An Observational Study Comparing Fibromyalgia and Chronic Low Back Pain in Somatosensory Sensitivity, Motor Function and Balance

Peak alpha frequency is related to the degree of widespread pain, but not pain intensity or duration, among people with urologic chronic pelvic pain syndrome

Introduction

Effective prevention and management strategies for chronic pain remain elusive. This has prompted investigations into biomarkers to better understand the mechanisms underlying pain development and persistence. One promising marker is low peak alpha frequency (PAF), an electroencephalography (EEG) measure that has been associated with increased sensitivity during acute experimental pain. However, findings regarding the relationship between PAF and chronic pain are variable, potentially due to disparate levels of central sensitization among chronic pain populations. This is evidenced by the variable extent of widespread pain, a phenotypic marker for central sensitization, observed across individuals with chronic pain.

Objective

To explore the impact of widespread pain on PAF among people with chronic pain.

Method

Thirty-eight individuals with urologic chronic pelvic pain syndrome were categorized as having widespread (n = 24) or localized (n = 14) pain based upon self-reported body maps. Electroencephalography data were collected under resting conditions, and PAF was determined using spectral analysis.

Results

Participants with widespread pain had a significantly lower global average PAF than those with localized pain, after controlling for age and sex. This relationship persisted even when accounting for pain intensity and duration. Peak alpha frequency differences were observed across all EEG electrodes, particularly in the sensorimotor and occipital regions.

Conclusion

Preliminary findings suggest that PAF may represent a potential biomarker for central sensitization in chronic pain, highlighting the importance of considering pain distribution in chronic pain research. Future studies with larger samples should investigate the neural mechanisms underlying these observations and the clinical utility of PAF in diverse chronic pain populations.

Peak alpha frequency differs between chronic back pain and chronic widespread pain

BACKGROUND

Low peak alpha frequency (PAF) is an electroencephalography (EEG) outcome associated reliably with high acute pain sensitivity. However, existing research suggests that the relationship between PAF and chronic pain is more variable. This variability could be attributable to chronic pain groups typically being examined as homogenous populations, without consideration being given to potential diagnosis-specific differences. Indeed, while emerging work has compared individuals with chronic pain to healthy controls, no previous studies have examined differences in PAF between diagnoses or across chronic pain subtypes.

METHODS

To address this gap, we reanalysed a dataset of resting state EEG previously used to demonstrate a lack of difference in PAF between individuals with chronic pain and healthy controls. In this new analysis, we separated patients by diagnosis before comparing PAF across three subgroups: chronic widespread pain (n = 30), chronic back pain (n = 38), and healthy controls (n = 87).

RESULTS

We replicate the original finding of no significant difference between chronic pain groups and controls, but also find that individuals with widespread pain had significantly higher global average PAF values than those of people with chronic back pain [p = 0.028, β = 0.25 Hz] after controlling for age, sex, and depression.

CONCLUSIONS

These novel findings reveal PAF values in individuals with chronic pain may be diagnosis-specific and not uniformly shifted from the values of healthy controls. Future studies should account for diagnosis and be cautious with exploring homogenous 'chronic pain' classifications during investigations of PAF.

SIGNIFICANCE

Our work suggests that, contrary to previous hypotheses, inter-individual differences in PAF reflect diagnosis-specific mechanisms rather than the general presence of chronic pain, and therefore may have important implications for future work regarding individually-tailored pain management strategies.

What are the functional and clinical characteristics shared by fibromyalgia and low back pain? A scoping review

BACKGROUND

Fibromyalgia and chronic primary low back pain are two chronic pain conditions with a significant biopsychosocial burden. Recently, the International Association for the Study of Pain has grouped them under the term chronic primary pain. To further explore similarities and differences between these two conditions, the objective of this scoping review is to explore the pain-related, physiological and psychological outcomes in individuals with fibromyalgia and low back pain.

METHODS

The following databases were used to find relevant studies, using the PRISMA guidelines: Medline, Psycinfo, and CINAHL. Studies were included if they encompassed both participants with fibromyalgia or low back pain, with the objective to compare pain-related, physiological and/or psychological outcomes.

RESULTS

Nineteen studies were selected for extraction. Among the 2801 participants, 968 had fibromyalgia (mean age 48.56 ± 7.97 years, with 94% being female) and 896 had low back pain (mean age 47.48 ± 8.15 years, with 80% being female). Pain sensitivity, physical dysfunction, illness perception, psychological distress, alexithymia, depression, and anxiety were generally more severe in participants with fibromyalgia. Most studies found similar levels of pain intensity, kinesiophobia, quality of pain, quality of life, impact of pain, suicidal risk, anger, and social support comparing individuals with fibromyalgia and individuals with low back pain.

DISCUSSION

This scoping review highlights that although both conditions show similar pain intensity and impact on quality of life, fibromyalgia is associated with greater overall severity than low back pain, especially in sensitivity to pain and depression/anxiety.

Relationship of Pain, Depression, Fatigue, and Sleep Problems with Functional Capacity, Balance, and Fear of Falling in Women with Fibromyalgia: Cross-Sectional Study

(1) Background: Fibromyalgia (FM) is a syndrome marked by chronic widespread pain, fatigue, sleep issues, and other symptoms. Interventions like physical exercise can potentially enhance physical function in individuals with FM. This study aimed to assess physical function, perceived physical fitness, balance confidence, and fear of falling in women with FM based on their levels of pain, depression, fatigue, and sleep problems. (2) Methods: Participants underwent a series of tests and questionnaires to evaluate physical and perceptual aspects. These included the Time Up and Go, Four Step Square Test, 6-Minute Walking Test, Maximum Handgrip Strength, Back Scratch, International Fitness Scale, Activities-Specific Balance Confidence Scale, and Fall Efficacy Scale-International. Participants were categorised by the severity of their pain, depression, fatigue, and sleep problems (mild, moderate, severe). A Kruskal-Wallis test assessed intergroup differences, while Spearman's rho evaluated correlations between the study variables and symptom levels. (3) Results: Perceived physical condition varied significantly with symptom severity. Symptoms and sleep problems were notably linked to fear of falling, though no significant differences emerged in the physical tests. (4) Conclusions: In women with fibromyalgia, symptom severity was primarily related to perceptual and subjective aspects of physical condition and fall safety.

Physical Function, Self-Perceived Physical Fitness, Falls, Quality of Life and Degree of Disability According to Fear and Risk of Falling in Women with Fibromyalgia

Background: People with fibromyalgia (FM) experience a range of symptoms (chronic widespread pain, fatigue, mood disorder, sleep problems, muscle stiffness) that promote deterioration of physical condition and function. With impaired physical function, fear of falling and risk of falling increases. This study evaluated physical function, self-perceived physical fitness, falls, quality of life, and the degree of disability caused by FM according to fear and risk of falling in Spanish adult women with FM. Methods: Cross-sectional study involving 84 Spanish adult women with FM. Participants completed tests to assess their physical function and completed questionnaires to evaluate self-perceived physical fitness, falls, the disabling effect of FM, quality of life, fear of falling, and risk of falling. Nonparametric statistical tests were used to analyze possible intergroup differences (Mann-Whitney U test) and correlations between variables (Spearman's Rho). Results: Women with a fear of falling and at risk of falling presented a worse performance in physical tests, worse self-perceived physical fitness, greater number of falls, lower quality of life, and greater degree of disability due to FM. Weak and moderate correlations were found for fear of falling and fall risk and the variables of interest. However, no intergroup differences were found, nor significant correlations in all variables. Conclusions: Women with FM who present fear of falling and risk of falling tend to have worse performance in physical function tests, in addition to worse self-perceived physical fitness, higher number of falls, poorer quality of life, and greater disabling effect of FM.

Facial recognition, laterality judgement, alexithymia and resulting central nervous system adaptations in chronic primary headache and facial pain-A systematic review and meta-analysis

INTRODUCTION

Patients with chronic headaches and chronic oro-facial pain commonly present psychosocial issues that can affect social interactions. A possible reason could be that patients with these disorders might present impairments in facial recognition, laterality judgement and also alexithymia. However, a systematic review summarizing the effects of facial emotion recognition, laterality judgement and alexithymia in individuals with headaches and oro-facial pain is still not available.

AIM

The main objective of this systematic review (SR) and meta-analysis (MA) was to compile and synthesize the evidence on the occurrence of alexithymia, deficits in laterality or left-right (LR) recognition and/or facial emotion recognition (FER) in patients with chronic headache and facial pain.

METHODS

Electronic searches were conducted in five databases (up to September 2023) and a manual search to identify relevant studies. The outcomes of interest were alexithymia scores, speed and accuracy in LR and/or FER, or any other quantitative data assessing body image distortions. The screening process, data extraction, risk of bias and data analysis were performed by two independent assessors following standards for systematic reviews.

RESULTS

From 1395 manuscripts found, only 34 studies met the criteria. The overall quality/certainty of the evidence was very low. Although the results should be interpreted carefully, individuals with chronic headaches showed significantly higher levels of alexithymia when compared to healthy individuals. No conclusive results were found for the other variables of interest.

CONCLUSION

Although the overall evidence from this review is very low, people with chronic primary headaches and oro-facial pain could be regularly screened for alexithymia to guarantee appropriate management.

The Role of Back Muscle Dysfunctions in Chronic Low Back Pain: State-of-the-Art and Clinical Implications

Changes in back muscle function and structure are highly prevalent in patients with chronic low back pain (CLBP). Since large heterogeneity in clinical presentation and back muscle dysfunctions exists within this population, the potential role of back muscle dysfunctions in the persistence of low back pain differs between individuals. Consequently, interventions should be tailored to the individual patient and be based on a thorough clinical examination taking into account the multidimensional nature of CLBP. Considering the complexity of this process, we will provide a state-of-the-art update on back muscle dysfunctions in patients with CLBP and their implications for treatment. To this end, we will first give an overview of (1) dysfunctions in back muscle structure and function, (2) the potential of exercise therapy to address these dysfunctions, and (3) the relationship between changes in back muscle dysfunctions and clinical parameters. In a second part, we will describe a framework for an individualised approach for back muscle training in patients with CLBP.

Distinctive alterations in the functional anatomy of the cerebral cortex in pain-sensitized osteoarthritis and fibromyalgia patients

Background

Pain-sensitized osteoarthritis and fibromyalgia patients characteristically show nociceptive system augmented responsiveness as a common feature. However, sensitization can be originally related to the peripheral injury in osteoarthritis patients, whereas pain and bodily discomfort spontaneously occur in fibromyalgia with no apparent origin. We investigated the distinct functional repercussion of pain sensitization in the cerebral cortex in both conditions.

Methods

Thirty-one pain-sensitized knee osteoarthritis patients and 38 fibromyalgia patients were compared with matched control groups. And new samples of 34 sensitized knee osteoarthritis and 63 fibromyalgia patients were used to directly compare each condition. A combined measure of local functional connectivity was estimated to map functional alterations in the cerebral cortex at rest.

Results

In osteoarthritis, weaker local connectivity was identified in the insula, which is a cortical area processing important aspects of the brain response to painful stimulation. In contrast, fibromyalgia patients showed weaker connectivity in the sensorimotor cortex extensively affecting the cortical representation of the body.

Conclusions

In osteoarthritis, weaker insular cortex connectivity is compatible with reduced neural activity during metabolic recovery after repeated activation. In the fibromyalgia neurophysiological context, weaker connectivity may better express both reduced neural activity and increased excitability, particularly affecting the sensorimotor cortex in patients with spontaneous body pain. Such a combination is compatible with a central gain enhancement mechanism, where low sensory tolerance results from the over-amplification of central sensory reception to compensate a presumably weak sensory input. We propose that deficient proprioception could be a factor contributing to weak sensory input.

Cervical Joint Position Sense and Its Correlations with Postural Stability in Subjects with Fibromyalgia Syndrome

Cervical joint position sense (JPS) and postural stability are vital to maintaining balance and preventing falls in fibromyalgia syndrome (FMS). Impaired cervical JPS may influence postural stability, and understanding the relationship between them can aid in formulating treatment strategies in individuals with FMS. This study aims to (1) assess cervical JPS and postural stability between FMS and control group and (2) determine the correlation between cervical JPS and postural stability in the FMS group. This cross-sectional study recruited 92 FMS patients (mean age: 51.52 ± 7.7 yrs.) and 92 healthy controls (mean age: 49.36 ± 6.9 yrs.). A cervical range of motion (CROM) unit was utilized to assess cervical JPS. The postural stability was assessed using an IsoFree force platform, and anterior-posterior (A/P) and medial-lateral (M/L) directions of sway and ellipse area were measured. Cervical JPS and postural stability tests were assessed and compared between FMS and control groups. Cervical JPS was significantly impaired in FMS compared to the control group (p < 0.001). The JPS errors in FMS group were larger in flexion (FMS = 5.5°, control = 2.4°), extension (FMS = 6.4°, control = 3.0°), and rotation in left (FMS = 5.4°, control = 2.2°) and right directions (FMS = 5.1°, control = 2.8°). FMS individuals demonstrated statistically significant impaired postural stability compared to control in both the dominant and non-dominant legs tested (p < 0.001). The cervical JPS test showed moderate to strong positive correlations with postural stability variables. Statistically significant correlations were observed in all the JPS directions tested with all the postural stability variables (A/P and M/L sway and ellipse area). The correlation coefficients ranged between r = 0.37 (moderate) to 0.75 (strong). Cervical JPS and postural stability are impaired in FMS individuals. A moderate to strong relationship existed between JPS and postural stability. Individuals with FMS who had a greater magnitude of cervical JPS errors exhibited more severe postural control deficits. Therefore, cervical JPS and postural stability tests should be incorporated into routine clinical practice when assessing or formulating treatment strategies for patients with FMS.

Motor cortex inhibition as a fibromyalgia biomarker: a meta-analysis of transcranial magnetic stimulation studies

Fibromyalgia (FM) is a common and refractory chronic pain condition with multiple clinical phenotypes. The current diagnosis is based on a syndrome identification which can be subjective and lead to under or over-diagnosis. Therefore, there is a need for objective biomarkers for diagnosis, phenotyping, and prognosis (treatment response and follow-up) in fibromyalgia. Potential biomarkers are measures of cortical excitability indexed by transcranial magnetic stimulation (TMS). However, no systematic analysis of current evidence has been performed to assess the role of TMS metrics as a fibromyalgia biomarker. Therefore, this study aims to evaluate evidence on corticospinal and intracortical motor excitability in fibromyalgia subjects and to assess the prognostic role of TMS metrics as response biomarkers in FM. We conducted systematic searches on PubMed/Medline, Embase, and Cochrane Central databases for observational studies and randomized controlled trials on fibromyalgia subjects that used TMS as an assessment. Three reviewers independently selected and extracted the data. Then, a random-effects model meta-analysis was performed to compare fibromyalgia and healthy controls in observational studies. Also, to compare active versus sham treatments, in randomized controlled trials. Correlations between changes in TMS metrics and clinical improvement were explored. The quality and evidence certainty were assessed following standardized approaches. We included 15 studies (696 participants, 474 FM subjects). The main findings were: (1) fibromyalgia subjects present less intracortical inhibition (mean difference (MD) = -0.40, 95% confidence interval (CI) -0.69 to -0.11) and higher resting motor thresholds (MD = 6.90 μV, 95% CI 4.16 to 9.63 μV) when compared to controls; (2) interventions such as exercise, pregabalin, and non-invasive brain stimulation increased intracortical inhibition (MD = 0.19, 95% CI 0.10 to 0.29) and cortical silent period (MD = 14.92 ms, 95% CI 4.86 to 24.98 ms), when compared to placebo or sham stimulation; (3) changes on intracortical excitability are correlated with clinical improvements - higher inhibition moderately correlates with less pain, depression, and pain catastrophizing; lower facilitation moderately correlates with less fatigue. Measures of intracortical inhibition and facilitation indexed by TMS are potential diagnostic and treatment response biomarkers for fibromyalgia subjects. The disruption in the intracortical inhibitory system in fibromyalgia also provides additional evidence that fibromyalgia has some neurophysiological characteristics of neuropathic pain. Treatments inducing an engagement of sensorimotor systems (e.g., exercise, motor imagery, and non-invasive brain stimulation) could restore the cortical inhibitory tonus in FM and induce clinical improvement.