Associations between cognitive function and striatal DAT loss in Parkinson’s disease with mild cognitive impairment

Objectives: Cognitive impairment in Parkinson's disease (PD) is common non-motor feature. However, the underlying pathophysiology of cognitive decline is not known. We investigated the association of striatal dopamine transporter (DAT) loss with cognitive function and cerebral cortical metabolism in patients with PD.

Methods: Twenty-eight patients (63.1±7.1 yrs, M:F=15:13) with moderately advanced stage of PD were included the analysis, of whom 15 (53.6 %) were diagnosed with mild cognitive impairment (MCI). All patients underwent ¹⁸F-FP-CIT PET/CT, Seoul Neuropsychological Screening Battery (SNSB) and ¹⁸F-FDG PET/CT within 2 weeks of interval. We calculated specific to non-specific binding ratio (SNBR) on ¹⁸F-FP-CIT PET images using 12 striatal subregional VOIs and 1 occipital VOI template as a reference region. Age-adjusted striatal subregional SNBR (%BR) was compared in two groups; PD versus PD-MCI.

Results: There were no statistical difference of age, age of onset, disease duration, UPDRS part III score and level of education between two groups (p>0.05). PD-MCI demonstrated low %BR of left anterior caudate (p=0.020), left ventral striatum (p=0.005), right anterior caudate (p=0.002), right anterior putamen (p=0.006), right posterior caudate (p=0.007), right ventral putamen (p=0.018) and right ventral striatum (p=0.001) when compared with PD without cognitive impairment. Striatal DAT binding revealed correlation with inhibitory control (r=0.552, p=0.003) and visuospatial function (r=0.610, p=0.001), but not with memory function.

Conclusions: The DAT binding of the striatum were significantly correlated with the cognitive impairment in particular inhibitory control and visuospatial function in moderately advanced stage of PD-MCI patients.