Curcumin analogue NL04 inhibits spinal cord central sensitization in rats with bone cancer pain by inhibiting NLRP3 inflammasome activation and reducing IL-1β production

The management and therapy of bone cancer pain (BCP) remain formidable clinical challenges. Curcumin and its analogues have been shown to have anti-inflammatory and analgesic properties. In the present study, we investigated the efficacy of curcumin analogue NL04 (NL04) in modulating inflammation in spinal dorsal horn (SDH), thereby exploring its potential to reduce central sensitization of BCP in a rat model. Differing doses of NL04 and curcumin were administered intrathecally either once (on day 12 of BCP) or over seven consecutive days (from day 6-12 of BCP). Results indicated that the ED50 for NL04 and curcumin ameliorating BCP-induced mechanical hyperalgesia is 49.08 μg/kg and 489.6 μg/kg, respectively. The analgesic effects at various doses of NL04 lasted between 4 and 8 h, with sustained administration over a week maintaining pain relief for 1-4 days, while also ameliorating locomotor gait via gait analysis and reducing depressive and anxiety-like behaviors via open-field and light-dark transition tests. The analgesic effects at various doses of curcumin lasted 4 h, with sustained administration over a week maintaining pain relief for 0-2 days. ELISA, Western blotting, qPCR, and immunofluorescence assays substantiated that intrathecal administration of NL04 on days 6-12 of BCP dose-dependently lowered spinal IL-1β and IL-18 levels and significantly reduced the expression of IKKβ genes and proteins, as well as the downstream cleavage of the trans-Golgi network (TGN). Whole-cell patch-clamp results demonstrated that NL04 inhibits potassium ion efflux in rat primary spinal neurons. Thus, NL04 exhibits significant analgesic effects in a BCP rat model by downregulating IKKβ expression and inhibiting neuronal potassium ion efflux, which, in turn, suppresses the activation of NLRP3 inflammasomes and reduces IL-1β production, potentially ameliorating pain management in BCP.

The effect of balance exercises on central sensitization in patients with knee osteoarthritis

The aim of this study was to evaluate the effectiveness of balance exercises on functional status, pain, balance, and central sensitization in patients with knee osteoarthritis (OA). Patients diagnosed with bilateral Kellgren-Lawrence grade ≥ 2 primary knee OA and associated central sensitization were included in the study. Patients were randomized into two groups. Both groups were provided with verbal and written information on knee OA. In addition, the intervention group received a supervised balance exercise program for 6 weeks, 3 days a week on alternating days. The outcome measures were the changes in the Central Sensitization Inventory (CSI), Visual Analog Scale (VAS) pain, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Berg Balance Scale, and Y Balance Test. Evaluations were performed at baseline, immediately after treatment (6th week) and at 12th week. The study included 40 patients, 20 patients in each group. At the end of the treatment period (6th week), the improvement in CSI score, WOMAC pain, WOMAC physical function, WOMAC total score, Y Balance Test scores, and VAS pain during activity was significantly greater in the intervention group than that in the control group (p < 0.001). Regarding the changes from baseline to the 12th week, the intervention group experienced greater improvement in most of the outcome measures. Yet, the change in WOMAC pain score, Berg Balance Scale score, and VAS pain at rest was similar between the study groups (p = 0.05, p = 0.257, and p = 0.385, respectively). A two-model multiple linear regression analysis revealed that the changes in VAS pain (during activity) after the treatment and at follow-up [(p = 0.004, adjusted R2: 0.346) and (p = 0.002, adjusted R2: 0.391), respectively], as well as changes in WOMAC pain from baseline to follow-up (p = 0.020, ΔR2 = 0.245) significantly affected central sensitization. However, changes in Y Balance Test and WOMAC total scores did not appear to have a significant impact on the improvement in central sensitization (p > 0.05). Balance exercises may provide improvement in central sensitization, functional status, and dynamic balance among patients with knee OA. The improvement in central sensitization depends mostly on the pain relief effect of balance exercises.

Central Sensitization: The Missing Link Between Psychological Distress and Poor Outcome Following Primary Total Knee Arthroplasty

BACKGROUND

While preoperative psychological distress is known to predict risk for worse total knee arthroplasty (TKA) outcomes, distress may be too broad and nonspecific a predictor in isolation. We tested whether there are distinct preoperative TKA patient types based jointly on psychological status and measures of altered pain processing that predict adverse clinical outcomes.

METHODS

In 112 TKA patients, we preoperatively assessed psychological status (depression, anxiety, and catastrophizing) and altered pain processing via a simple quantitative sensory testing protocol capturing peripheral and central pain sensitization. Outcomes (pain, function, opioid use) were prospectively evaluated at 6 weeks and 6 months after TKA. Cluster analyses were used to empirically identify TKA patient subgroups.

RESULTS

There were 3 distinct preoperative TKA patient subgroups identified from the cluster analysis. A low-risk (LR) group was characterized by low psychological distress and low peripheral and central sensitization. In addition, 2 subgroups with similarly elevated preoperative psychological distress were identified, differing by pain processing alterations observed: high-risk centralized pain and high-risk peripheral pain. Relative to LR patients, high-risk centralized pain patients displayed significantly worse function and greater opioid use at 6 months after TKA (P values <.05). The LR and high-risk peripheral pain patient subgroups had similar 6-month outcomes (P values >.05).

CONCLUSIONS

Among patients who have psychological comorbidity, only patients who have central sensitization were at elevated risk for poor functional outcomes and increased opioid use. Central sensitization may be the missing link between psychological comorbidity and poor TKA clinical outcomes. Preoperative testing for central sensitization may have clinical utility for improving risk stratification in TKA patients who have psychosocial risk factors.

Association between central sensitization, pain sensitivity and balance control in patients with migraine

BACKGROUND

Balance alterations are prevalent among pain conditions, including migraine. The mechanisms explaining the association between pain and balance are unclear, as well as whether levels of pain sensitivity correlate with impaired balance. Our aim was therefore to investigate the association between balance, central sensitization symptoms and pain sensitivity in patients with migraine.

METHODS

This cross-sectional study included 50 patients and demographic, clinical information, central sensitization inventory (CSI) and pain catastrophizing (PCS) scores were obtained. Patients underwent a standardized protocol evaluating balance and pain thresholds for cold (CPT), heat (HPT), mechanical (MPT) and pressure (PPT) in trigeminal (V1) and extra-trigeminal (C6) dermatomes. Data were analysed using Person's correlation, linear regression models and contrasting the presence and absence of central sensitization symptoms through T-tests.

RESULTS

Mild-to-moderate correlations were observed between balance and MPT in V1 (r = -0.24, p = 0.046) and C6 (r = -0.41, p = 0.002), CPT in V1 (r = 0.31, p = 0.026), CSI scores (r = 0.27, p = 0.029) and migraine frequency (r = 0.25, p = 0.040). Balance was explained by CPT and MPT (R2 = 0.32, p = 0.001). The variance of CSI was explained by PCS scores and balance (R2 = 0.28, p = 0.001). Patients with symptoms of central sensitization presented an increased balance impairment (p = 0.044) and higher catastrophizing levels (p = 0.001) in contrast to patients without symptoms.

CONCLUSION

Balance impairment is associated with reduced pain thresholds and higher CSI scores. These results may help to elucidate the aetiology of balance alterations among chronic pain conditions.

SIGNIFICANCE

For the first time, it has been shown that balance alterations can reflect greater pain sensitivity and signs of central sensitization in patients with migraine. This opens up perspectives for future studies to understand the mechanisms and further factors associated with balance and pain sensitivity in migraine.

The effect of joint position sense therapy on chronic shoulder pain with central sensitization

BACKGROUND

Chronic shoulder pain is a common musculoskeletal problem associated with unreleased pain and functional dysfunction that can evolve into central sensitization. Some forms of manual therapy may exacerbate pain and central sensitization. This study investigated the impact of joint position sense therapy (JPST), a moderate joint proprioception training technique, on central sensitization, shoulder functional dysfunction, and pain in patients with chronic shoulder pain compared with more intense exercises or aggressive manual therapies.

METHODS

We assessed the pressure pain threshold (PPT) in 30 patients with and 30 patients without chronic shoulder pain. The assessment focused on 4 muscle sites: deltoid, upper trapezius, brachioradialis, and tibialis anterior. Thirty patients with chronic shoulder pain were randomly divided into the JPST and control groups. The JPST group underwent additional shoulder joint position-sense training. The efficiency outcomes were the disabilities of the arm, shoulder, and hand questionnaire, visual analog scale (VAS), and PPT, evaluated at baseline and after the intervention.

RESULTS

Significant differences were observed in the PPT values at the brachioradialis (P < .05), deltoid (P < .01), and trapezius (P < .001) among the non-chronic and chronic groups, but not in the tibialis anterior muscle (P > .05). Although both control and JPST interventions effectively improved the disabilities of the arm, shoulder, and hand questionnaire score, pain intensity, and PPT values in the upper limb, the outcomes in the JPST group were significantly different from those in the control group.

CONCLUSIONS

Generalized hyperalgesia changes limited to the upper limbs were observed in patients with chronic shoulder pain. JPST has beneficial effects on pain control and functional dysfunction in patients with chronic shoulder pain.

Association between smoking and central sensitization pain: a web-based cross-sectional study

PURPOSE

This study aimed to investigate whether smoking is an independent risk factor for central sensitization syndrome (CSS) in individuals with pain as measured by the Central Sensitization Inventory (CSI).

METHODS

In 2020, we conducted an Internet survey targeting 2000 ordinary residents of Japan (aged 20-69 years) who had pain symptoms from October to November 2020. A multiple regression analysis was performed on the association between smoking status (nonsmokers and current smokers; Brinkman index) and CSI values. Moreover, compared to nonsmokers, the relative risk (RR) of the CSI cut-off score of 40 points or higher among current smokers was calculated using a modified Poisson regression model. Covariates included age, sex, body mass index, marital status, equivalized income, exercise habits, history of hypertension, history of hyperlipidemia, history of diabetes, pain chronicity, and Pain Catastrophizing Scale score.

RESULTS

This study analyzed 1,822 individuals (1,041 men and 781 women). Among those experiencing pain, current smoking was associated with the increase in CSI values (β = 0.07). The Brinkman index was also significantly associated with the increase in CSI values (β = 0.06). Current smoking also increased the risk of being over the CSI cut-off score, with a relative risk (RR) of 1.29 (95% confidence intervals, 1.04-1.60). Younger age, being women, experiencing chronic pain, and higher pain catastrophizing thinking were also significantly associated with increased CSS severity, independent of smoking status.

CONCLUSION

Smoking is an independent risk factor for CSS. This indicates that smoking may be an important factor in the management of central pain disorders.

Relationship Between Central Sensitization-Related Symptoms and Pain-Related Disability After Cervical Spine Surgery: A Structural Equation Model

BACKGROUND

It is unknown if central sensitization (CS)-related symptoms have an intermediate role that might explain how disability develops from pain after cervical spinal surgery.

AIMS

The study aim was to investigate the role of CS-related symptoms in the relationship between pain and disability reported after cervical spinal surgery.

DESIGN

Cross-sectional study.

SETTINGS

Tertiary care spinal surgery center.

PARTICIPANTS/SUBJECTS

The participants included individuals with a cervical degenerative condition who had undergone surgery.

METHODS

The following patient-reported outcome measures were evaluated: (1) Numerical Rating Scale; (2) Neck Disability Index; and (3) Short Form of the Central Sensitization Inventory. A hypothesized model containing the CS-related symptoms and the relationships between pain and disability was constructed and tested by structural equation modeling.

RESULTS

Questionnaires were mailed to 280 individuals, and responses were obtained from 145 participants. Of these respondents, 99 (68.3%) were males and 46 (31.7%) were females, with a mean age of 64.4 ± 12.3 years. The latent variable for pain, represented by the neck (coefficient: 0.856, p < .001) and upper limb pain (0.568, p < .001), influenced CS-related symptoms (coefficient: 0.504, p < .001). Pain directly affected disability (coefficient: 0.497, p < .001) and indirectly through CS-related symptoms. Bootstrap analysis confirmed this indirect effect (point estimate: 2.85, 95% confidence interval: 1.04 to 6.30, p = .04).

CONCLUSIONS

The results revealed that neck and upper limb pain affected disabilities both directly and through CS-related symptoms. Future research should focus on the efficacy of biopsychosocial approaches for patients after cervical spine surgery with a high risk of disability due to CS-related symptoms.

5-HT3a receptor contributes to neuropathic pain by regulating central sensitization in a rat with brachial plexus avulsion

PURPOSE

As a frequently occurring complication resulting from brachial plexus avulsion (BPA), neuropathic pain significantly impacts the quality of life of patients and places a substantial burden on their families. Recent reports have suggested that the 5-HT3a receptor may play a role in the development and regulation of neuropathic pain. The current study aimed to explore the involvement of the 5-HT3a receptor in neuropathic pain resulting from BPA in rats.

METHODS

A rat model of neuropathic pain was induced through brachial plexus avulsion (BPA). The pain thresholds of the rats were measured after BPA. The spinal dorsal horn (SDH) of rats was collected at day 14 after surgery, and the expression and distribution of the 5-HT3a receptor were analyzed using immunohistochemistry and western blotting. The expression levels of various factors related to central sensitization were measured by western blot, including c-Fos, GFAP, IBA-1, IL-1β and TNF-α. The effects of 5-HT3a receptor antagonists on hyperalgesia were assessed through behavioral tests after intrathecal administration of ondansetron. Additionally, at 120 min postinjection, the SDH of rats was acquired, and the change of expression levels of protiens related to central sensitization were measured by western blot.

RESULTS

BPA induced mechanical and cold hypersensitivity in rats. The 5-HT3a receptor was increased and mainly distributed on neurons and microglia in the SDH after BPA, and the level of central sensitization and expression of inflammatory factors, such as c-Fos, GFAP, IBA-1, IL-1β and TNF-α, were also increased markedly. Ondansetron, which is a selective 5-HT3a receptor antagonist, reversed the behavioral changes caused by BPA. The antagonist also decreased the expression of central sensitization markers and inflammatory factors.

CONCLUSION

The results suggested that the 5-HT3a receptor is involved in neuropathic pain by regulating central nervous system sensitization in a rat brachial plexus avulsion model. Targeting the 5-HT3a receptor may be a promising approach for treating neuropathic pain after brachial plexus avulsion.

Black box in overactive bladder: Central sensitization and its relationship with urinary symptom severity and quality of life

AIM

To examine central sensitization (CS), and to investigate the relationship between CS, and urinary symptom severity, and quality of life (QoL) in women with overactive bladder (OAB).

MATERIALS AND METHODS

A total of 144 women with OAB included the study. CS with the Central Sensitization Inventory (CSI), urinary symptom with the Overactive Bladder Questionnaire-Version 8 (OAB-V8), bladder diary and Patients' Perception of Intensity of Urgency Scale (PPIUS) and QoL with the King's Health Questionnaire (KHQ) were assessed.

RESULTS

It was found that 47.9% (n = 69) of women with OAB had CS. It was observed that the CSI score was related to the OAB-V8 score (ρ = 0.327; p < 0.001) and the average number of voids/day (ρ = 0.291; p < 0.001). Additionally, urgency severity was higher in women with OAB with CS than in women with OAB without CS (p = 0.006). There was a relationship between the CSI score and KHQ-incontinence impact (ρ = 0.250; p = 0.012), KHQ-personal relationship (ρ = 0.253; p = 0.002), KHQ-sleep/energy (ρ = 0.180; p = 0.031), KHQ-emotional state (ρ = 0.310; p < 0.001) and KHQ-severity measurement scores (ρ = 0.391; p < 0.001).

CONCLUSION

In this study, it was observed that the majority of women with OAB had CS. It was found that more severe symptoms of CS were associated with worse urinary symptom severity and QoL in these patients. It may be beneficial to evaluate CS in the management of OAB and to consider CS when determining treatment strategies.

Application of a Clinical Approach to Diagnosing Primary Pain: Prevalence and Correlates of Primary Back and Neck Pain in a Community Physiatry Clinic

Chronic back or neck pain (CBNP) can be primary (nociplastic or neuroplastic; without clear peripheral etiology) or secondary (to nociceptive or neuropathic causes). Expanding on available models of nociplastic pain, we developed a clinic-ready approach to diagnose primary/nociplastic pain: first, a standard physical exam and review of imaging to rule out secondary pain; and second, a detailed history of symptom presentation to rule in primary pain. We trained a physician who evaluated 222 patients (73.9% female, age M = 59.6) with CBNP; patients separately completed pain and psychosocial questionnaires. We estimated the prevalence of primary CBNP and explored biomedical, imaging, and psychological correlates of primary CBNP. Although almost all patients (97.7%) had at least 1 spinal anomaly on imaging, the diagnostic approach estimated that 88.3% of patients had primary pain, 5.0% had secondary pain, and 6.8% had mixed pain. Patients with primary pain were more likely than the other 2 groups of patients (combined as "non-primary pain") to report certain functional conditions, central sensitization, and features such as sensitivity to light touch, spreading pain, and pain worsening with stress; however, no difference was detected in depression, anxiety, and pain catastrophizing between those with primary and nonprimary pain. These findings are consistent with prior estimates that 85 to 90% of CBNP is "nonspecific." Further research is needed to validate and perhaps refine this diagnostic approach, which holds the potential for better outcomes if patients are offered treatments targeted to primary pain, such as pain neuroscience education and several emerging psychological therapies. PERSPECTIVE: We developed an approach to diagnose chronic primary pain, which was applied in a physiatry clinic to 222 patients with CBNP. Most patients (88.3%) had primary pain, despite almost universal anomalies on spinal imaging. This diagnostic approach can guide educational and psychological treatments tailored for primary pain.

Questionnaires for the Assessment of Central Sensitization in Endometriosis: What Is the Available Evidence? A Systematic Review with a Narrative Synthesis

It has been suggested that central sensitization (CS) may be involved in the failure of standard medical and surgical treatment to relieve endometriosis-related pain. However, there is no gold standard for the diagnosis of CS, and self-reported questionnaires are used as diagnostic surrogates. The main objective of this review was to identify all CS questionnaires used in clinical endometriosis studies. The secondary objective was to qualitatively analyze strengths and weaknesses of each questionnaire. A PubMed and EMBASE systematic literature search conducted in April 2023 using the terms "endometriosis; central pain; central sensitization; questionnaire; patient-reported outcome measure; screening tool" identified 122 publications: six articles were included in the review. The Central Sensitization Inventory (CSI) is the most frequently used questionnaire for the detection of CS in patients with endometriosis. It has been validated in patients with endometriosis, in whom it appears to have good psychometric proprieties. The Fibromyalgia Survey Questionnaire (FSQ) has also been used, although it has not been specifically validated in endometriosis patients. The debate regarding these questionnaires' construct validity is still open and will be so until a gold standard diagnostic tool for CS is found. In fact, some authors argue these questionnaires are measuring psychological vulnerability and a hypervigilant state that is associated with pain, rather than CS itself. However, their use should not be discouraged as they are able to identify chronic pain patients which warrant further attention and who may benefit from broader treatment strategies.

The Effect of Central Sensitization on Postoperative Neurocognitive Dysfunction in Hospitalized Elderly Patients: A Prospective Cohort Clinical Trial

OBJECTIVE

To investigate whether central sensitization (CS) in elderly patients was a predictive risk factor for postoperative neurocognitive dysfunction (PNCD).

METHODS

One hundred and thirty-three aged patients undergoing total knee arthroplasty (TKA) who received femoral nerve block and general anesthesia were recruited in this research and prospectively assigned into two groups according to the Central Sensitization Inventory (CSI) score: group C (n = 106, CSI score less than 40) and group CS (n = 27, CSI score higher than 40). Scores of Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE), Confusion Assessment Method (CAM), Numerical Rating Scale (NRS) and Quality of recovery-40 (QoR-40) questionnaires were assessed. Basic information and clinical records of all participants were also collected.

RESULTS

PNCD occurred in 24 (22.6%) of patients in group C and 16 (59.3%) in group CS (p < .05). Multivariate logistic regression analysis revealed that patients with CSI score ≥40 before surgery exhibited higher risk of PNCD after adjustment for other risk factors (p < .05). Compared to group C, the pre- and post-operative NRS scores, pain duration, the WOMAC score, and propofol consumptions for anesthesia induction were significantly increased in group CS (p < .05).

CONCLUSION

Hospitalized elderly patients with clinical symptoms of CS scores may have increased risk of PNCD following TKA.

Characterizing clinical progression in patients with musculoskeletal pain by pain severity and central sensitization-related symptoms

Central sensitization-related symptoms (CSS) are associated with the severity and progression of pain. The relationship between the severity of pain/CSS and clinical progresses remains unclear. This multicenter, collaborative, longitudinal study aimed to characterize the clinical outcomes of patients with musculoskeletal pain by classifying subgroups based on the severity of pain/CSS and examining changes in subgroups over time. We measured the pain intensity, CSS, catastrophic thinking, and body perception disturbance in 435 patients with musculoskeletal pain. Reevaluation of patients after one month included 166 patients for pain intensity outcome and 110 for both pain intensity and CSS outcome analysis. We classified the patients into four groups (mild pain/CSS, severe pain/mild CSS, severe pain/CSS, and mild pain/severe CSS groups) and performed multiple comparison analyses to reveal the differences between the CSS severity groups. Additionally, we performed the adjusted residual chi-square to identify the number of patients with pain improvement, group transition, changing pain, and CSS pattern groups at baseline. The most characteristic result was that the mild and severe CSS groups showed worsening pain. Moreover, many of the group transitions were to the same group, with a few transitioning to a group with mild pain/CSS. Our findings suggest that the severity and improvement of CSS influence pain prognosis.

Altered pain processing and sensitization in sickle cell disease: a scoping review of quantitative sensory testing findings

OBJECTIVES

Over 50% of adults living with sickle cell disease (SCD) have chronic pain, but the underlying mechanisms of chronic pain in this population remain unclear. Quantitative sensory testing is an important measurement tool for understanding pain and sensory processing. This scoping review summarizes quantitative sensory testing methodologies used in sickle cell studies and the evidence for central sensitization in this population.

METHODS

We conducted a systematic search of PubMed, Embase, and CINAHL to identify studies using quantitative sensory testing in individuals living with sickle cell disease. Search strategies were based on variations of the terms "sickle cell disease," and "quantitative sensory testing." Eligible studies were observational or experimental studies in human participants living with SCD that reported findings and detailed methodology for at least 1 quantitative sensory testing modality.

RESULTS

Our search yielded a total of 274 records; 27 of which are included in this scoping review. Of the 27 studies, 17 were original studies (with combined total of 516 adult and 298 pediatric participants), and 10 were secondary or subgroup analyses of these prior studies. Significant variation existed in quantitative sensory testing methodologies across studies, including testing locations, type and intensity of stimuli, and interpretation of findings. Of the identified studies, 22% (2/9 studies) reported sensory abnormalities in mechanical sensitivity and thresholds, 22% (2/9 studies) reported abnormal pressure pain thresholds, 46% (6/13 studies) reported sensory abnormalities in thermal pain thresholds and tolerance (cold and warm), and 50% (2/4 studies) reported abnormalities in temporal summation.

CONCLUSION

Future studies should use standardized quantitative sensory testing protocols with consistent and operationalized definitions of sensitization to provide clear insight about pain processing and central sensitization in sickle cell disease.

Central Sensitization in Psoriatic Arthritis: Relationship With Composite Measures of Disease Activity, Functional Disability, and Health-Related Quality of Life

OBJECTIVE

To investigate the prevalence of central sensitization (CS) in patients with psoriatic arthritis (PsA) and its association with disease activity and patient-reported outcome measures.

METHODS

This cross-sectional study included adults with PsA without coexisting fibromyalgia (FM). Patients underwent a clinimetric assessment to collect variables regarding disease activity, quality of life (QOL), functional ability, impact of disease, and CS. Spearman ρ was used to examine the relationship between CS Inventory (CSI) scores and other variables. A multivariate analysis was performed to determine the independent contribution of each variable to the 12-item Psoriatic Arthritis Impact of Disease (PsAID-12) score.

RESULTS

One hundred fifty-seven patients were enrolled. Of them, 45.2% scored a CSI ≥ 40, indicating a high probability of CS. Significant correlations were found between CSI and disease activity, as evaluated by Disease Activity in Psoriatic Arthritis score and Psoriatic Arthritis Disease Activity Score (ρ 0.587 and ρ 0.573, respectively), between CSI and the Health Assessment Questionnaire (ρ 0.607), and between CSI and the 36-item Short Form Health Survey physical component summary and mental component summary scores (ρ -0.405 and ρ -0.483, respectively). In multivariate analysis, CSI score was the principal independent variable (P < 0.001) contributing to PsAID-12 score.

CONCLUSION

Patients with PsA with symptoms of CS had higher disease activity, worse functional ability, and worse QOL. The presence of CS is the major contributor in the impact of disease.

Frequency of idiopathic intracranial hypertension with ultrasound in patients with fibromyalgia: Relation with function, central sensitization, and neuropathic pain

OBJECTIVE

The purpose of this study was to evaluate the prevalence of idiopathic intracranial hypertension (IIH) in fibromyalgia (FMS) patients by utilizing ultrasound to measure the optic nerve sheath diameter (ONSD), a marker of elevated intracranial pressure and also to investigate the relationship with function, fatigue, quality of life (QOL), central sensitization (CS) and neuropathic pain.

METHODS

The study encompassed 80 female FMS patients and 75 healthy controls. Ultrasound was employed to measure the average ONSD in both groups. Conditions potentially elevating intracranial pressure were ruled out following neurological assessments. Pain (via visual analog scale, VAS), function (revised Fibromyalgia Impact Questionnaire, r-FIQ), QOL (Short Form-36, SF-36), fatigue (fatigue severity scale, FACIT), CS (Central Sensitization Scale), and neuropathic pain (Douleur Neuropathique-4) were evaluated.

RESULTS

The average ONSD was significantly higher in the patient group than the control group. Patients with ONSD >5.5 mm consistent with IIH were categorized as Group 1 (n = 54, 67.5%), while those with a diameter of 5.5 mm and below-formed Group 2. VAS pain (p = .033) and FIQ-R scores (p = .033) were significantly higher in Group 1 than Group 2. Headache was found more common in Group 1.

CONCLUSION

This study unveils a substantial occurrence (67.5%) of IIH in FMS patients, suggesting shared pathophysiological mechanisms contributing to symptoms like fatigue, headache, and cognitive dysfunction. Additionally, these findings implicate heightened functional impairment, CS, headache, and fatigue in FMS patients with IIH.

Based on spinal central sensitization creating analgesic screening approach to excavate anti-neuropathic pain ingredients of Corydalis yanhusuo W.T.Wang

ETHNOPHARMACOLOGICAL RELEVANCE

Corydalis Rhizome (RC) as a traditional analgesic Chinese medicine is the dried tuber of Corydalis yanhusuo W.T.Wang. Many efforts have revealed that RC could effectively alleviate neuropathic pain, while its active ingredients in neuropathic pain are still not clear.

AIM OF THE STUDY

Spinal central sensitization contributes greatly to neuropathic pain, and neuron, astrocyte and microglia play important roles in spinal central sensitization. The aim of the present study is to excavate active compounds in RC regulating spinal central sensitization to inhibit neuropathic pain.

MATERIALS AND METHODS

Immunofluorescence and western blotting were used to determine protein expression levels. Gene expression levels were detected by RT-PCR. PC12 neuronal cells, C6 astrocyte cells, and BV2 microglia cells were cultured for in vitro studies. Targeting multi types of cells extraction combined with HPLC-Q-TOF-MS/MS was established to identify components binding to above cells. Animal studies were used to verify the analgesic activities of components.

RESULTS

Total alkaloids of RC (RC-TA) significantly relieved neuropathic pain in chronic constriction injury (CCI) rats and repressed spinal central sensitization. Eight components of RC-TA were found to bind to PC12, C6, or BV2 cells. They could respectively suppress the activation of cells in vitro and alleviate CCI-induced neuropathic pain, among which glaucine and dehydrocorydaline induced antinociception was stronger than l-THP. Meanwhile, glaucine had no effect on acute or chronic inflammatory pain, and its antinociception in neuropathic pain could be abolished by dopamine D1 receptor agonist.

CONCLUSIONS

Employing multi types of cells based on spinal central sensitization rather than single cell may allow for more thorough excavation of active substances. Glaucine was firstly found could attenuate neuropathic pain but not other types of pain which indicated that different alkaloids in RC exert distinct analgesic effects on different pain models, and gluacine has the potential to be developed as an analgesic drug specifically for neuropathic pain relieving.

Central Sensitization and Neuropathic Pain Cumulatively Affect Patients Reporting Inferior Outcomes Following Total Knee Arthroplasty

UPDATE

This article was updated on November 17, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 102, the text that had read "In a post hoc analysis of the preoperative results, Group 1 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). Groups 2 and 3 showed worse preoperative WOMAC pain, function, and total subscores compared with Group 4 (p < 0.05 for all). These results remained the same at 2 years after surgery." now reads "In a post hoc analysis of the preoperative results, Groups 1, 2, and 3 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). At 2 years postoperatively, Group 1 showed inferior WOMAC pain, function, and total scores compared with the other groups (p < 0.05 for all). Also, Groups 2 and 3 had worse WOMAC pain, function and total scores compared with Group 4 (p < 0.05 for all)." Also, on page 106, the title of Table IV, which had previously read "Inter-Group Comparison of Preoperative Scores (Post Hoc Analysis)" now reads "Inter-Group Comparison of Postoperative Scores (Post Hoc Analysis)."

The Role of the Brain-Derived Neurotrophic Factor in Chronic Pain: Links to Central Sensitization and Neuroinflammation

Chronic pain is sustained, in part, through the intricate process of central sensitization (CS), marked by maladaptive neuroplasticity and neuronal hyperexcitability within central pain pathways. Accumulating evidence suggests that CS is also driven by neuroinflammation in the peripheral and central nervous system. In any chronic disease, the search for perpetuating factors is crucial in identifying therapeutic targets and developing primary preventive strategies. The brain-derived neurotrophic factor (BDNF) emerges as a critical regulator of synaptic plasticity, serving as both a neurotransmitter and neuromodulator. Mounting evidence supports BDNF's pro-nociceptive role, spanning from its pain-sensitizing capacity across multiple levels of nociceptive pathways to its intricate involvement in CS and neuroinflammation. Moreover, consistently elevated BDNF levels are observed in various chronic pain disorders. To comprehensively understand the profound impact of BDNF in chronic pain, we delve into its key characteristics, focusing on its role in underlying molecular mechanisms contributing to chronic pain. Additionally, we also explore the potential utility of BDNF as an objective biomarker for chronic pain. This discussion encompasses emerging therapeutic approaches aimed at modulating BDNF expression, offering insights into addressing the intricate complexities of chronic pain.

Central Sensitisation Syndrome: A Frequent Finding in Women with Pelvic Floor Symptoms Without Evident Urogenital Prolapse

INTRODUCTION AND HYPOTHESIS

Women with central sensitisation syndrome (CSS) experience poorer subjective post-operative outcomes even after successful pelvic floor reconstruction. This study tests the hypothesis that women with pelvic floor symptoms (PFS) without relevant pelvic organ prolapse (POP), are more likely to have CSS.

METHODS

A questionnaire was sent to women who participated in the POP-UP study in 2017. The POP-UP study evaluated POP in 247 women 16 years after laparoscopic or vaginal hysterectomy. POP-Q data and Pelvic Floor Distress Inventory (PFDI-20) results were used and supplemented with CSS-specific questionnaires. A Central Sensitisation Inventory (CSI) score above 40 implicates CSS. Women were divided into groups based on POP beyond the hymen in relation to the PFDI-20 score. Outcomes of women with PFS and without POP (called 'group 1') were compared with the rest of the cohort (groups 2-4; women without PFS and/or with POP).

RESULTS

A total of 136 women were included in the analysis. A CSI score above 40 was present in 16 out of 42 women of group 1 (37%) versus 11 out of 93 women of groups 2-4 (12%), p < 0.0001. Passive coping was more prevalent in group 1 (p = 0.039), and more deviations in somatisation, depression, anxiety and distress were found in group 1 (p values of < 0.0001, 0.018, 0.003 and 0.002 respectively).

CONCLUSIONS

This study suggests that CSS might be more prevalent in women with PFS without relevant POP. More awareness of CSS and valid individual counselling may overcome unnecessary surgery for POP and help in setting realistic expectations.

Effects of sleep quality on pain, cognitive factors, central sensitization, and quality of life in patients with chronic low back pain

BACKGROUND

Sleep quality in patients with chronic low back pain (CLBP) may affect quality of life (QoL), possibly due to worsening pain, central sensitization (CS), and cognitive factors. However, causal relationship among the factors has not been confirmed yet.

OBJECTIVE

The purpose of this study was to test the hypothesis that sleep quality in patients with CLBP is attributable to pain, cognitive factors, and CS, and influences QoL, by structural covariance analysis.

METHODS

This is a cross-sectional study. Participants were recruited from six health care facilities and 101 patients with CLBP were included. Structural covariance analysis assessed the fit of data to the model using goodness of fit index (GFI), adjusted goodness of fit index (AGFI), comparative fit index (CFI), and mean squared approximation error (RMSEA).

RESULTS

The structural covariance analysis showed that the goodness-of-fit indices were high (GFI = 0.993, AGFI = 0.964, CFI = 1.00, RMSEA < 0.01). Sleep quality was not directly influenced by QoL but rather by CS and cognitive factors.

CONCLUSION

This study suggests that sleep quality in patients with CLBP is indirectly mediated through multiple pathways, including cognitive factors and CS, which may influence QoL.

Central sensitization adversely affects quality of recovery following lumbar decompression surgery

BACKGROUND

Central sensitization (CS) is defined as increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold afferent input. The CS phenomenon is caused by continuous, intense nociceptor inputs triggering a prolonged but reversible increase in the excitability and synaptic efficacy of neurons in the central nociceptive pathway. Most patients undergoing surgery for lumbar spinal stenosis (LSS) experience symptoms for more than three months; therefore, it is possible that CS is associated with postoperative symptoms of LSS. The aim of this study was to clarify the influence of CS in patients who underwent surgery for LSS.

METHODS

We used the Central Sensitization Inventory (CSI) to evaluate CS preoperatively. Clinical and neurological symptoms were assessed before surgery and three months after surgery using the Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOA-BPEQ) and the Oswestry Disability Index (ODI). To evaluate the correlation between the preoperative CSI score and each parameter of the JOA-BPEQ before and three months after surgery, a Pearson correlation coefficient was used. We also evaluated the correlation between preoperative CSI and improvement scores for each parameter of the JOA-BPEQ for surgery. Similarly, the ODI was assessed.

RESULTS

This study included 118 patients. After surgery, the parameters of lumbar function disorder, social life function disorder, and mental health disorder revealed a statistically significant relationship (r = -0.289, -0.0354, and -0.493, respectively). There was no significant correlation between CSI and improvement scores of the JOA-BPEQ. The ODI assessment after surgery revealed a statistically significant relationship (r = 0.344). There was no significant correlation between the CSI and ODI improvement scores.

CONCLUSION

This study showed that the severity of the CSI influenced the postoperative outcomes, and that surgical treatment improved the symptoms of LSS regardless of the occurrence of CS preoperatively.

Influence of radiological factors, psychosocial factors, and central sensitization-related symptoms on clinical symptoms in patients with lumbar spinal canal stenosis

BACKGROUND

No study to date has concurrently evaluated the impact of radiological factors, psychosocial factors, and central sensitization (CS) related symptoms in a single lumbar spinal canal stenosis (LSS) patient cohort.

OBJECTIVE

To investigate the associations between these factors and clinical symptoms in LSS patients.

METHODS

We recruited 154 patients with LSS scheduled for surgery. Patient-reported outcome measures and imaging evaluation including clinical symptoms, psychosocial factors, CS-related symptoms, and radiological classifications. Spearman's rank correlation coefficient and multiple regression analyses were employed.

RESULTS

Spearman's correlation revealed CS-related symptoms positively correlated with low back pain (r= 0.25, p< 0.01), leg pain (r= 0.26, p< 0.01), and disability (r= 0.32, p< 0.01). Pain catastrophizing positively correlated with leg pain (r= 0.23, p< 0.01) and disability (r= 0.36, p< 0.01). Regression analysis showed that pain catastrophizing was associated with disability (β= 0.24, 95%CI = 0.03-0.18), and CS-related symptoms with low back pain (β= 0.28, 95%CI = 0.01-0.09). Radiological classifications were not associated with clinical symptoms.

CONCLUSION

Our findings suggest that psychosocial factors and CS-related symptoms, rather than radiological factors, seem to contribute to clinical symptoms in patients with LSS.

The role of pain modulation pathway and related brain regions in pain

Pain is a multifaceted process that encompasses unpleasant sensory and emotional experiences. The essence of the pain process is aversion, or perceived negative emotion. Central sensitization plays a significant role in initiating and perpetuating of chronic pain. Melzack proposed the concept of the "pain matrix", in which brain regions associated with pain form an interconnected network, rather than being controlled by a singular brain region. This review aims to investigate distinct brain regions involved in pain and their interconnections. In addition, it also sheds light on the reciprocal connectivity between the ascending and descending pathways that participate in pain modulation. We review the involvement of various brain areas during pain and focus on understanding the connections among them, which can contribute to a better understanding of pain mechanisms and provide opportunities for further research on therapies for improved pain management.

Cross-cultural adaptation and validation for central sensitization inventory: based on Chinese patients undergoing total knee arthroplasty for knee osteoarthritis

BACKGROUND

This study was conducted to develop a simplified Chinese version of the central sensitization inventory (CSI-CV) and to evaluate its reliability and validity.

METHODS

The CSI-CV was developed through a process involving the translation and back translation of the original CSI. Subsequently, experts reviewed and revised the content of the items to ensure their appropriateness. A total of 325 patients with knee osteoarthritis (KOA), who were scheduled to undergo total knee arthroplasty (TKA), completed the CSI-CV at a prominent orthopedic center in Xi'an, China. Afterward, a random selection of 100 participants was chosen for retesting after one week. The reliability and validity of the inventory were evaluated through exploratory factor analysis, correlation coefficient calculation and other methods.

RESULTS

The CSI-CV consists of 25 items in five dimensions (emotional distress, headache and jaw symptoms, physical symptoms, urological symptoms, and fatigue and sleep problems). The cumulative variance contribution rate was 75.3%, the Cronbach's α coefficient was 0.83, the Guttman split-half reliability coefficient was 0.88 and the intraclass correlation coefficient was 0.965. The CSI-CV scores correlated moderately with the total scores of the brief pain inventory (r = 0.506), Western Ontario and McMaster Universities Osteoarthritis Index (r = 0.466) and EuroQoL Group's five-dimension questionnaire (r = 0.576).

CONCLUSIONS

The findings demonstrate that the CSI was successfully trans-culturally adapted into a simplified Chinese version (CSI-CV) that was reliable and valid for Chinese-speaking patients who awaiting TKA for KOA.

Central sensitization negatively influences the level of disability in female patients with anterior knee pain

PURPOSE

To define the prevalence of Central Sensitization (CS) in patients with Anterior Knee Pain (AKP) and determine whether there is an association between CS and the magnitude of pain, disability, quality-of-life and psychological impairment.

METHODS

The data of a total of 44 AKP female patients with a mean age of 27.7 years (15-50) recruited consecutively from hospital outpatient knee clinics were prospectively included in this study. The patients had no antecedents of knee trauma or surgery and no history of injury or disease of the nervous system. There were also 50 healthy female controls with a mean age of 26.1 years (16-46). CS was evaluated using the Central Sensitization Inventory (CSI). Quality-of-life was evaluated using the EuroQoL-5D questionnaire. Self-reporting of clinical pain intensity was obtained using the Visual Analogue Scale. The Kujala Knee Scale and IKDC form were used to evaluate disability. Anxiety and depression were evaluated using the Hospital Anxiety and Depression Subscale (HAD). Kinesiophobia was measured with the Tampa Scale for Kinesiophobia (TSK-11) and catastrophizing by means of the Pain Catastrophizing Scale (PCS).

RESULTS

Sixteen AKP patients (36%), and 2 (4%) of the healthy controls presented with central sensitization (p < 0.01). AKP patients with CS have a greater degree of disability based on the Kujala Scale and higher levels of anxiety and depression than AKP patients without CS. The score of AKP patients in the CSI correlated weakly with disability and quality of life and moderately with anxiety and depression. However, no association was seen between CSI score and pain intensity, nor with catastrophizing and kinesiophobia. A multivariate logistic regression analysis showed that only depression was statistically significant in the prediction of the presence of CS (odds ratio 1.45; 95% CI 1.07 to 1.96).

CONCLUSIONS

AKP patients have a significantly higher prevalence of CS in comparison with what has been reported for the general population. This finding suggests the presence of altered pain modulation in a subgroup of AKP patients.

LEVEL OF EVIDENCE

Level III.

Low central sensitisation inventory score is associated with better post-operative outcomes of osteotomy around the knee

PURPOSE

The purpose of this study was to investigate the potential association between central sensitisation inventory (CSI) scores and post-operative patient-reported outcomes (PROs) in patients underwent osteotomy around the knee (OAK), with a CSI cut-off score specific for knee osteoarthritis.

METHODS

CSI scores were collected from 173 patients who underwent OAK, along with their knee injury and osteoarthritis outcome score (KOOS) and pain numeric rating scale (NRS) scores. Patients were divided into high-CSI score group and low-CSI score group with a cut-off score of 17. Multivariate linear regression was performed to test the association between CSI scores and post-operative outcomes. Pre-surgery KOOS and NRS scores and the rate of attainment of minimal clinically important difference (MCID) of KOOS scores was analysed as secondary outcomes.

RESULTS

Low-CSI score group had significantly higher post-operative KOOS scores and lower pain NRS scores compared to the high-CSI score group (< p = 0.01) after adjusting for confounding factors. For pre-operative scores, only the KOOS-Symptom score was significantly different between the groups (64.7 ± 20.1 when CSI < 17 vs.55.1 ± 19.7 when CSI ≥ 17; p = 0.008). The low-CSI score group had significantly higher MCID achievement rates of KOOS-Pain, Symptom, and ADL than the high-CSI score group (86% vs. 68%; 74% vs. 55%; 86% vs. 67%, respectively; P < 0.05).

CONCLUSIONS

This study established an association between post-operative CSI scores ≥ 17 and poorer outcomes following OAK, highlighting the potential value of the CSI in identifying patients in need of more comprehensive peri-operative pain management.

LEVEL OF EVIDENCE

Level III. Retrospective comparative study.

Central Sensitization in Vulvodynia and Endometriosis: What Have We Been Overlooking So Far?

Importance

Women experience more frequent and greater pain than men, although they receive less adequate treatment and are perceived as more anxious than males. Recent clinical research has lead to hypothesize a common etiology for overlapping chronic pain conditions and mood disorders, namely, central sensitization, which originates from an alteration of pain processing pathways in the central nervous system.

Objective

The aim of this review was to collect all available evidence regarding the potential role of central sensitization in vulvodynia and endometriosis.

Evidence Acquisition

A systematic literature search was performed between July and August 2022 using the electronic database PubMed. The extracted data were summarized using a narrative approach.

Results

Ten articles were chosen for the review. Participants' mean age was 39.2 years (SD = 5.1). Among serum markers of central sensitization, nitric oxide levels were greater in women with endometriosis than in controls, whereas brain-derived neurotrophic factor and S100B levels differed among pain conditions with structural anomalies and those without. Functional magnetic resonance imaging showed different resting state networks between patients with endometriosis and controls. In neurophysiology studies, cases had reduced pain thresholds, compared with healthy controls. Lastly, self-reported questionnaires suggested a central component of pain in women with endometriosis-related dyspareunia and associated bladder/pelvic floor tenderness.

Conclusions and Relevance

The management of vulvodynia and endometriosis may benefit from a new perspective, which considers their possible central etiology. It is compelling that treatment of pain starts to be considered a therapeutic goal in its own right.

Ac4C Enhances the Translation Efficiency of Vegfa mRNA and Mediates Central Sensitization in Spinal Dorsal Horn in Neuropathic Pain

N4-Acetylcytidine (ac4C), a highly conserved post-transcriptional machinery with extensive existence for RNA modification, plays versatile roles in various cellular processes and functions. However, the molecular mechanism by which ac4C modification mediates neuropathic pain remains elusive. Here, it is found that the enhanced ac4C modification promotes the recruitment of polysome in Vegfa mRNA and strengthens the translation efficiency following SNI. Nerve injury increases the expression of NAT10 and the interaction between NAT10 and Vegfa mRNA in the dorsal horn neurons, and the gain and loss of NAT10 function further confirm that NAT10 is involved in the ac4C modification in Vegfa mRNA and pain behavior. Moreover, the ac4C-mediated VEGFA upregulation contributes to the central sensitivity and neuropathic pain induced by SNI or AAV-hSyn-NAT10. Finally, SNI promotes the binding of HNRNPK in Vegfa mRNA and subsequently recruits the NAT10. The enhanced interaction between HNRNPK and NAT10 contributes to the ac4C modification of Vegfa mRNA and neuropathic pain. These findings suggest that the enhanced interaction between HNRNPK and Vegfa mRNA upregulates the ac4C level by recruiting NAT10 and contributes to the central sensitivity and neuropathic pain following SNI. Blocking this cascade may be a novel therapeutic approach in patients with neuropathic pain.

Central sensitization as a predictive factor for the surgical outcome in patients with lumbar spinal stenosis: a multicenter prospective study

PURPOSE

The impact of central sensitization (CS) on neurological symptoms and surgical outcomes in patients with lumbar spinal stenosis (LSS) remains unknown. This study aimed to investigate the influence of preoperative CS on the surgical outcomes of patients with LSS.

METHODS

A total of 197 consecutive patients with LSS (mean age 69.3) who underwent posterior decompression surgery with or without fusion were included in this study. The participants completed the CS inventory (CSI) scores and the following clinical outcome assessments (COAs) preoperatively and 12 months postoperatively: the Japanese Orthopaedic Association (JOA) score for back pain, JOA back pain evaluation questionnaire, and Oswestry Disability Index (ODI). The association between preoperative CSI scores and preoperative and postoperative COAs was analyzed, and postoperative changes were statistically evaluated.

RESULTS

The preoperative CSI score significantly decreased at 12 months postoperatively and was significantly correlated with all COAs preoperatively and 12 months postoperatively. Higher preoperative CSI showed worse postoperative COAs and inferior postoperative improvement rates in the JOA score, VAS score for neurological symptoms, and ODI. Multiple regression analysis demonstrated that preoperative CSI was significantly associated with postoperative low back pain (LBP), mental health, quality of life (QOL), and neurological symptoms at 12 months postoperatively.

CONCLUSIONS

Preoperative CS evaluated by CSI had a significantly worse impact on surgical outcomes, including neurological symptoms, disability, and QOL, especially related to LBP and psychological factors. CSI can be used clinically as a patient-reported measure for predicting postoperative outcomes in patients with LSS.

Central Sensitisation Inventory-Thai version: translation, cross-cultural adaptation, and psychometric evaluation in chronic non-specific neck pain

PURPOSE

To translate and cross-culturally adapt the English version of the Central Sensitisation Inventory (CSI) into Thai (CSI-Thai) and to evaluate its psychometric properties in individuals with chronic non-specific neck pain.

MATERIALS AND METHODS

Cross-cultural translation and adaptation of the CSI were performed according to standard guidelines. A total of 340 participants were invited to complete the CSI-Thai, Visual Analogue Scale (pain intensity), Neck Disability Index, Fear-Avoidance Beliefs Questionnaire, Pain Catastrophising Scale (PCS), and Short Form-36. Psychometric evaluation included confirmatory factor analysis, internal consistency, test-retest reliability, agreement, and construct validity.

RESULTS

Dimensionality analyses indicated that a bifactor model, comprising one general factor plus four orthogonal factors, fit the CSI structure better than unidimensional and the four-factor models. The general factor showed substantial reliability (Cronbach α = 0.91, Omega ω = 0.94, and omega hierarchical ω-h = 0.91). The intraclass correlation coefficient was 0.90, representing excellent stability over a 48 h interval. Moderate-to-strong correlations and acceptable-to-excellent discriminations were found between the CSI-Thai and all questionnaires. The exception was the PCS (no correlation and discrimination). The standard error of measurement and minimal detectable change of the CSI-Thai were 2.33 and 6.47, respectively.

CONCLUSIONS

The translation and cross-cultural adaptation of the CSI-Thai were successful, with satisfactory reliability and construct validity.Implications for rehabilitationCentral Sensitisation Inventory-Thai version (CSI-Thai) is successfully adapted and demonstrated satisfactory reliability and construct validity.The CSI-Thai can be applicable to assess central sensitisation-related signs and symptoms in Thai-speaking patients with chronic non-specific neck pain (CNSNP) both clinical and research purposes.The CSI-Thai correlated to pain, disability and quality of life among patients with CNSNP.

The crosstalk of the pathophysiologic models in fibromyalgia

Fibromyalgia (FM) is a heterogeneous condition with various mechanisms (endotype) and manifestations (phenotypes). Many worthy endeavors have been dedicated to exploring the main trajectories of FM pathogenesis, depicted as the models of FM development. The Imbalance of Threat and Soothing Systems (FITSS) model, which is an advancing psychosocial form of the "central sensitization" model, and autonomic nervous system (ANS) model, besides new discoveries of potential pathways for FM development such as autoimmunity, small fiber pathology, and gut-brain axis currently comprise all our knowledge assets about FM pathogenesis. The pathophysiology of fibromyalgia is too complex to justify with one model, one main loop of pathogenesis, and one terminator. It appears that the variable FM models could justify some phenotypes of FM. Currently, our knowledge about FM pathogenesis and trying to match the different pathways and links mimic solving a puzzle in the hands of beginners. Until unraveling many missed interconnections and formulas between numerous scrambled pieces of the FM puzzle, proposing an integrated model seems not possible. This review focuses on the main trajectories of FM pathogenesis proposed thus far and tries to illuminate the crosstalking between them. We also propose the subgrouping FM into more homogenous categories based on the endotype-phenotype characteristics. It could provide a more pragmatic approach toward understanding of the diverse network of FM pathogenesis as well as the personalized stratification of FM. Key Points • The disentangled nature of FM pathogenesis escapes from embracing under one integrated model. • There appears to be no way for formulizing FM pathogenesis except the acknowledgment of the different pathways and their crosstalk explored as yet. • Acknowledging the different endotypes/phenotypes of FM spectrum and classifying them into more homogenous groups can help to the pragmatic approach to FM.

Association of central sensitization, visceral fat, and surgical outcomes in lumbar spinal stenosis

BACKGROUND

Controversy remains regarding predictors of surgical outcomes for patients with lumbar spinal stenosis (LSS). Pain sensitization may be an underlying mechanism contributing to LSS surgical outcomes. Further, obesity is associated with dissatisfaction and poorer outcomes after surgery for LSS. Therefore, this study aimed to examine the relationship between central sensitization (CS), visceral fat, and surgical outcomes in LSS.

METHODS

Patients with LSS were categorized based on their central sensitization inventory (CSI) scores into low- (CSI < 40) and high- (CSI ≥ 40) CSI subgroups. The participants completed clinical outcome assessments preoperatively and 12 months postoperatively.

RESULTS

Overall, 60 patients were enrolled in the study (28 men, 32 women; mean age: 62.1 ± 2.8 years). The high-CSI group had significantly higher mean low back pain (LBP), leg pain, and leg numbness visual analogue scale (VAS) scores than the low-CSI group (p < 0.01). The high-CSI group had a significantly higher mean visceral fat area than the low-CSI group (p < 0.01). Postoperatively, LBP VAS score was significantly worse in the high-CSI group. Relative to preoperatively, postoperative leg pain and leg numbness improved significantly in both groups.

CONCLUSIONS

We believe that neuro decompression can be effective for LSS surgical outcomes in patients with CS; nonetheless, it should be approached with caution owing to the potential for worsening LBP. Additionally, visceral fat is an important indicator suggesting the involvement of CS.

Impact of central sensitization on pain, disability and psychological distress in patients with knee osteoarthritis and chronic low back pain

BACKGROUND

Central sensitization (CS) is becoming increasingly recognized as a significant factor in many chronic pain conditions, including knee osteoarthritis (KOA) and chronic low back pain (CLBP). Yet it presently remains unclear how strong is the involvement of CS in KOA and CLBP and which factors are involved in CS in these two chronic disabling diseases.

METHODS

This is a cross-sectional study in which included a total of 178 patients with KOA and 118 patients with CLBP. Inclusion criteria for eligible participants for the KOA group were a confirmed diagnosis of KOA according to the American College of Rheumatology criteria, and for the CLBP group a chronic low back pain for more than 3 months. Subjects were excluded if they presented with a diagnosed psychiatric disorder or if they lacked the capacity to provide informed consent, understand study questionnaires or perform physical performance tests. In each group, were assessed; CS-related symptoms using the Central Sentization Inventory (CSI); demographic and clinical characteristics such as disease duration, pain intensity on a visual analog scale, self-reported function using the Lequesne index for KOA patients and the Oswestry Disability index for CLBP patients, and physical performance with the 6 minutes' walk test; as well as psychosocial risk factors using the Patient Health Questionnaire for depression (PHQ-9), the Generalized Anxiety Disorder (GAD-7) and the Pain Catastrophizing Scale (PCS).

RESULTS

CSI scores significantly correlated with pain intensity and disability in KOA and CLBP patients, and were highly correlated with self-reported symptoms of depression, anxiety and pain catastrophizing. Depression significantly predicted the CSI score in both groups.

CONCLUSION

These findings provide further evidence for the impact of CS on pain, function and physical performance in KOA and CLBP patients. Psychosocial symptoms such as pain catastrophizing, anxiety and depression should also be considered as they are also associated with CS.

Insomnia is associated with symptoms of central sensitization in patients with painful temporomandibular disorders

BACKGROUND

Central sensitization (CS) and temporomandibular disorder (TMD) are both associated with insomnia. Therefore, the authors aimed to investigate whether insomnia was associated with more symptoms of CS in patients with TMD.

METHODS

In 82 volunteers with TMD, insomnia was clinically assessed, allowing sample stratification according to its presence. The Central Sensitization Inventory questionnaire was self-applied to assess the clinical symptoms of CS.

RESULTS

Participants with insomnia had significantly higher mean (SD) scores of CS according to the Central Sensitization Inventory than participants without insomnia (43.10 [12.57] vs 26.59 [13.66]; P = < .001).

CONCLUSIONS

Insomnia was associated with higher scores of CS symptoms in patients with TMD.

PRACTICAL IMPLICATIONS

Insomnia influences TMD as well as its relationship with CS, and, therefore, it is critical to the clinical management of TMD.

Evaluation of a scoring system for the detection of central sensitization among women with chronic pelvic pain

BACKGROUND

Central sensitization is frequently associated with chronic pelvic pain and requires specific management. The pain is described as hypersensitivity to an innocuous stimulus that is both widespread and persistent. However, no study has evaluated if central sensitization can be measured objectively with neurophysiological tests in the pelvic and perineal area to prove this concept in women with chronic pelvic pain.

OBJECTIVE

This study aimed to evaluate nociceptive thresholds (primary objective) and spatial and temporal diffusion of pain among women with chronic pelvic pain and high or low scores of central sensitization.

STUDY DESIGN

This prospective, assessor-blinded, comparative study compared a cohort of women with chronic pelvic pain and a high (>5/10; n=29) vs low (<5/10; n=24) score of sensitization according to the Convergences PP criteria. Participants underwent a noninvasive bladder sensory test, a rectal barostat test, and a muscular (algometer) and a vulvar (vulvagesiometer) sensory test. Poststimulation pain (minutes), quality of life (Medical Outcomes Study 36-Item Short Form Survey), and psychological state, comprising anxiety (State-Trait Anxiety Inventory), depression (Beck Depression Inventory Short Form), and catastrophizing (Pain Catastrophizing Scale), were assessed.

RESULTS

The participants mostly suffered from endometriosis (35.8%), irritable bowel syndrome (35.8%), bladder pain syndrome (32.1%), and vestibulodynia (28.3%). Baseline characteristics were similar. Women with a high sensitization score had more painful diseases diagnosed (2.7±1.3 vs 1.6±0.8; P=.002) and suffered for longer (11±8 vs 6±5 years; P=.028) than participants with a low score. The bladder maximum capacity was equivalent between participants (399±168 vs 465±164 mL; P=.18). However, the pain felt at each cystometric threshold was significantly increased in women with a high sensitization score. No difference was identified for the rectal pain pressure step (29.3±5.5 vs 30.7±6.5 mm Hg; P=.38). Rectal compliance was decreased in women with a high sensitization score with a considerable increase in pain felt. The average of pain pressure thresholds at the 5 vulvar sites tested was decreased in these participants (162.5±90.5 vs 358.7±196.5 g; P=.0003). Similar results were found for the average of the pain pressure thresholds at 6 muscles tested (1.34±0.41 vs 2.63±1.52 kg/m2; P=.0002). A longer period was needed for patients with high sensitization score to obtain a VAS <3 out of 10 after the stimulation of the bladder (4.52±5.26 vs 1.27±2.96 minutes; P=.01), the rectum (3.75±3.81 vs 1.19±1.23 minutes; P=.009), and the muscles (1.46±1.69 vs 0.64±0.40 minutes; P=.002). The psychological state was equivalent between groups. No association was found between the sensory thresholds and the psychological state results. The physical component of the quality of life score was reduced in women with high sensitization score (P=.0005), with no difference in the mental component.

CONCLUSION

Using neurophysiological tests, this study showed that there are objective elements to assess for the presence of central sensitization, independently of psychological factors.

Cluster Analysis of Subjective Shoulder Stiffness and Muscle Hardness: Associations with Central Sensitization-Related Symptoms

Background and Objectives: Understanding the relationships between subjective shoulder stiffness, muscle hardness, and various factors is crucial. Our cross-sectional study identified subgroups of shoulder stiffness based on symptoms and muscle hardness and investigated associated factors. Materials and Methods: measures included subjective stiffness, pain, muscle hardness, and factors like physical and psychological conditions, pressure pain threshold, postural alignment, heart rate variability, and electroencephalography in 40 healthy young individuals. Results: Three clusters were identified: Cluster 1 with high stiffness, pain, and muscle hardness; Cluster 2 with low stiffness and pain but high muscle hardness; and Cluster 3 with low levels of all factors. Cluster 1 had significantly higher central sensitization-related symptoms (CSS) scores than Cluster 2. Subjective stiffness is positively correlated with psychological factors. Conclusions: our results suggest that CSS impacts subjective symptom severity among individuals with similar shoulder muscle hardness.

The role of symptoms severity, heart rate, and central sensitization for predicting sleep quality in patients with fibromyalgia

BACKGROUND

Clinical predictors of sleep quality in patients with fibromyalgia syndrome (FMS) are still unknown. By identifying these factors, we could raise new mechanistic hypotheses and guide management approaches. We aimed to describe the sleep quality of FMS patients and to explore the clinical and quantitative sensory testing (QST) predictors of poor sleep quality and its subcomponents.

METHODS

This study is a cross-sectional analysis of an ongoing clinical trial. We performed linear regression models between sleep quality (Pittsburgh Sleep Quality Index [PSQI]) and demographic, clinical, and QST variables, controlling for age and gender. Predictors for the total PSQI score and its seven subcomponents were found using a sequential modeling approach.

RESULTS

We included 65 patients. The PSQI score was 12.78 ± 4.39, with 95.39% classified as poor sleepers. Sleep disturbance, use of sleep medications, and subjective sleep quality were the worst subdomains. We found poor PSQI scores were highly associated with symptom severity (FIQR score and PROMIS fatigue), pain severity, and higher depression levels, explaining up to 31% of the variance. Fatigue and depression scores also predicted the subjective sleep quality and daytime dysfunction subcomponents. Heart rate changes (surrogate of physical conditioning) predicted the sleep disturbance subcomponent. QST variables were not associated with sleep quality or its subcomponents.

CONCLUSIONS

Symptom severity, fatigue, pain, and depression (but no central sensitization) are the main predictors of poor sleep quality. Heart rate changes independently predicted the sleep disturbance subdomain (the most affected one in our sample), suggesting an essential role of physical conditioning in modulating sleep quality in FMS patients. This underscores the need for multidimensional treatments targeting depression and physical activity to improve the sleep quality of FMS patients.

Central sensitization mechanisms in chronic migraine with medication overuse headache: a study of thalamocortical activation and lateral cortical inhibition

BACKGROUND

It is unclear whether cortical hyperexcitability in chronic migraine with medication overuse headache (CM-MOH) is due to increased thalamocortical drive or aberrant cortical inhibitory mechanisms.

METHODS

Somatosensory evoked potentials (SSEP) were performed by electrical stimulation of the median nerve (M), ulnar nerve (U) and simultaneous stimulation of both nerves (MU) in 27 patients with CM-MOH and, for comparison, in 23 healthy volunteers (HVs) of a comparable age distribution. We calculated the degree of cortical lateral inhibition using the formula: 100 - [MU/(M + U) × 100] and the level of thalamocortical activation by analyzing the high frequency oscillations (HFOs) embedded in parietal N20 median SSEPs.

RESULTS

Compared to HV, CM-MOH patients showed higher lateral inhibition (CM-MOH 52.2% ± 15.4 vs. HV 40.4% ± 13.3; p = 0.005), which positively correlated with monthly headache days, and greater amplitude of pre-synaptic HFOs (p = 0.010) but normal post-synaptic HFOs (p = 0.122).

CONCLUSION

Our findings suggest that central neuronal circuits are highly sensitized in CM-MOH patients, at both thalamocortical and cortical levels. The observed changes could be due to the combination of dysfunctional central pain control mechanisms, hypersensitivity and hyperresponsiveness directly linked to the chronic intake of acute migraine drugs.

Negative correlation between central sensitization and forgotten joint score-12 after total hip arthroplasty

BACKGROUND

Central sensitization is a condition in which even mild stimuli cause pain due to increased neuronal reactivity in the dorsal horn of the spinal cord. It is one of factors of chronic pain in patients with osteoarthritis. However, it is unknown whether central sensitization relates to clinical outcomes after total hip arthroplasty (THA). This study aimed to clarify whether preoperative central sensitization relates to the forgotten joint score-12 (FJS) after THA. Moreover, the secondary outcome was to identify which items in the FJS were most related by central sensitization.

METHODS

This retrospective analysis included 263 hips (263 patients; 51 males and 212 females) that underwent primary THA in our institute and were available for evaluation one year postoperatively. The average patient age was 64.8 ± 11.9 years. The Central Sensitization Inventory (CSI) part A, which is a patient-reported outcome, was used to measure preoperative central sensitization. The correlation between preoperative CSI and postoperative FJS and the association between postoperative FJS and preoperative CSI severity were determined. Moreover, difference in each FJS item was evaluated by CSI severity.

RESULTS

Twenty-six patients (9.9%) had central sensitization preoperatively. Preoperative CSI scores and postoperative FJS were negatively correlated (r =  - 0.331, p < 0.0001). The postoperative FJS was significantly lower in patients with moderate or higher preoperative CSI severity than that in patients with subclinical or mild preoperative CSI severity (p < 0.05). FJS items with movement of daily life were significantly worse in the moderate or higher CSI severity compared with subclinical group (p < 0.05 or p < 0.01).

CONCLUSION

Central sensitization prior to THA negatively related to postoperative FJS. In particular, the relationship of central sensitization was found to be significant in FJS items with movement, which would lead to lower patient satisfaction after THA. To get better postoperative outcomes in patients with preoperative central sensitization, improving central sensitization would be important.

HIF-1α/MMP-9 promotes spinal cord central sensitization in rats with bone cancer pain

Bone cancer pain (BCP) is one of the most prevalent and serious symptoms of patients with cancer. Currently, the medical interventions used for the treatment of BCP do not act with optimal safety and efficacy. In this study, we appraised whether the hypoxia-inducible factor 1α (HIF-1α)/metalloproteinase-9 (MMP9) axis activates the PI3K/AKT pathway, resulting in elevated spinal cord central sensitization and aggravated BCP. BCP rats were established by tibial injection of Walker 256 cells, followed by different interventions in rats using HIF-1ɑ inhibitor LW6 or antibody treatments. After treatment with LW6 or antibody against HIF-1α, central sensitization in the spinal cord tissues of rats was inhibited, and pain perception in rats was reduced. Moreover, the activation of glial cells in the spinal cord tissues was ameliorated. The expression of MMP9 was remarkably suppressed in spinal cord tissues after inhibition of HIF-1ɑ activity, and the activity of the PI3K/AKT signaling pathway was inhibited. Further activation of MMP9 expression suppressed the alleviating effect of HIF-1ɑ inhibitor LW6 or antibody on pain perception in rats inoculated with tumors. Taken together, our studies suggest a HIF-1α/MMP9-mediated activation of PI3K/AKT in the spinal cord tissues, resulting in increased pain perception in a rat model with BCP.

Cutaneous allodynia as predictor for treatment response in chronic migraine: a cohort study

BACKGROUND

Central sensitisation is an important mechanism in migraine chronification. It is presumed to occur in second and third order neurons sequentially, resulting in an analogous spatial distribution of cutaneous allodynia with cephalic and extracephalic symptoms. We investigated whether allodynia, and its subtypes based on spatial distribution and type of stimulus, predict response to treatment in chronic migraine patients.

METHODS

This study was conducted as part of the CHARM study (NTR3440), a randomized, double-blind, placebo-controlled trial in chronic migraine patients with medication overuse. We included 173 patients. The presence of cutaneous allodynia at baseline was established with the Allodynia Symptom Checklist. Primary endpoint was reversion from chronic to episodic migraine.

RESULTS

Of all patients, 74.6% reported cutaneous allodynia. Absence of allodynia compared to presence of allodynia was predictive for reversion from chronic to episodic migraine, odds ratio (OR): 2.45 (95% CI: 1.03-5.84), p = 0.042. The predictive value was more pronounced when subdivided for spatial distribution, for participants without allodynia versus cephalic (OR: 4.16 (95% CI: 1.21-14.30), p = 0.024) and extracephalic (OR: 7.32 (95% CI: 1.98- 27.11), p = 0.003) allodynia. Mechanical, but not thermal, allodynia, was associated with outcome.

CONCLUSIONS

Cutaneous allodynia, an important marker for central sensitization, likely has predictive value for treatment response in chronic migraine.

Suffering from chronic tinnitus, chronic neck pain, or both: Does it impact the presence of signs and symptoms of central sensitization?

Chronic subjective tinnitus is a prevalent symptom, which has many similarities with chronic pain. Central sensitization is considered as a possible underlying mechanism of both symptoms. Central sensitization has already been investigated in chronic pain populations but not in patients with chronic subjective tinnitus. Therefore, the main objective of this cross-sectional study was to compare signs and symptoms, indicative for central sensitization, in tinnitus patients with and without chronic idiopathic neck pain, patients with chronic idiopathic neck pain only, and healthy controls. Also, differences in psychological and lifestyle factors, possibly influencing the association between central sensitization and tinnitus, were examined as well as correlations between signs and symptoms of central sensitization, and tinnitus, pain, psychological and lifestyle factors. Differences in signs and symptoms of central sensitization were examined using the self-report Central Sensitization Inventory and QST protocol (local and distant mechanical and heat hyperalgesia, conditioned pain modulation). Tinnitus, pain, psychological and lifestyle factors were evaluated using self-report questionnaires. Symptoms of central sensitization and local mechanical hyperalgesia were significantly more present in both tinnitus groups, compared to healthy controls, but were most extensive in the group with chronic tinnitus+chronic idiopathic neck pain. Distant mechanical hyperalgesia, indicative for central sensitization, was only observed in the group with both chronic tinnitus+chronic idiopathic neck pain. This group also displayed a significantly higher psychological burden and poorer sleep than patients with chronic tinnitus only and healthy controls. Signs and symptoms of central sensitization were also shown to be associated with tinnitus impact, pain-related disability, psychological burden and sleep disturbances. This study shows preliminary evidence for the presence of central sensitization in patients with chronic tinnitus+chronic idiopathic neck pain. This could be explained by the higher perceived tinnitus impact, psychological burden and sleep problems in this group. Trial registration: This study is registered as NCT05186259 (www.clinicaltrials.gov).

Sexual Dimorphism in the Mechanism of Pain Central Sensitization

It has long been recognized that men and women have different degrees of susceptibility to chronic pain. Greater recognition of the sexual dimorphism in chronic pain has resulted in increasing numbers of both clinical and preclinical studies that have identified factors and mechanisms underlying sex differences in pain sensitization. Here, we review sexually dimorphic pain phenotypes in various research animal models and factors involved in the sex difference in pain phenotypes. We further discuss putative mechanisms for the sexual dimorphism in pain sensitization, which involves sex hormones, spinal cord microglia, and peripheral immune cells. Elucidating the sexually dimorphic mechanism of pain sensitization may provide important clinical implications and aid the development of sex-specific therapeutic strategies to treat chronic pain.

Central sensitization syndrome in patients with rotator cuff tear: prevalence and associated factors

INTRODUCTION

A significant number of rotator cuff tear (RCT) patients developed chronic shoulder pain that did not correspond to physiological changes. Central sensitization syndrome (CSS) is a neurophysiological adaptation process that can result in hypersensitivity to peripheral stimuli. Although there is evidence of an association between CSS and musculoskeletal problems, no studies have focused on the association between CSS and RCT. The primary purpose of this study was to examine the prevalence of CSS in patients with RCT. The secondary purpose was to document the associated conditions and comorbidity that were associated with the CSS.

METHODS

This was a cross-sectional study of patients with RCT who completed the Central Sensitization Inventory (CSI). Patients with score of ≥ 40/100 were considered positive for CSS. Demographic and clinical data and CSI results were collected to analyze the prevalence and associated factors of CSS in RCT patients.

RESULTS

A total of 404 RCT patients were included, and the CSS prevalence was 39.4%. Compared to the non-CSS group, the CSS group had an odds ratio of 4.13 (95% CI, 2.70-6.32; p＜0.001) for ages 51-60, 3.07 (95% CI, 2.00-4.69; p＜0.001) for symptoms lasting more than 6 months, 6.08 (95% CI, 3.90-9.47; p＜0.001) for nonphysical laborers, 3.69 (95%CI, 2.42-5.61; p＜0.001) for long head of biceps (LHB) abnormality, 2.93 (95% CI, 1.93-4.45; p＜0.001) for concurrent shoulder stiffness, 4.82 (95% CI, 2.55-9.10; p＜0.001) for anxiety or panic episodes, and 2.11 (95% CI, 1.12, 4.00; p＜0.001) for depression.

CONCLUSIONS

The prevalence of CSS in patients with RCT was relatively high at 39.4%. The CSS was associated with higher age, female gender, and clinical findings of symptoms lasting over six months, nonphysical laborers, abnormal LHB, concurrent shoulder stiffness, anxiety, and depression.

Central sensitization in CRPS patients with widespread pain: a cross-sectional study

OBJECTIVE

Widespread pain hypersensitivity and enhanced temporal summation of pain (TSP) are commonly reported in patients with complex regional pain syndrome (CRPS) and discussed as proxies for central sensitization. This study aimed to directly relate such signs of neuronal hyperexcitability to the pain phenotype of CRPS patients.

METHODS

Twenty-one CRPS patients and 20 healthy controls (HC) were recruited. The pain phenotype including spatial pain extent (assessed in % body surface) and intensity were assessed and related to widespread pain hypersensitivity, TSP, and psychological factors. Quantitative sensory testing (QST) was performed in the affected, the contralateral and a remote (control) area.

RESULTS

CRPS patients showed decreased pressure pain thresholds in all tested areas (affected: t(34)  = 4.98, P < .001, contralateral: t(35) = 3.19, P = .005, control: t(31) = 2.65, P = .012). Additionally, patients showed increased TSP in the affected area (F(3,111) = 4.57, P = .009) compared to HC. TSP was even more enhanced in patients with a high compared to a low spatial pain extent (F(3,51) = 5.67, P = .008), suggesting pronounced spinal sensitization in patients with extended pain patterns. Furthermore, the spatial pain extent positively correlated with the Bath Body Perception Disturbance Scale (ρ = 0.491; P = .048).

CONCLUSIONS

Overall, we provide evidence that the pain phenotype in CRPS, that is, spatial pain extent, might be related to sensitization mechanism within the central nociceptive system. This study points towards central neuronal excitability as a potential therapeutic target in patients with more widespread CRPS.