Objective: Our study aimed to compare the cognitive function depending on the one-sided symptom dominance for investigating association between specific cognitive function and asymmetric motor laterality in Parkinson’s disease(PD).

Background: Our previous study revealed that significant thinning of motor-related cortical areas in contralateral hemisphere to symptomatic side only in left sided PD (LPD) patients. If different cortical thinning areas according to side of symptom dominance and asymmetric dopaminergic depletion are exist, there would be differences in cortical function such as cognitive function depending on symptomatic side.

Methods: We enrolled 67 patients with right-handed PD and they were divided into two groups according to side of symptom onset or predominant motor symptom (right and left). The motor laterality was defined as follow: 1) side of symptom onset, 2) opposite side of dominantly decreased dopamine uptake in positron emission tomography using 18F-N-(3- fluoropropyl)- 2 beta – carbonethoxy – 3 beta – (4 – iodophenyl) nortropane (FP-CIT), and 3) a conjunctive point of high composite scores summing the individual motor items of UPDRS part III (rigidity, bradykinesia, tremor). Right-sided (RPD, 40) and left-sided PD (LPD, 27) patients underwent a neuropsychological battery exploring memory, attention/working memory, frontal/executive, visuospatial and language functions. Student’s t-test and Chi-square test have been carried out to compare clinical and neuropsychological data between two groups.

Results: There were no significant differences of age, gender, duration of education and disease, UPDRS-III and H&Y stage. General cognitive function assessed by K-MMSE and K-MoCA did not show differences between RPD and LPD. The digit forward score was lower in RPD than LPD (5.43±1.49 vs 6.15±1.38). There were no significant differences in digit backward test, memory, language, visouspatial function and frontal/executive function between these patient groups.

Conclusions:  Our study demonstrated that there were no differences in overall cognitive domains depending on side of motor laterality, however RPD had significantly lower scores in the digit span forward than LPD. These data implied that RPD had more impaired verbal fluency and working memory than LPD. We need to consider motor laterality for motor function as well as cognitive impairment in treatment of PD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-association-between-motor-laterality-and-cognitive-impairment-in-parkinsons-disease/