Abstract
Background & ObjectivePain is a common non-motor symptom in Parkinson’s disease. As dopaminergic dysfunction is suggested to affect intrinsic nociceptive processing, this study was designed to characterize laser-induced pain processing in early-stage Parkinson’s disease patients in the dopaminergic OFF state, using a multimodal experimental approach at behavioral, autonomic, imaging levels.Methods13 right-handed early-stage Parkinson’s disease patients without cognitive or sensory impairment were investigated OFF medication, along with 13 age-matched healthy control subjects. Measurements included warmth perception thresholds, heat pain thresholds, and central pain processing with event-related functional magnetic resonance imaging (erfMRI) during laser-induced pain stimulation at lower (E = 440 mJ) and higher (E = 640 mJ) target energies. Additionally, electrodermal activity was characterized during delivery of 60 randomized pain stimuli ranging from 440 mJ to 640 mJ, along with evaluation of subjective pain ratings on a visual analogue scale.ResultsNo significant differences in warmth perception thresholds, heat pain thresholds, electrodermal activity and subjective pain ratings were found between Parkinson’s disease patients and controls, and erfMRI revealed a generally comparable activation pattern induced by laser-pain stimuli in brain areas belonging to the central pain matrix. However, relatively reduced deactivation was found in Parkinson’s disease patients in posterior regions of the default mode network, notably the precuneus and the posterior cingulate cortex.ConclusionOur data during pain processing extend previous findings suggesting default mode network dysfunction in Parkinson’s disease. On the other hand, they argue against a genuine pain-specific processing abnormality in early-stage Parkinson’s disease. Future studies are now required using similar multimodal experimental designs to examine pain processing in more advanced stages of Parkinson’s disease.
Highlights
Parkinson’s disease (PD) is a neurodegenerative disorder causing progressive deterioration of motor function [1]
No significant differences in warmth perception thresholds, heat pain thresholds, electrodermal activity and subjective pain ratings were found between Parkinson’s disease patients and controls, and event-related functional magnetic resonance imaging (erfMRI) revealed a generally comparable activation pattern induced by laser-pain stimuli in brain areas belonging to the central pain matrix
He is a member of the Advisory Boards of Allergan, Ipsen Pharma and Merz Pharmaceuticals
Summary
Parkinson’s disease (PD) is a neurodegenerative disorder causing progressive deterioration of motor function [1]. Pain in PD is under recognized and undertreated [13], affecting roughly 40–60% of PD patients [5,6,13,14,15,16,17,18,19], and is linked to depression, decreased quality of life [20], female gender, age, disease duration and severity [16]. A study involving 176 home-living PD patients [13] found elevated pain levels on the ‘Bodily Pain Scale’, with musculoskeletal pain making up 70%, followed by dystonic pain (40%), radicular-neuropathic pain (20%), and central neuropathic pain (10%). Pain is a common non-motor symptom in Parkinson’s disease. As dopaminergic dysfunction is suggested to affect intrinsic nociceptive processing, this study was designed to characterize laser-induced pain processing in early-stage Parkinson’s disease patients in the dopaminergic OFF state, using a multimodal experimental approach at behavioral, autonomic, imaging levels
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