Aim to examine the severity of executive dysfunction among different Parkinson's disease (PD)-mild cognitive impairment (MCI) subtypes in the early stages of the disease. The final sample consisted of 65 patients with mild PD progression. Based on neuropsychological measures, our sample was categorized into three PD-MCI subtypes: (1) PD-MCI executive group (n = 24), (2) PD-MCI executive plus memory group (n = 22), and (3) PD-MCI executive plus visuospatial group (n = 19). Patients' executive functions were evaluated with the Trail Making Test-Part B (TMT-B) and Stroop Neuropsychological Screening Test (SNST) for mental flexibility and inhibitory control, respectively. One-way ANOVA results indicated significant differences among the three subgroups on TMT-B and SNST performance. Post hoc Tukey honestly significant different (HSD) tests revealed that the PD-MCI executive plus visuospatial group had lower performances on both executive measures than the other two groups. Contrastingly, no significant differences were observed between the PD-MCI executive group and PD-MCI executive plus memory group. Our results indicated that the severity of executive dysfunction varies across different PD-MCI subtypes. These findings are discussed within the framework of the dual syndrome hypothesis and highlight the utility of determination of executive impairment severity for effective clinical management of patients with PD.
Keywords: Executive functions; Parkinson’s disease; inhibitory control; mental flexibility; mild cognitive impairment.