Abstract A significant proportion of patients with knee osteoarthritis (OA) continue to have severe ongoing pain following knee replacement surgery. Central sensitization and features suggestive of neuropathic pain before surgery may result in a poor outcome post-operatively. In this prospective observational study of patients undergoing primary knee arthroplasty (n=120), the modified PainDETECT score was used to divide patients, with primary knee OA, into nociceptive (<13), unclear (13–18) and neuropathic -like pain (>18) groups pre-operatively. Response to surgery was compared between groups using the Oxford Knee Score (OKS) and the presence of moderate to severe long-term pain 12 months after arthroplasty. The analyses were replicated in a larger independent cohort study (n=404). 120 patients were recruited to the main study cohort: 63 (52%) nociceptive pain; 32 (27%) unclear pain; 25 (21%) neuropathic-like pain. Patients with neuropathic-like pain had significantly worse OKS pre and post-operatively, compared to the nociceptive pain group, independent of age, sex and BMI. At 12-months post-operatively the mean OKS was 4 points lower in the neuropathic-like group compared with the nociceptive group in the study cohort (non-significant); with a difference of 5 points in the replication cohort (p<0.001). Moderate to severe long-term pain after arthroplasty at 12-months was present in 50% of the neuropathic-like pain group versus 24% in the nociceptive pain group, in the replication cohort (p<0.001). Neuropathic pain is common and targeted therapy pre, peri and post-operatively may improve treatment response.
Abstract Background IMI2-PainCare-BioPain-RCT2 is one of four similarly designed clinical studies aiming at profiling a set of functional biomarkers of drug effects on specific compartments of the nociceptive system that could serve to accelerate the future development of analgesics. IMI2-PainCare-BioPain-RCT2 will focus on human spinal cord and brainstem activity using biomarkers derived from non-invasive neurophysiological measurements. Methods This is a multisite, single-dose, double-blind, randomized, placebo-controlled, 4-period, 4-way crossover, pharmacodynamic (PD) and pharmacokinetic (PK) study in healthy subjects. Neurophysiological biomarkers of spinal and brainstem activity (the RIII flexion reflex, the N13 component of somatosensory evoked potentials (SEP) and the R2 component of the blink reflex) will be recorded before and at three distinct time points after administration of three medications known to act on the nociceptive system (lacosamide, pregabalin, tapentadol), and placebo, given as a single oral dose in separate study periods. Medication effects on neurophysiological measures will be assessed in a clinically relevant hyperalgesic condition (high-frequency electrical stimulation of the skin), and in a non-sensitized normal condition. Patient-reported outcome measures (pain ratings and predictive psychological traits) will also be collected; and blood samples will be taken for pharmacokinetic modelling. A sequentially rejective multiple testing approach will be used with overall alpha error of the primary analysis split between the two primary endpoints, namely the percentage amplitude changes of the RIII area and N13 amplitude under tapentadol. Remaining treatment arm effects on RIII, N13 and R2 recovery cycle are key secondary confirmatory analyses. Complex statistical analyses and PK-PD modelling are exploratory. Discussion The RIII component of the flexion reflex is a pure nociceptive spinal reflex widely used for investigating pain processing at the spinal level. It is sensitive to different experimental pain models and to the antinociceptive activity of drugs. The N13 is mediated by large myelinated non-nociceptive fibers and reflects segmental postsynaptic response of wide dynamic range dorsal horn neurons at the level of cervical spinal cord, and it could be therefore sensitive to the action of drugs specifically targeting the dorsal horn. The R2 reflex is mediated by large myelinated non-nociceptive fibers, its circuit consists of a polysynaptic chain lying in the reticular formation of the pons and medulla. The recovery cycle of R2 is widely used for assessing brainstem excitability. For these reasons, IMI2-PainCare-BioPain-RCT2 hypothesizes that spinal and brainstem neurophysiological measures can serve as biomarkers of target engagement of analgesic drugs for future Phase 1 clinical trials. Phase 2 and 3 clinical trials could also benefit from these tools for patient stratification. Trial registration This trial was registered on 02 February 2019 in EudraCT ( 2019-000755-14 ).
ABSTRACT Effective management of distressing bodily symptoms (such as pain and breathlessness) is an important clinical goal. However, extensive variability exists in both symptom perception and treatment response. One theory for understanding variability in bodily perception is the ‘Bayesian Brian Hypothesis’, whereby symptoms may result from the combination of sensory inputs and prior expectations. In light of this theory, we explored the relationships between opioid responsiveness, behavioural/physiological symptom modulators and brain activity during anticipation of breathlessness. Methods We utilised two existing opioid datasets to investigate the relationship between opioid efficacy and physiological/behavioural qualities, employing hierarchical cluster analyses in: 1) a clinical study in chronic obstructive pulmonary disease, and 2) a functional magnetic resonance brain imaging study of breathlessness in healthy volunteers. We also investigated how opioid efficacy relates to anticipatory brain activity using linear regression in the healthy volunteers. Results Consistent across both datasets, diminished opioid efficacy was more closely associated with negative affect than with other physiological and behavioural properties. Furthermore, in healthy individuals, brain activity in the anterior cingulate and ventromedial prefrontal cortices during anticipation of breathlessness were inversely correlated with opioid effectiveness. Conclusion Diminished opioid efficacy for relief of breathlessness may be associated with high negative affective qualities, and was correlated with the magnitude of brain activity during anticipation of breathlessness. Clinical implications Negative affect and symptom expectations may influence perceptual systems to become less responsive to opioid therapy.
Abstract Background/Aims Features of centralised pain, encompassing widespread pain and non-pain features such as multisensory hypersensitivity, fatigue, and sleep disturbance are common in RA. We hypothesise that centralised pain in early RA affects response to standard first-line treatment. Methods Prospective cohort study of adults with a clinical diagnosis of RA recruited from the early inflammatory arthritis clinic, Oxford University Hospitals, who completed an online assessment within two weeks of starting a DMARD. Centralised pain was assessed using three measures: the 2016 Fibromyalgia Survey Criteria (0-31), Central Sensitisation Inventory (CSI, 0-100), and PainDetect (0-38). The primary outcome, bodily pain, was assessed using the Short Form-36 Bodily Pain Scale (BPS), where lower scores indicate worse pain severity. During follow-up, participants completed three sets of follow-up questionnaires at 3-, 6- and 12-months. Linear mixed effects models were used to account for repeated measurements and patient variability. Three models were fitted, for an association between baseline values of each centralised pain measure with BPS over time. An interaction between centralised pain scores with time was fitted to assess for effect of the exposure on change over time. Age, sex, and symptom duration at baseline were included as confounding variables. Ethical approval was granted by South Central Oxford B Research Ethics Committee. Results Of 149 participants, 117 (79%) completed follow-up: median (IQR) age 59.8 (24.6) years; 36% male; 30% with symptoms >1 year at baseline. There were no significant baseline differences among those lost to follow-up, apart from a longer symptom duration (53% vs 30% symptom duration >1 year; P = 0.033). At baseline, median (IQR) Fibromyalgia Survey Criteria, CSI, and PainDetect scores were 12 (6), 36 (17), and 14 (9) respectively. The median (IQR) BPS at baseline was 32.5 (22.5). Measures of centralised pain were moderately-to-strongly correlated with each other, and with BPS. Individuals with symptoms for >1 year had higher scores on the PainDetect (P = 0.0015), but not the CSI (P = 0.0545) or Fibromyalgia Survey Criteria (P = 0.672). After adjusting for age, sex, and symptom duration, there was a significant association between centralised pain at baseline and BPS over follow-up, e.g.; for every unit increase in the fibromyalgia survey criteria at baseline, the BPS decreased by 2.40 (95%CI -3.29, -1.49; P < 0.001) points over follow-up. Similar relationships were seen with the CSI and PainDetect scores. Conclusion Centralised pain measures in early RA patients can be indicative of the severity of bodily pain experienced during the subsequent 12 months after starting a DMARD treatment. Recognising and assessing centralised pain in early RA patients may enable us to tailor more effective and individualised treatment regimens. Further studies, especially those utilising neuroimaging and QST, are essential to elucidate the neural mechanisms underlying the impact of centralised pain on treatment outcomes in RA. Disclosure E. Kelleher: None. A.J. Wall: None. M.T. Sanchez-Santos: None. V. Wanigasekera: None. A. Irani (nee Soni): None.
Abstract The neural mechanisms underlying placebo analgesia have attracted considerable attention over the recent years. In contrast, little is known about the neural underpinnings of a nocebo‐induced increase in pain. We previously showed that nocebo‐induced hyperalgesia is accompanied by increased activity in the hippocampus that scaled with the perceived level of anxiety. As a key node of the neural circuitry of perceived threat and fear, the hippocampus has recently been proposed to coordinate defensive behaviour in a context‐dependent manner. Such a role requires close interactions with other regions involved in the detection of and responses to threat. Here, we investigated the functional connectivity of the hippocampus during nocebo‐induced hyperalgesia. Our results show an increase in functional connectivity between hippocampus and brain regions implicated in the processing of sensory‐discriminative aspects of pain (posterior insula and primary somatosensory/motor cortex) as well as the periaqueductal grey. This nocebo‐induced increase in connectivity scaled with an individual's increase in anxiety. Moreover, hippocampus connectivity with the amygdala was negatively correlated with the pain intensity reported during nocebo hyperalgesia relative to the placebo condition. Our findings suggest that the hippocampus links nocebo‐induced anxiety to a heightened responsiveness to nociceptive input through changes in its crosstalk with pain‐modulatory brain areas.
An individual’s expectation that a pain treatment will or will not work can alter both its subjective effectiveness and the pain-related activity in the brain.
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