Current understanding of nociplastic pain

Nociplastic pain by the "International Association for the Study of Pain" is defined as pain that arises from altered nociception despite no clear evidence of nociceptive or neuropathic pain. Augmented central nervous system pain and sensory processing with altered pain modulation are suggested to be the mechanism of nociplastic pain. Clinical criteria for possible nociplastic pain affecting somatic structures include chronic regional pain and evoked pain hypersensitivity including allodynia with after-sensation. In addition to possible nociplastic pain, clinical criteria for probable nociplastic pain are pain hypersensitivity in the region of pain to non-noxious stimuli and presence of comorbidity such as generalized symptoms with sleep disturbance, fatigue, or cognitive problems with hypersensitivity of special senses. Criteria for definitive nociplastic pain is not determined yet. Eight specific disorders related to central sensitization are suggested to be restless leg syndrome, chronic fatigue syndrome, fibromyalgia, temporomandibular disorder, migraine or tension headache, irritable bowel syndrome, multiple chemical sensitivities, and whiplash injury; non-specific emotional disorders related to central sensitization include anxiety or panic attack and depression. These central sensitization pain syndromes are overlapped to previous functional pain syndromes which are unlike organic pain syndromes and have emotional components. Therefore, nociplastic pain can be understood as chronic altered nociception related to central sensitization including both sensory components with nociceptive and/or neuropathic pain and emotional components. Nociplastic pain may be developed to explain unexplained chronic pain beyond tissue damage or pathology regardless of its origin from nociceptive, neuropathic, emotional, or mixed pain components.

Antimicrobial therapies for chronic pain (part 2): the prevention and treatment of chronic pain

The discovery and development of antimicrobial therapies represents one of the most significant advancements in modern medicine. Although the primary therapeutic intent of antimicrobials is to eliminate their target pathogens, several antimicrobials have been shown to provide analgesia as a secondary benefit. Antimicrobials have demonstrated analgesic effects in conditions that involve dysbiosis or potential subclinical infection (e.g ., chronic low back pain with Modic type 1 changes; chronic prostatitis/chronic pelvic pain; irritable bowel syndrome; inflammatory bowel disease; functional gastrointestinal disorders/dyspepsia; myalgic encephalomyelitis/chronic fatigue syndrome), and might even prevent the chronification of pain after acute infections that are associated with excessive systemic inflammation (e.g ., post COVID-19 condition/long Covid, rheumatic fever). Clinical studies often assess the analgesic effects of antimicrobial therapies in an observational manner, without the ability to identify causative relationships, and significant gaps in the understanding remain regarding the analgesic potential of antimicrobials. Numerous interrelated patient-specific, antimicrobial-specific, and disease-specific factors altogether contribute to the perception and experience of pain, and each of these requires further study. Given worldwide concerns regarding antimicrobial resistance, antimicrobials must continue to be used judiciously and are unlikely to be repurposed as primary analgesic medications. However, when equipoise exists among several antimicrobial treatment options, the potential analgesic benefits of certain antimicrobial agents might be a valuable aspect to consider in clinical decision-making. This article (the second in a two-part series) aims to comprehensively review the evidence on the prevention and treatment of chronic pain using antimicrobial therapies and suggest a framework for future studies on this topic.

Antimicrobial therapies for chronic pain (part 1): analgesic mechanisms

There is increasing evidence that the relationship between chronic pain and infections is complex and intertwined. Bacterial and viral infections can cause pain through numerous mechanisms such as direct tissue damage and inflammation, the induction of excessive immunologic activity, and the development of peripheral or central sensitization. Treating infections might relieve pain by attenuating these processes, but a growing body of literature suggests that some antimicrobial therapies confer analgesic effects, including for nociceptive and neuropathic pain symptoms, and affective components of pain. The analgesic mechanisms of antimicrobials are indirect, but might be conceptualized into two broad categories: 1) the reduction of the infectious burden and associated pro-inflammatory processes; and 2) the inhibition of signaling processes (e.g., enzymatic and cytokine activity) necessary for nociception and maladaptive neuroplastic changes via off-target effects (unintended binding sites). For the former, there is evidence that symptoms of chronic low back pain (when associated with Modic type 1 changes), irritable bowel syndrome, inflammatory bowel disease, chronic pelvic pain, and functional dyspepsia might be improved after antibiotic treatment, though significant questions remain regarding specific regimens and dose, and which subpopulations are most likely to benefit. For the latter, there is evidence that several antimicrobial classes and medications exert analgesic effects independent of their reduction of infectious burden, and these include cephalosporins, ribavirin, chloroquine derivatives, rapalogues, minocycline, dapsone, and piscidin-1. This article aims to comprehensively review the existing literature for antimicrobial agents that have demonstrated analgesic efficacy in preclinical or clinical studies.

Comparison of the effects of transcutaneous electrical nerve stimulation and interferential current therapies in central sensitization in patients with knee osteoarthritis

Background

This study is primarily aimed to determine whether transcutaneous electrical nerve stimulation (TENS) and interferential current (IFC) treatments have any effect on central sensitization (CS) in patients with knee osteoarthritis (OA) and to investigate which treatment is more effective.

Methods

In this randomized controlled trial, 80 patients were randomized into four treatment groups: TENS, Plasebo-TENS, IFC, and Plasebo-IFC. All interventions were applied 5 times a week for 2 weeks. Primary outcome was pressure pain threshold (PPT), which is accepted as the objective indicator of CS, at the painful knee and at the shoulder as a painless distant point. Other outcome measures were the visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index, Timed Up and Go Test, pain catastrophizing scale, Beck Depression Inventory, and Tampa Scale of Kinesiophobia.

Results

All assessment parameters were improved, without a significant difference among the groups except PPT. PPT scores were significantly improved in TENS and IFC groups when compared with the sham groups at 2 weeks and 3 months. In addition, this improvement was even more pronounced in the TENS group. Multivariable logistic regression analysis showed that the patient's inclusion in the TENS group, an initial high PPT, and an initial low VAS score were independent risk factors for improvement in the PPT.

Conclusions

This study shows that TENS and IFC reduced pain sensitivity as compared to placebo groups in patients with knee OA. This effect was more pronounced in the TENS group.

The effect of graded motor imagery training on pain, functional performance, motor imagery skills, and kinesiophobia after total knee arthroplasty: randomized controlled trial

Background

The aim was to investigate the effect of graded motor imagery (GMI) added to rehabilitation on pain, functional performance, motor imagery ability, and kinesiophobia in individuals with total knee arthroplasty (TKA).

Methods

Individuals scheduled for unilateral TKA were randomized to one of two groups: control (traditional rehabilitation, n = 9) and GMI (traditional rehabilitation + GMI, n = 9) groups. The primary outcome measures were the visual analogue scale and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Secondary outcome measures were knee range of motion, muscle strength, the timed up and go test, mental chronometer, Movement Imagery Questionnaire-3, lateralization performance, Central Sensitization Inventory, Pain Catastrophizing Scale, and Tampa Kinesiophobia Scale. Evaluations were made before and 6 weeks after surgery.

Results

Activity and resting pain were significantly reduced in the GMI group compared to the control group (P < 0.001 and P = 0.004, respectively). Movement Imagery Questionnaire-3 scores and accuracy of lateralization performance also showed significant improvement (P = 0.037 and P = 0.015, respectively). The Pain Catastrophizing Scale and Tampa Kinesiophobia Scale scores were also significantly decreased in the GMI group compared to the control group (P = 0.039 and P = 0.009, respectively). However, GMI did not differ significantly in WOMAC scores, range of motion, muscle strength, timed up and go test and Central Sensitization Inventory scores compared to the control group (P > 0.05).

Conclusions

GMI improved pain, motor imagery ability, pain catastrophizing, and kinesiophobia in the acute period after TKA.

Musculoskeletal Pain, a Possible Indicator of Central Sensitization, Is Positively Associated With Lower Urinary Tract Symptom Progression in Community-Dwelling Older Men

BACKGROUND

Musculoskeletal pain, a possible marker of central sensitization, is associated with higher prevalence of lower urinary tract symptoms (LUTS) among older men. We investigated whether musculoskeletal pain is associated with LUTS progression.

METHODS

Participants were 5 569 men age ≥65 years enrolled in the prospective, multicenter Osteoporotic Fractures in Men (MrOS) Study. Self-reported musculoskeletal pain within 12 months before baseline was categorized as any pain and multilocation pain. Pain interference within 4 weeks of baseline was assessed with the SF-12 questionnaire. LUTS were assessed repeatedly with the American Urological Association Symptom Index (AUA-SI). Men with severe LUTS at baseline were excluded. LUTS progression was defined as the first occurrence of a ≥4-point AUA-SI increase during a 2-year follow-up interval. Incidence rate ratios (IRR) and 95% confidence intervals (CI) were estimated using multivariable pooled logistic regression.

RESULTS

LUTS progression was 37% higher among men with any musculoskeletal pain compared with men without pain (IRR 1.37, 95% CI: 1.21, 1.54). Positive associations were also observed between LUTS progression and pain at 1 (IRR 1.31, 95% CI: 1.13, 1.48) and ≥2 locations (IRR 1.42, 95% CI: 1.24, 1.60). Compared with men without pain interference, men with quite a bit/extreme pain interference were most likely to experience LUTS progression (minimal interference IRR 1.15, 95% CI: 1.03, 1.26; moderate interference IRR 1.28, 95% CI: 1.11, 1.45; quite a bit/extreme interference IRR 1.47, 95% CI: 1.22, 1.71).

CONCLUSIONS

Among men initially without severe LUTS, musculoskeletal pain is associated with an increased risk of LUTS progression. Studies using validated measures of central sensitization and LUTS progression among men are warranted.

The Neurophysiological Lesion: A Scoping Review

Objective

The purpose of this study was to examine the extent of the literature on the neurophysiological lesion as referenced in functional neurology.

Methods

A literature search was performed within the period from 2010 to March 2021. Search terms included central sensitization, central sensitivity syndrome, nociplastic pain, cold hyperalgesia, heat hyperalgesia, mechanical hyperalgesia, dynamic mechanical allodynia, temporal summation, spatial summation, and descending inhibition. A qualitative synthesis summarized the research findings, including clinical conditions and effect of spinal manipulation.

Results

There were 30 studies, which included 7 high-level studies (meta-analysis or systematic reviews), 22 randomized controlled studies, and 1 scoping review. The findings suggest the existence of the changes in the central integrated state of a population of neurons with various disorders, experimentally induced stimulation, and treatment. The current literature suggests plasticity of the central integrative state (CIS) with the onset of pathologies and the changes in the CIS with different conservative nonpharmacologic treatments.

Conclusions

This review suggests changes in the resting state of the CIS of a population of neurons that exist in the physiologic lesion may change in response to various therapies, including manipulative therapy. The findings from this review provide support of the hypothesis that nonpharmacologic conservative care may affect the neurophysiological lesion. However, studies were heterogeneous and evidence was lacking in the translation of targeting the therapies to distinct neuronal areas for clinical outcomes to treat specific disease states.

Pelvic Pain Comorbidities Associated with Quality-of-life after Endometriosis Surgery

BACKGROUND

After endometriosis surgery, pain can persist or recur in a subset of patients. A possible reason for persistent pain post-surgery is central nervous system sensitization and associated pelvic pain comorbidities. Surgery addresses the peripheral component of endometriosis pain pathophysiology (by lesion removal) but may not treat this centralized pain. Therefore endometriosis patients with pelvic pain comorbidities related to central sensitization may experience worse pain-related outcomes after surgery, such as lower pain-related quality-of-life.

OBJECTIVE

To determine whether baseline (preoperative) pelvic pain comorbidities are associated with pain-related quality-of-life at follow-up after endometriosis surgery.

STUDY DESIGN

This study utilized longitudinal prospective registry data from the Endometriosis and Pelvic Pain Interdisciplinary Cohort at the BC Women's Center for Pelvic Pain and Endometriosis. Subjects were ≤ 50 years old with confirmed or clinically suspected endometriosis, who underwent surgery (fertility-sparing or hysterectomy) for endometriosis pain. Subjects completed the pain subscale of the Endometriosis Health Profile (EHP-30) quality-of-life questionnaire preoperatively and at follow-up (1-2 years). Linear regression was performed to measure the individual relationships between seven pelvic pain comorbidities at baseline and follow-up EHP-30 score, controlling for baseline EHP-30 and type of surgery received. These baseline (preoperative) pelvic pain comorbidities included abdominal wall pain, pelvic floor myalgia, painful bladder syndrome, irritable bowel syndrome, Patient Health Questionnaire (PHQ-9) depression score, General Anxiety Disorder (GAD-7) score, and Pain Catastrophizing Scale (PCS) score. LASSO regression was then performed to select the most important variables associated with follow-up EHP-30 from among seventeen covariates (including the seven pelvic pain comorbidities, baseline EHP-30 score, type of surgery, and other endometriosis-related factors such as stage and histologic confirmation of endometriosis). Using 1000 bootstrap samples, we estimated the coefficients and confidence intervals of the selected variables and generated a covariate importance rank.

RESULTS

The study included 444 subjects. The median follow-up time was 18 months. Pain-related quality-of-life (EHP-30) of the study population significantly improved at follow-up after surgery (p<0.001). The following pelvic pain comorbidities were associated with lower quality-of-life (higher EHP-30 score) after surgery controlling for baseline EHP-30 score and type of surgery (fertility-sparing vs. hysterectomy): abdominal wall pain (p=0.013), pelvic floor myalgia (p=0.036), painful bladder syndrome (p=0.022), PHQ-9 score (p<0.001), GAD-7 score (p<0.001), and PCS score (p=0.007). Irritable bowel syndrome was not significant (p=0.70). Of the seventeen covariates included for LASSO regression, six remained in the final model (lambda = 3.136). These included three pelvic pain comorbidities that were associated with higher follow-up EHP-30 scores or worse quality-of-life: abdominal wall pain (β = 3.19), pelvic floor myalgia (β = 2.44), and PHQ-9 depression score (β = 0.49). The other three variables in the final model were baseline EHP-30 score, type of surgery, and histologic confirmation of endometriosis.

CONCLUSION

Pelvic pain comorbidities present at baseline before surgery, which may reflect underlying central nervous system sensitization, are associated with lower pain-related quality-of-life after endometriosis surgery. Particularly important were depression and musculoskeletal/myofascial pain (abdominal wall pain and pelvic floor myalgia). Therefore, these pelvic pain comorbidities should be candidates for a formal prediction model of pain outcomes after endometriosis surgery.

Primary somatosensory cortex and periaqueductal gray functional connectivity as a marker of the dysfunction of the descending pain modulatory system in fibromyalgia

Background

Resting-state functional connectivity (rs-FC) may aid in understanding the link between pain-modulating brain regions and the descending pain modulatory system (DPMS) in fibromyalgia (FM). This study investigated whether the differences in rs-FC of the primary somatosensory cortex in responders and non-responders to the conditioned pain modulation test (CPM-test) are related to pain, sleep quality, central sensitization, and the impact of FM on quality of life.

Methods

This cross-sectional study included 33 females with FM. rs-FC was assessed by functional magnetic resonance imaging. Change in the numerical pain scale during the CPM-test assessed the DPMS function. Subjects were classified either as non-responders (i.e., DPMS dysfunction, n = 13) or responders (n = 20) to CPM-test. A generalized linear model (GLM) and a receiver operating characteristic (ROC) curve analysis were performed to check the accuracy of the rs-FC to differentiate each group.

Results

Non-responders showed a decreased rs-FC between the left somatosensory cortex (S1) and the periaqueductal gray (PAG) (P < 0.001). The GLM analysis revealed that the S1-PAG rs-FC in the left-brain hemisphere was positively correlated with a central sensitization symptom and negatively correlated with sleep quality and pain scores. ROC curve analysis showed that left S1-PAG rs-FC offers a sensitivity and specificity of 85% or higher (area under the curve, 0.78, 95% confidence interval, 0.63-0.94) to discriminate who does/does not respond to the CPM-test.

Conclusions

These results support using the rs-FC patterns in the left S1-PAG as a marker for predicting CPM-test response, which may aid in treatment individualization in FM patients.

Imbalance in the spinal serotonergic pathway induces aggravation of mechanical allodynia and microglial activation in carrageenan inflammation

Background

This study investigated the effect of an excess and a deficit of spinal 5-hydroxytryptamine (5-HT) on the mechanical allodynia and neuroglia activation in a rodent pain model of carrageenan inflammation.

Methods

Male Sprague-Dawley rats were implanted with an intrathecal (i.t.) catheter to administer the drug. To induce an excess or deficit of 5-HT in the spinal cord, animals were given either three i.t. 5-HT injections at 24-hour intervals or a single i.t. injection of 5,7-dihydroxytryptamine (5,7-DHT) before carrageenan inflammation. Mechanical allodynia was measured using the von Frey test for 0-4 hours (early phase) and 24-28 hours (late phase) after carrageenan injection. The changes in the activation of microglia and astrocyte were examined using immunofluorescence of the dorsal horn of the lumbar spinal cord.

Results

Both an excess and a deficit of spinal 5-HT had no or a minimal effect on the intensity of mechanical allodynia during the early phase but prevented the attenuation of mechanical allodynia during the late phase, which was observed in animals not treated with i.t. 5-HT or 5,7-DHT. Animals with an excess or deficit of 5-HT showed stronger activation of microglia, but not astrocyte, during the early and late phases, than did normal animals.

Conclusions

Imbalance in the descending 5-HT pathway in the spinal cord could aggravate the mechanical allodynia and enhance the activation of microglia, suggesting that the spinal 5-HT pathway plays an essential role in maintaining the nociceptive processing in balance between facilitation and inhibition in inflammatory pain caused by carrageenan inflammation.

An investigation of the relationship between cutaneous allodynia and kinesiophobia, gastrointestinal system symptom severity, physical activity and disability in individuals with migraine

Background

To investigate the relationship between cutaneous allodynia (CA) and kinesiophobia, gastrointestinal system (GIS) symptom severity, physical activity, and disability, and to determine whether CA, pain, and disability were influencing factors for kinesiophobia, GIS symptoms, and physical activity in individuals with migraine.

Methods

The study included 144 individuals with migraine. CA, kinesiophobia, GIS symptoms, physical activity level, and migraine-related disability were evaluated with the Allodynia Symptom Checklist, the Tampa Kinesiophobia Scale (TKS), the Gastrointestinal Symptom Rating Scale (GSRS), the International Physical Activity Questionnaire-7, and the Migraine Disability Assessment Scale (MIDAS), respectively.

Results

The CA severity was only associated with TKS (r = 0.515; P < 0.001), GSRS-total (r = 0.336; P < 0.001), GSRS-abdominal pain (r = 0.323; P < 0.001), GSRS-indigestion (r = 0.257; P = 0.002), GSRS-constipation (r = 0.371; P < 0.001), and MIDAS scores (r = 0.178; P = 0.033). Attack frequency (P = 0.015), attack duration (P = 0.035) and presence of CA (P < 0.001) were risk factors for kinesiophobia. Attack frequency (P = 0.027) and presence of CA (P = 0.004) were risk factors for GIS symptoms.

Conclusions

There was a relationship between the CA and kinesiophobia, GIS symptoms, and disability. CA and attack frequency were found to be risk factors for kinesiophobia and GIS symptoms. Migraine patients with CA should be assessed in terms of kinesiophobia, GIS, and disability. Lifestyle changes such as exercise and dietary changes and/or pharmacological treatment options for CA may increase success in migraine management.

Relationships of autonomic dysfunction with disease severity and neuropathic pain features in fibromyalgia: is it really a sympathetically maintained neuropathic pain?

Background

The pathophysiology of fibromyalgia (FM) involves many mechanisms including central nervous system sensitization theory, autonomic nervous system (ANS) dysfunction, and recently small fiber neuropathy. While the small fiber neuropathy itself can cause ANS dysfunction and neuropathic pain (NP), it is still unknown whether ANS problems have an association with severity of disease and NP in patients with FM. The aim of this study was to evaluate ANS dysfunction in FM patients and to explore possible associations of ANS dysfunction with disease severity and NP.

Methods

Twenty-nine FM patients and 20 healthy controls were included in this cross-sectional study. Participants were tested using sympathetic skin responses (SSR) and R-R interval variation analyses for sympathetic and parasympathetic ANS dysfunction, respectively. Disease severity and somatic symptoms of patients with FM were evaluated using the ACR-2010 scales and Fibromyalgia Impact Questionnaire, and NP symptoms were evaluated using the Pain Detect Questionnaire and Douleur Neuropathique questionnaire.

Results

FM patients were found to have ANS dysfunction characterized by increased sympathetic response and decreased parasympathetic response. SSR amplitudes were found to be correlated with a more severe disease. Although non-significant, NP severity tended to be associated with a decrease in sympathetic and parasympathetic activities.

Conclusions

ANS dysfunction may play a role in the pathophysiology of FM. The trend of decreased ANS functions in FM patients exhibiting NP contradicts the notion that FM is a sympathetically maintained NP and may be explained with small fiber involvement.

Effectiveness of graded motor imagery in subjects with frozen shoulder: a pilot randomized controlled trial

Background

Subjects with frozen shoulder (FS) might not be comfortable with vigorous physical therapy. Clinical trials assessing the effect of graded motor imagery (GMI) in FS are lacking. The aim of this study was to determine the effect of GMI as an adjunct to conventional physiotherapy in individuals with painful FS.

Methods

Twenty subjects aged 40–65 years having stage I and II of FS were randomly divided into two study groups. The conventional physiotherapy group (n = 10) received electrotherapy and exercises while the GMI group (n = 10) received GMI along with the conventional physiotherapy thrice a week for 3 weeks. Pre- (Session 1) and post- (Session 9) intervention analysis for flexion, abduction, and external rotation range of motion (ROM) using a universal goniometer, fear of movement using the fear avoidance belief questionnaire (FABQ), pain with the visual analogue scale, and functional disability using the shoulder pain and disability index (SPADI) was done by a blinded assessor.

Results

Statistically significant difference was seen within both the groups for all the outcomes. In terms of increasing abduction ROM as well as reducing fear of movement, pain, and functional disability, the GMI group was significantly better than control group. However, both groups were equally effective for improving flexion and external rotation ROM.

Conclusions

Addition of GMI to the conventional physiotherapy proved to be superior to conventional physiotherapy alone in terms of reducing pain, kinesiophobia, and improving shoulder function for stage I and II of FS.

Correlation Between Central Sensitization and Remote Muscle Performance in Individuals With Chronic Low Back Pain

OBJECTIVE

The purpose of this study was to examine associations between the degree of central sensitization (CS) and remote muscle performance in people with chronic low back pain (CLBP).

METHODS

The 2011 fibromyalgia (FM) criteria and severity scales (2011 FM survey) were used as a surrogate measure of CS to divide the participants into 2 groups: FM-positive CLBP and FM-negative CLBP. Measures related to central sensitization included the 2011 FM survey and pressure pain threshold of the thumbnail. Measures related to muscle performance included neck flexor muscle strength and endurance and plantar flexor muscle strength. Between-groups and correlation analyses were performed.

RESULTS

Sixty people with CLBP were enrolled (30 FM-positive, 30 FM-negative). There was no significant difference between the subgroups in age, sex, or pain duration (P > .05). The FM-positive CLBP group showed poorer neck flexor muscle endurance (P = .01) and plantar flexor muscle strength (P = .002) than the FM-negative CLBP group, whereas neck flexor muscle strength was not different between the groups (P = .175). Scores for FM and values for pressure pain thresholds of the thumbnail were associated with neck flexor muscle strength (respectively, r = -0.320, P = .013, and r = 0.467, P < .001), endurance (r = -0.242, P < .001, and r = 0.335, P = .009), and plantar flexor muscle strength (r = -0.469, P < .001, and r = 0.500, P < .001).

CONCLUSION

We found associations between the degree of CS and remote muscle strength and endurance, suggesting that poor remote muscle performance is possibly a clinical sign of CS in people with CLBP.

Pain Intensity, Pressure Pain Hypersensitivity, Central Sensitization, and Pain Catastrophizing Related to Vascular Alterations in Raynaud's Phenomenon: A Preliminary Case-Control Study

OBJECTIVE

To evaluate pain intensity, widespread pressure pain, central sensitization (CS), and catastrophizing between subjects with primary and secondary Raynaud's phenomenon (RP) and healthy controls and to compare the relationships between vascular impairment and pain perception.

METHODS

A preliminary case-control study was performed with a total sample of 57 participants (37 with RP). Sociodemographic data, clinical/vascular data, and pain variables (pain intensity, pressure pain sensitivity, pain magnitude and threshold, CS, and catastrophizing) were registered. Results were analyzed by analysis of covariance and Pearson correlation.

RESULTS

Participants with RP had a lower basal temperature (more vasoconstriction) in their hands (P ≤ 0.012), higher pain intensity (P ≤ 0.001), higher electrical pain magnitude (P < 0.001), and lower pressure pain (P ≤ 0.05) and electrical pain (P < 0.001) thresholds in comparison with healthy controls. Secondary RP participants showed a significantly higher level of CS compared with controls and primary RP participants (P = 0.001). Catastrophizing was higher in the primary and secondary RP (P ≤ 0.001) groups than in controls. No correlations were observed between severity of vasoconstriction and pain variables.

CONCLUSIONS

RP participants showed bilateral hypersensitivity to pressure pain. However, the severity of vascular alterations seems not to be related to central pain experiences. Additional mechanisms such as catastrophizing may influence pain in RP; nevertheless, central sensitization only appears to be involved in the secondary form of RP.

Pain Expansion and Severity Reflect Central Sensitization in Primary Care Patients with Greater Trochanteric Pain Syndrome

OBJECTIVES

The aims of this study were twofold: 1) to evaluate the differences in pain sensitivity of patients with greater trochanteric pain syndrome (GTPS) and 2) to examine the association between pain expansion, pain severity, and pain-related central sensitization somatosensory variables in patients with GTPS.

STUDY DESIGN

A cross-sectional study.

SETTING

Primary health care centers.

SUBJECTS

The sample consisted of 49 participants with a mean age of 48.28 ± 8.13 years and included eight males (16.3%) and 41 females (83.7%).

METHODS

Conditioned pain modulation (CPM), pain location, temporal summation, pressure pain detection threshold (PPDT), and pain intensity were recorded. Pain severity was determined with the Graded Chronic Pain Scale (GCPS).

RESULTS

Several participants (34.7%) showed a negative conditioned pain modulation and a statistically significant negative moderate correlation (P < 0.05; r = -0.316) between conditioned pain modulation and right view percentage of pain location. Temporal summation at the major trochanter showed a statistically significant low negative correlation (P < 0.05; r = -0.298). The GCPS exhibited a statistically significant moderately positive correlation (P < 0.01; r = 0.467) with the PPDT at the trochanter and a significant correlation with the postero-superior iliac spine (P < 0.01; r = 0.515) and epicondyle (P < 0.01; r = 0.566).

CONCLUSIONS

Patients with GTPS presented altered CPM, a relationship with more pain areas associated with negative CPM, and a positive association between pain severity and mechanical hyperalgesia at remote sites. Thus, physicians could apply these outcome measurements to assess primary care patients with GTPS and determine the central sensitization presence to prescribe adequate multimodal treatment approaches.

Concurrent Effects of Exercise and Curcumin on Spatial Learning and Memory in Sensitized Male Mice Following Morphine Administration

Background:

Exercise and Curcumin have positive effects on spatial memory and cognition independently. The present study aims to investigate whether the combination of ineffectual dosage of these factors can affect cognition and as a solvent if DMSO is involved in Curcumin effects.

Materials and Methods:

Male NMRI mice (1-month-old) swam (1 week) for 60 minutes (5days/week) and injected with morphine (2.5 mg/ml/kg, intraperitoneal) for five days. Spatial learning and memory were assessed by Moris Water Maze test on the 10th day after stopping morphine injection.

Results:

The findings revealed that exercise, dimethyl sulfoxide (DMSO), and Curcumin increased memory formation induced by 2.5 mg/ml/kg morphine. DMSO+exercise decreased memory formation induced by morphine, but curcumin +exercise could return the effect of DMSO on the cognition.

Conclusion:

As a solvent, DMSO had independent effects on memory, which lead to memory impairment in combination with exercise. Therefore, considering its unpredictable effects on cognitive performance, it should be replaced with another solvent or might be used carefully in behavioral experiments.

Spinal Manipulation Therapy Improves Tactile Allodynia and Peripheral Nerve Functionality and Modulates Blood Oxidative Stress Markers in Rats Exposed to Knee-Joint Immobilization

OBJECTIVE

The purpose of our study was to evaluate the effect of manually assisted lumbar spinal manipulation therapy on tactile allodynia, peripheral nerve functional recovery, and oxidative markers in rats exposed to knee immobilization-inducing hypersensitivity.

METHODS

Tactile allodynia and sciatic, tibial, and peroneal functional indices were assessed before the knee joint immobilization, 24 hours after the knee cast removal, and 24 hours after 3 weeks of lumbar therapy with the Activator Adjusting Instrument, model 4 (AAI 4). Subsequently, the blood was collected from each rat, and oxidative markers such as lipid hydroperoxide levels; nitric oxide metabolites; and superoxide dismutase, catalase, and glutathione peroxidase activities were assessed.

RESULTS

The AAI 4 improved the immobilization-induced allodynia and recovered the peripheral nerve functional indices impaired after knee immobilization. Immobilized rats treated with AAI 4 therapy presented a lack of significant changes in lipid hydroperoxides and nitric oxide metabolites in the plasma contrasting with rats that were kept freely in their cages, with no therapy applied, which presented elevated lipid hydroperoxides levels. Also, the antioxidant catalase enzymatic activity decreased in the blood of rats immobilized and treated with AAI 4.

CONCLUSION

These results suggest that manually assisted lumbar spinal manipulation therapy modulates systemic oxidative stress, which possibly contributes to the analgesia and recovery of peripheral nerve functionality.

Pericranial Tenderness in Females With Episodic Cervical Headache vs Asymptomatic Controls: A Cross-sectional Study

OBJECTIVES

The purpose of this study was to compare pericranial tenderness of females with episodic cervical headache vs matched asymptomatic controls.

METHODS

Through a single-blind, cross-sectional study, pericranial tenderness was compared between 20 females with episodic cervical headaches (29.4 ± 13.2 years) and 20 age-matched female asymptomatic controls (30.1 ± 13.7 years). Pericranial tenderness was bilaterally measured in a headache-free period with the "total tenderness score" (TTS) in the suboccipital, temporal, frontal, masseter, upper trapezius (UT), levator scapula, and sternocleidomastoid (SCM) muscle insertions. Passive cervical mobility, headache intensity, frequency, and duration were secondary outcomes. Analysis was done with a 95% confidence level (SPSS version 22). The Mann-Whitney U-test was used to compare pericranial, cephalic, cervical, and muscle-specific tenderness between groups. Correlations between passive cervical mobility and headache characteristics and the TTS were estimated with Spearman's ρ.

RESULTS

The headache group (1.25 ± 0.89) showed a 2 times higher (P < .05) pericranial TTS compared to the control group (0.62 ± 0.70). Higher (P < .05) scores were observed for the left suboccipital, temporal, masseter, UT, levator scapula, and SCM muscles and the right suboccipital, frontal, UT, and levator scapula muscles. Grouping the tenderness scores into cervical (suboccipital, UT, levator scapula, SCM) and cephalic (frontal, temporal, masseter) regions revealed greater scores (P < .05) in the headache group. In the latter, the TTS was significantly positively correlated with passive cervical extension (ρ = 0.78).

CONCLUSION

Consistent higher tenderness scores were observed and suggest involvement of sensitization in patients with episodic cervical headaches. A positive correlation was seen between passive cervical extension and sensitivity.

Association Between Symptoms of Central Sensitization and Cognitive Behavioral Factors in People With Chronic Nonspecific Low Back Pain: A Cross-sectional Study

OBJECTIVE

The objective of this cross-sectional study was to analyze the relationship between symptoms of central sensitization (CS) and important cognitive behavioral and psychosocial factors in a sample of patients with chronic nonspecific low back pain.

METHODS

Participants with chronic nonspecific low back pain for at least 3 months were included in the study. They completed several questionnaires and a functional test. Pearson's correlation was used to analyze associations between symptoms of CS and pain behavior, functioning, pain, pain catastrophizing, kinesiophobia, and illness perceptions. Additionally, a between-group analysis was performed to compare patients with and without clinically relevant symptoms of CS.

RESULTS

Data from 38 participants were analyzed. Significant associations were found between symptoms of CS and all other outcomes, especially current pain (r = 0.510, P = .001), mean pain during the past 7 days (r = 0.505, P = .001), and pain catastrophizing (r = 0.518, P = .001). Patients with clinically relevant symptoms of CS scored significantly worse on all outcomes compared with persons without relevant symptoms of CS, except on functioning (P = .128).

CONCLUSIONS

Symptoms of CS were significantly associated with psychosocial and cognitive behavioral factors. Patients exhibiting a clinically relevant degree of symptoms of CS scored significantly worse on most outcomes, compared with the subgroup of the sample with fewer symptoms of CS.

Bimodal Modulation of Ipsilateral Spinal-Coeruleo-Spinal Pathway in CRPS: A Novel Model for Explaining Different Clinical Features of the Syndrome

OBJECTIVE

The objective is to present a hypothesis to explain the sensory, autonomic, and motor disturbances associated with complex regional pain syndrome (CRPS) syndrome.

METHODS

The author reviewed the available and relevant literature, which was supplemented with research on experimental animal models, with a focus on how they may translate into humans, particularly in areas about pathophysiologic mechanisms of CRPS.

RESULTS

We propose that different CRPS subtypes may result from facilitative or inhibitory influences exerted by the spinal-coeruleo-spinal pathway in three sites at the spinal cord: the dorsal horn (DH), intermediolateral cell column (IML) and ventral horn (VH). A facilitatory influence over DH may have a pronociceptive effect that explains exacerbated pain, sensory disturbances, and spreading sensitization and neuroinflammation. Conversely, a facilitatory influence over preganglionic neurons located in IML cell column may increase sympathetic outflow with peripheral vasoconstriction, which leads to cold skin, ipsilateral limb ischaemia, and sympathetically maintained pain (SMP). For patients presenting with these symptoms, a descending inhibitory influence would be predicted to result in decreased sympathetic outflow and warm skin, as well as impairment of peripheral vasoconstrictor reflexes. Finally, a descending inhibitory influence over VH could explain muscle weakness and decreased active range of motion, while also facilitating motor reflexes, tremor and dystonia.

CONCLUSIONS

The proposed model provides a mechanistically based diagnostic scheme for classifying and explaining the sensory, autonomic and motor disturbances associated with CRPS syndrome.