ABSTRACT
Background & Objectives: Frontal executive dysfunction, which is hypothesized to reflect dorsolateral prefrontal function, predominates in Parkinson’s disease (PD). Visuospatial dysfunction and episodic memory deficit, which are associated with the posterior cortical area, are critical symptoms of mild cognitive impairment in PD (PD-MCI). The first aim of this study is to investigate whether dominant cognitive deficits are caused by posterior cortical dysfunction in drug naïve, de novo PD-MCI patients. The second aim is to analyze the relationship between parkinsonian motor symptoms and the cognitive domain in these patients. Methods: Newly diagnosed PD patients who had not received treatment were divided into two subgroups as follows: PD-MCI (n=39) and PD patients with normal cognition (PD-NC) (n=39). Various neuropsychological tests were performed in all of the patients. The parkinsonian motor subscores were divided into tremor, rigidity, axial impairment, bulbar dysfunction and bradykinesia by the UPDRS motor scores. Results: Verbal episodic memory (immediate recall; p = 0.0001, delayed recall; p = 0.0001, recognition; p = 0.003), visual episodic memory (immediate recall; p = 0.0001, delayed recall; p = 0.002) and visuospatial function (p = 0.046) were lower in the PD-MCI group than in the PD-NC group. In the analysis of the correlation of the motor components to the cognitive tests, impairment in visual episodic memory correlated with axial symptoms (immediate recall; r = -0.441, p = 0.021, delayed recall; r = -0.393, p = 0.042). The contrast program test correlated with bradykinesia (r = -0.479, p = 0.013) Conclusion: Episodic memory and visuospatial dysfunction, which reflect impairment of the posterior cortical area, are critical cognitive deficits, and memory impairment is correlated with the axial symptoms that are associated with non-dopaminergic pathways in newly diagnosed PD-MCI patients.