Parkinson's disease patients with pain suffer from more severe non-motor symptoms.

Non-motor symptoms, including pain, depression, sleep disorder, and olfactory dysfunction, occur frequently in patients with Parkinson's disease (PD), even before the onset of motor symptoms. Although studies have examined the correlation between pain and depression or sleep disorder in PD, few studies have investigated the correlation between pain and a range of other non-motor symptoms of PD. PD patients (n = 142) with or without pain were included in the study. PD severity was evaluated with the Unified Parkinson's Disease Rating Scale (UPDRS) and the Hoehn and Yahr (H/Y) staging scale. Pain severity was analyzed with the Visual Analog Scale. The Hamilton Rating Scale for Depression (HRSD; 24 items), Montreal Cognitive Assessment Beijing Version (MoCA), and non-motor questionnaire (NMSQT) measured symptoms of depression, cognitive function, and non-motor symptoms. The incidence of pain was 47.9% in patients with PD, most of whom had moderate pain levels. Patients with pain showed higher HRSD, UPDRS, H/Y, and NMSQT scores and lower MoCA scores compared to those of patients without pain. HRSD and NMSQT scores were closely related with pain (P < 0.001). Non-motor symptoms were more prominent in patients with pain compared to that of controls and PD patients without pain.

Quantitative and fiber-selective evaluation of pain and sensory dysfunction in patients with Parkinson's disease.

INTRODUCTION: Pain and sensory disturbances affect many patients with Parkinson's disease (PD). The present study aimed to evaluate the pain and sensory sensitivity of each class of afferent fibers in PD patients and determine the effects of dopaminergic therapy on pain and sensory sensitivity. METHODS: Current perception threshold (CPT) and pain tolerance thresholds (PTT) at three frequencies, 2000 Hz, 250 Hz, and 5 Hz, to stimulate Aß fibers, Aδ fibers, and small C-polymodal fibers, respectively, were measured in 72 PD patients and 35 healthy controls. RESULTS: CPT was higher at all three frequencies and PTT was lower at 2000 Hz and 250 Hz in PD patients with pain versus healthy controls (P < 0.05). CPT was higher at 2000 Hz and 250 Hz and PTT was lower at 2000 Hz and 250 Hz in PD patients without pain versus healthy controls (P < 0.05). PD patients with pain exhibited higher CPT at 5 Hz and 250 Hz than PD patients without pain (P < 0.05). Dopaminergic therapy did not affect CPT or PPT in PD patients (P > 0.05). CONCLUSIONS: Abnormal Aδ fiber- and Aß fiber-dependent sensory inputs may exist in PD. Abnormal sensory inputs via C fibers and Aδ fibers might be associated with the presence of pain in PD. Because dopaminergic therapy failed to mitigate these sensory and pain dysfunctions, mechanisms not involving the dopaminergic pathway are likely to be implicated.