The effect of one dry needling session on pain, central pain processing, muscle co-contraction and gait characteristics in patients with knee osteoarthritis: a randomized controlled trial

OBJECTIVES

To assess the immediate and three days postintervention effect of one dry needling session compared to one sham needling session on pain, central pain processing, muscle co-contraction and spatiotemporal parameters during gait in knee osteoarthritis patients.

METHODS

A double-blind randomized controlled trial was conducted. Sixty-one knee osteoarthritis patients were randomly assigned to the dry needling or sham needling group. Primary outcomes were pain and central pain processing. Secondary outcomes included muscle co-contraction and spatiotemporal parameters during gait. Patients were assessed at baseline and 15 min after the intervention, and pain also three days after the intervention. Linear mixed models were used to examine between- and within-group differences.

RESULTS

No significant between-group differences for pain were found, but within-group scores showed a significant decrease 15 min after sham needling and three days after dry needling. The mean conditioned pain modulation effect measured at the m. Trapezius worsened significantly 15 min after sham needling compared to after dry needling (between-group difference). However, individual conditioned pain modulation percentage scores remained stable over time. Various significant within-group differences were found 15 min after sham needling: a decrease of conditioned pain modulation measured at m. Quadriceps and m. Trapezius and stride- and step-time scores, and an increase in step length and widespread pain pressure threshold. A significant decrease in muscle co-contraction index of the m. Vastus Medialis and Semitendinosus was found as within-group difference 15 min after dry needling.

CONCLUSIONS

Dry needling has no larger effect on pain, central pain processing, muscle co-contraction and gait pattern 15 min and three days postintervention compared to sham needling. Mean conditioned pain modulation scores worsened after sham needling compared to after dry needling. Further research remains necessary.

The development of a novel questionnaire assessing alterations in central pain processing in people with and without chronic pain

Background and aims The purpose of this study was to (a) develop and (b) conduct exploratory factor analysis on a novel self-report instrument for symptoms associated with altered central pain processing. Methods We first developed a 25-item questionnaire based on previous literature identifying symptoms and behaviours that may reflect altered spinal and supraspinal pain processing. We then administered this questionnaire to 183 people with chronic pain (n = 99) and healthy individuals (n = 84). Exploratory factor analysis was conducted to identify the factor structure of the questionnaire. Results Our results support a two-factor solution for the 25-item questionnaire that accounted for 57.2% of the total variance of responses in people with and without chronic pain. Factor one (11 items) included items related to alterations in sensation of pain, while factor two (seven items) included items associated with emotional and fatigue symptoms. Seven items showed weak factor loadings and were eliminated. Reliability was excellent, while both factors showed strong correlations with previously-validated self-report Instruments: (pain catastrophising, mood, vigilance, pain self-efficacy) and conditioned pain modulation, providing evidence for their validity. Conclusions We have developed a questionnaire containing two factors that appear to be related to two different symptom clusters, one of which is specifically related to pain and one of which contains other health-related symptoms related to mood and fatigue. These factors show excellent internal consistency and validity. This questionnaire may be a quick, easy and reliable instrument to assess central pain processing in clinical settings.

Replication and extension of the link between the cardiovascular system and sensitivity to social pain in healthy adults

Resting blood pressure (BP) and heart rate variability (HRV) are linked to physical pain. Research also shows a link between social pain and physical pain, and an inverse association between resting BP and social pain. However, little is known regarding the relationship between resting HRV and social pain. Therefore, the present study aimed to replicate the link between social pain and physical pain, and the inverse relationship between resting BP and social pain, and explore the relationship between resting HRV and social pain. One-hundred twenty three healthy adults completed 1) resting cardiovascular measurements of BP and low-frequency (LF) and high-frequency (HF) HRV powers, 2) social pain sensitivity assessment via the Brief Fear of Negative Evaluation (BFNE) and Mehrabian's Sensitivity to Rejection (MSR) scales, and 3) physical pain sensitivity assessment via subjective pain responses during cold pressor test. The results indicated that no association was observed between social pain and physical pain, whereas resting BP was inversely associated with the MSR scores. Resting LF-HRV was inversely associated with social pain, whereas resting HF-HRV was positively associated with social pain. These findings suggest that physical pain and social pain may share biological substrates that are involved in BP regulation and pain control.

Reversal of hyperactive subthalamic circuits differentially mitigates pain hypersensitivity phenotypes in parkinsonian mice

Treatments for pain symptoms in patients with Parkinson’s disease (PD) show inconsistent efficacy across clinical trials, largely owing to our limited understanding of the mechanisms underlying PD pain. Here, we demonstrate that overactivation of subthalamic nucleus (STN) neurons and their projections is adequate to produce a pain hypersensitivity phenotype, and that such overactivation is essential for the hypersensitivity in pain processing pathways and the maintenance of pain hypersensitivity observed in parkinsonian mice. These results suggest that inhibition of STN neurons may be a potential therapeutic strategy for pain relief in PD. Our finding that individual STN projections differentially regulate mechanical and thermal pain thresholds raises the possibility that individual STN projections may be optimal therapeutic targets for different pain phenotypes.

Although pain is a prevalent nonmotor symptom in Parkinson’s disease (PD), it is undertreated, in part because of our limited understanding of the underlying mechanisms. Considering that the basal ganglia are implicated in pain sensation, and that their synaptic outputs are controlled by the subthalamic nucleus (STN), we hypothesized that the STN might play a critical role in parkinsonian pain hypersensitivity. To test this hypothesis, we established a unilateral parkinsonian mouse model with moderate lesions of dopaminergic neurons in the substantia nigra. The mice displayed pain hypersensitivity and neuronal hyperactivity in the ipsilesional STN and in central pain-processing nuclei. Optogenetic inhibition of STN neurons reversed pain hypersensitivity phenotypes in parkinsonian mice, while hyperactivity in the STN was sufficient to induce pain hypersensitivity in control mice. We further demonstrated that the STN differentially regulates thermal and mechanical pain thresholds through its projections to the substantia nigra pars reticulata (SNr) and the internal segment of the globus pallidus (GPi)/ventral pallidum (VP), respectively. Interestingly, optogenetic inhibition of STN-GPi/STN-VP and STN-SNr projections differentially elevated mechanical and thermal pain thresholds in parkinsonian mice. In summary, our results support the hypothesis that the STN and its divergent projections play critical roles in modulating pain processing under both physiological and parkinsonian conditions, and suggest that inhibition of individual STN projections may be a therapeutic strategy to relieve distinct pain phenotypes in PD.