural MRI studies have revealed considerable changes in gray and white matter in PD patients with cognitive dysfunction, showing marked atrophy and diffusivity changes in patients with dementia. The neural substrates of mild cognitive impairment in PD are more variable, perhaps reflecting a heterogeneous cohort with patients showing deficits in various cognitive domains. This review further highlights the potential areas of future research avenues in cognitive impairment in PD