Objective: This paper aims at establishes the presence of significantly higher cholinergic dysfunction in patients using short latency afferent inhibition.

Background: Parkinson’s disease (PD) is a common neurodegenerative disorder associated with a broad spectrum of non-motor symptoms.  Parkinson’s disease (PD) has both motor and non-motor symptoms. RBD is a common pre-motor symptom in PD with highest specificity of any prodromal marker in PD. Previous literature suggests significant differences between patients of PD with and without RBD (PD-RBD, PD-nRBD). Although the role of cholinergic dysfunction in RBD has been described and linked with cognitive impairment, this association has been inadequately explored in PD-RBD. TMS has become a unique tool to assess distinct intracortical circuits in the CNS and indirectly determine the function of neurotransmitters, respectively.

Method: Thirty patients each with PD-RBD, PD without RBD (PD-nRBD) were recruited. Detailed neurological examination was done. RBD was evaluated based on the REM sleep behavior disorder questionnaire (RBDSQ) with score of more than 6. All subjects underwent transcranial magnetic stimulation (TMS) with recording of resting motor threshold (RMT), central motor conduction time (CMCT), silent period (SP), short interval intracortical inhibition (SICI), intracortical facilitation (ICF), short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI). Data was analyzed using R software. Mean and SD was calculated for categorical variables. One way- ANOVA and Pearson’s correlation was performed.

Results: There were significant differences in the PD-RBD and PD-nRBD group. TMS parameters such as ICF, SAI and LAI parameters.

Conclusion: The pathophysiological mechanisms of RBD and origin of the violent movements are still matter of debate. SAI findings along with neuropsychological results support the hypothesis of cholinergic dysfunction in patients of PD with RBD, who will probably develop dementia, and raise the possibility that the presence of RBD may indicate increased risk of cognitive impairment in patients with PD. Longitudinal studies of the patients are required to verify whether SAI abnormalities can predict a future severe cognitive decline. TMS is helpful in finding out cortical excitability and plays an important role in monitoring disease severity.

References: Bhattacharya, Amitabh, et al. “Abnormal Intracortical Functions in Parkinson’s Disease with Rapid Eye Movement Sleep Behaviour Disorder.” Canadian Journal of Neurological Sciences (2021): 1-6.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/exploring-the-impact-of-central-cholinergic-dysfunction-on-cognitive-functioning-in-patients-of-parkinsons-disease-with-and-without-rem-sleep-behavior-disorder/