Cognition and cognitive impairment in Parkinson’s disease

Although the neuropathology underlying cognitive impairments in PD broadly conforms to what is termed a ‘subcortical’ syndrome, there is considerable inter-patient heterogeneity.⁶ This variation has led to the suggestion that patients with PD and cognitive impairments can be categorised into those with either frontostriatal, or posterior cortical, disruption.^6-9 Interestingly, it has been suggested that the pathology underlying a patient’s cognitive impairment can predict the subsequent development of dementia.⁹ The five-year ‘CamPaIGN’ cohort study observed that patients with ‘frontal–executive’ impairments (linked to COMT genotype and dopaminergic medication) are significantly less likely to develop dementia, whereas patients with ‘posterior–cortical’ impairments (linked to MAPT genotype and ageing) are more likely to develop dementia.⁹ It is questionable, however, to what extent this distinction can be used to discriminate whether individual patients are likely to progress to developing dementia or not.⁷

References:
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7. Biundo R, Weis L, Antonini A. Cognitive decline in Parkinson’s disease: the complex picture. NPJ Parkinson’s Disease 2016; 2: 16018.

8. Goldman JG, Litvan I. Mild cognitive impairment in Parkinson’s disease. Minerva Med 2011; 102 (6): 441–459.

9. Williams-Gray CH, Evans JR, Goris A, et al. The distinct cognitive syndromes of Parkinson’s disease: 5 year follow-up of the CamPaIGN cohort. Brain 2009; 132 (Pt 11): 2958–2969.