Objective: To clarify the functional role of sensorimotor cortex in Parkinson’s disease (PD)-related pain.

Background: Pain is one of the most common nonmotor symptoms in PD. Currently it is feasible to separate PD-related pain from PD-unrelated pain. However, the pathophysiology of the PD-related pain remains unclear.

Method: Twenty PD patients were recruited and assigned to two groups: 8 (aged 67.1±7.1 years, 5 women) with PD-related pain and 12 (aged 66.3±7.3 years, 5 women) without PD-related pain. There was no significant difference in age and disease severity between the two groups. Patients received a series of clinical assessments including Unified Parkinson’s Disease Rating Scale (UPDRS), Parkinson’s Disease Pain Classification System, Brief Pain Inventory, Beck Anxiety and Depression Inventory, Quality of Life in PD Questionnaire. Resting-state functional magnetic resonance imaging was also performed. The physiological biomarkers for the excitability of sensorimotor cortex, including the input-output curve of magnetic evoked potentials, intracortical facilitation and inhibition, short afferent inhibition and somatosensory evoked potentials, were also measured.

Results: The PD with related pain group showed a significantly higher score of the second part, the fourth part and the total score of UPDRS than that in the PD without related pain group. The Brief Pain Inventory, Beck Anxiety and Depression Inventory also revealed that the PD with related pain group had a significantly higher score than that in the PD without related pain group. The functional magnetic resonance imaging showed that the functional connectivity between the bilateral amygdala in limbic system and the extensive brain areas was significantly different between the two groups. Examination of the physiological biomarkers representing sensorimotor cortical activities did not show any significant difference between the two groups.

Conclusion: The current findings suggest that PD-related pain may associate to the limbic system rather than simply relate to the neural activity of the sensorimotor cortex. Further studies focusing in the limbic system would be necessary to clarify the pathophysiology of PD-related pain.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cortical-excitability-of-sensorimotor-cortex-in-parkinsons-disease-related-pain/