Quantitative sensory testing in fibromyalgia patients and in healthy subjects: identification of subgroups

Cluster analysis in fibromyalgia: a systematic review

BACKGROUND

The multifaceted nature of Fibromyalgia syndrome (FM) symptoms has been explored through clusters analysis.

OBJECTIVE

To synthesize the cluster research on FM (variables, methods, patient subgroups, and evaluation metrics).

METHODS

We performed a systematic review following the PRISMA recommendations. Independent searches were performed on PubMed, Embase, Web of Science, and Cochrane Central, employing the terms "fibromyalgia" and "cluster analysis". We included studies dated to January 2024, using the cluster analysis to assess any physical, psychological, clinical, or biomedical variables in FM subjects, and descriptively synthesized the studies in terms of design, cluster method, and resulting patient profiles.

RESULTS

We included 39 studies. Most with a cross-sectional design aiming to classify subsets based on the severity, adjustment, symptomatic manifestations, psychological profiles, and response to treatment, based on demographic and clinical variables. Two to four different profiles were found according to the levels of severity and adjustment to FMS. According to symptom manifestation, two to three clusters described the predominance of pain versus fatigue, and thermal pain sensitivity (less versus more sensitive). Other clusters revealed profiles of personality (pathological versus non-pathological) and psychological vulnerability (suicidal ideation). Additionally, studies identified different responses to treatment (pharmacological and multimodal).

CONCLUSION

Several profiles exist within FMS population, which point out to the need for specific treatment options given the different profiles and an efficient allocation of healthcare resources. We notice a need towards more objective measures, and the validation of the cluster results. Further research might investigate some of the assumptions of these findings, which are further discussed in this paper.

Indication for spinal sensitization in chronic low back pain: mechanical hyperalgesia adjacent to but not within the most painful body area

Introduction

In 85% of patients with chronic low back pain (CLBP), no specific pathoanatomical cause can be identified. Besides primary peripheral drivers within the lower back, spinal or supraspinal sensitization processes might contribute to the patients' pain.

Objectives

The present study conceptualized the most painful area (MP) of patients with nonspecific CLBP as primarily affected area and assessed signs of peripheral, spinal, and supraspinal sensitization using quantitative sensory testing (QST) in MP, a pain-free area adjacent to MP (AD), and a remote, pain-free control area (CON).

Methods

Fifty-nine patients with CLBP (51 years, SD = 16.6, 22 female patients) and 35 pain-free control participants individually matched for age, sex, and testing areas (49 years, SD = 17.5, 19 female participants) underwent a full QST protocol in MP and a reduced QST protocol assessing sensory gain in AD and CON. Quantitative sensory testing measures, except paradoxical heat sensations and dynamic mechanical allodynia (DMA), were Z-transformed to the matched control participants and tested for significance using Z-tests (α = 0.001). Paradoxical heat sensations and DMA occurrence were compared between cohorts using Fisher's exact tests (α = 0.05). The same analyses were performed with a high-pain and a low-pain CLBP subsample (50% quantile).

Results

Patients showed cold and vibration hypoesthesia in MP (all Ps < 0.001) and mechanical hyperalgesia (P < 0.001) and more frequent DMA (P = 0.044) in AD. The results were mainly driven by the high-pain CLBP subsample. In CON, no sensory alterations were observed.

Conclusion

Mechanical hyperalgesia and DMA adjacent to but not within MP, the supposedly primarily affected area, might reflect secondary hyperalgesia originating from spinal sensitization in patients with CLBP.

Sensory phenotypes in complex regional pain syndrome and chronic low back pain-indication of common underlying pathomechanisms

Introduction

First-line pain treatment is unsatisfactory in more than 50% of chronic pain patients, likely because of the heterogeneity of mechanisms underlying pain chronification.

Objectives

This cross-sectional study aimed to better understand pathomechanisms across different chronic pain cohorts, regardless of their diagnoses, by identifying distinct sensory phenotypes through a cluster analysis.

Methods

We recruited 81 chronic pain patients and 63 age-matched and sex-matched healthy controls (HC). Two distinct chronic pain cohorts were recruited, ie, complex regional pain syndrome (N = 20) and low back pain (N = 61). Quantitative sensory testing (QST) was performed in the most painful body area to investigate somatosensory changes related to clinical pain. Furthermore, QST was conducted in a pain-free area to identify remote sensory alterations, indicating more widespread changes in somatosensory processing.

Results

Two clusters were identified based on the QST measures in the painful area, which did not represent the 2 distinct pain diagnoses but contained patients from both cohorts. Cluster 1 showed increased pain sensitivities in the painful and control area, indicating central sensitization as a potential pathomechanism. Cluster 2 showed a similar sensory profile as HC in both tested areas. Hence, either QST was not sensitive enough and more objective measures are needed to detect sensitization within the nociceptive neuraxis or cluster 2 may not have pain primarily because of sensitization, but other factors such as psychosocial ones are involved.

Conclusion

These findings support the notion of shared pathomechanisms irrespective of the pain diagnosis. Conversely, different mechanisms might contribute to the pain of patients with the same diagnosis.

Fibromyalgia patients with elevated levels of anti-satellite glia cell immunoglobulin G antibodies present with more severe symptoms

ABSTRACT

Transferring fibromyalgia patient immunoglobulin G (IgG) to mice induces pain-like behaviour, and fibromyalgia IgG binds mouse and human satellite glia cells (SGCs). These findings suggest that autoantibodies could be part of fibromyalgia pathology. However, it is unknown how frequently fibromyalgia patients have anti-SGC antibodies and how anti-SGC antibodies associate with disease severity. Here, we quantified serum or plasma anti-SGC IgG levels in 2 fibromyalgia cohorts from Sweden and Canada using an indirect immunofluorescence murine cell culture assay. Fibromyalgia serum IgG binding to human SGCs in human dorsal root ganglia tissue sections was also assessed by immunofluorescence. In the cell culture assay, anti-SGC IgG levels were increased in both fibromyalgia cohorts compared with control group. Elevated anti-SGC IgG was associated with higher levels of self-reported pain in both cohorts, and higher fibromyalgia impact questionnaire scores and increased pressure sensitivity in the Swedish cohort. Anti-SGC IgG levels were not associated with fibromyalgia duration. Swedish fibromyalgia (FM) patients were clustered into FM-severe and FM-mild groups, and the FM-severe group had elevated anti-SGC IgG compared with the FM-mild group and control group. Anti-SGC IgG levels detected in culture positively correlated with increased binding to human SGCs. Moreover, the FM-severe group had elevated IgG binding to human SGCs compared with the FM-mild and control groups. These results demonstrate that a subset of fibromyalgia patients have elevated levels of anti-SGC antibodies, and the antibodies are associated with more severe fibromyalgia symptoms. Screening fibromyalgia patients for anti-SGC antibodies could provide a path to personalized treatment options that target autoantibodies and autoantibody production.

The Impact of Micro RNA-320a Serum Level on Severity of Symptoms and Cerebral Processing of Pain in Patients with Fibromyalgia

OBJECTIVES

The aim of this work was to explore the expression of miR-320a level in fibromyalgia patients in comparison to healthy controls, and to clarify its impact on the severity of symptoms and the cerebral processing of pain assessed by middle latency somatosensory evoked potentials (SSEPs).

DESIGN

Case-control study.

SETTING

Rheumatology and Neurology outpatient clinics.

SUBJECTS

Seventy-four fibromyalgia patients and seventy-four normal healthy controls.

METHODS

The included patients were subjected to detailed history taking, assessment of severity of fibromyalgia symptoms using the Fibromyalgia Impact Questionnaire Revised (FIQR), assessment of pain intensity using the Neuropathic Pain Symptom Inventory (NPSI), measurement of the serum level of miR-320a in addition to of measurement peak latencies and amplitudes of middle latency SSEPs.

RESULTS

Fibromyalgia patients had significantly higher micro-RNA-320a levels (0.907 ± 0.022) in comparison to controls (0.874 ± 0.015) (P-value < .001). The mean values of micro-RNA-320a levels were significantly higher in fibromyalgia patients with insomnia, chronic fatigue syndrome, persistent depressive disorder, and primary headache disorder than those without (P-value = .024, <.001, .006, .036 respectively). There were statistically significant positive correlations between micro-RNA-320a levels, and disease duration, FIQR, and NPSI total scores (P-value <0.001, 0.003, 0.002 respectively). There were no statistically significant correlations between micro-RNA-320a levels and middle latency SSEPs.

DISCUSSION

Micro-RNA-320a level is significantly upregulated in fibromyalgia patient. It has a crucial impact on the severity of symptoms but not related to the cerebral processing of pain.

Algometry for the assessment of central sensitisation to pain in fibromyalgia patients: a systematic review

INTRODUCTION

The pathophysiology of fibromyalgia (FM) is related to central sensitisation (CS) to pain. Algometry allows assessing CS based on dynamic evoked pain. However, current algometrýs protocols require optimising, unifying and updating.

OBJECTIVES

1) identify the dynamic pain measures used most frequently to effectively assess CS processes in FM, and 2) consider the future of the algometry assessing CS in these patients.

METHODS

Cochrane Collaboration guidelines and PRISMA statements were followed. The protocol was registered in PROSPERO database (ID: CRD42021270135). The selected articles were evaluated using the Cochrane risk of bias (ROB) assessment tool. The PubMed, Scopus, and Web of Science databases were searched.

RESULTS

Thirty-four studies were selected, including measures such as temporal summation of pain (TSP), aftersensations (AS), spatial summation of pain (SSP), the noxious flexion reflex (NFR) threshold, conditioned pain modulation (CPM), cutaneous silent period (CuSP), and slowly repeated evoked pain (SREP); and evoked pain combined with neuroimaging. Each measure offered various advantages and limitations. According to ROB, 28 studies were of low quality, 3 of moderate quality, and 3 of high quality.

CONCLUSIONS

Several pain indicators have been demonstrated to successfully examine CS involvement in FM in the last years. Algometry, especially when it involves diverse body sites and tissues, might provide further insight into (1) the evaluation of psychological factors known to influence pain experience, (2) new dynamic pain indicators, and (3) the simultaneous use of certain neuroimaging techniques. Further research clarifying the mechanisms underlying some of these measures, and homogenisation and optimisation of the algometrýs protocols, are needed. KEY MESSAGESAlgometry allows for assessing Central Sensitisation by applying dynamic evoked pain.The future of algometry could relapse in its combination with neuroimaging.Recently-emerged pain indicators should be considered for algometrýs new protocols.

Thalamocortical bistable switch as a theoretical model of fibromyalgia pathogenesis inferred from a literature survey

Fibromyalgia (FM) is an unsolved central pain processing disturbance. We aim to provide a unifying model for FM pathogenesis based on a loop network involving thalamocortical regions, i.e., the ventroposterior lateral thalamus (VPL), the somatosensory cortex (SC), and the thalamic reticular nucleus (TRN). The dynamics of the loop have been described by three differential equations having neuron mean firing rates as variables and containing Hill functions to model mutual interactions among the loop elements. A computational analysis conducted with MATLAB has shown a transition from monostability to bistability of the loop behavior for a weakening of GABAergic transmission between TRN and VPL. This involves the appearance of a high-firing-rate steady state, which becomes dominant and is assumed to represent pathogenic pain processing giving rise to chronic pain. Our model is consistent with a bulk of literature evidence, such as neuroimaging and pharmacological data collected on FM patients, and with correlations between FM and immunoendocrine conditions, such as stress, perimenopause, chronic inflammation, obesity, and chronic dizziness. The model suggests that critical targets for FM treatment are to be found among immunoendocrine pathways leading to GABA/glutamate imbalance having an impact on the thalamocortical system.

Long-lasting reflexive and nonreflexive pain responses in two mouse models of fibromyalgia-like condition

Nociplastic pain arises from altered nociception despite no clear evidence of tissue or somatosensory system damage, and fibromyalgia syndrome can be highlighted as a prototype of this chronic pain subtype. Currently, there is a lack of effective treatments to alleviate both reflexive and nonreflexive pain responses associated with fibromyalgia condition, and suitable preclinical models are needed to assess new pharmacological strategies. In this context, although in recent years some remarkable animal models have been developed to mimic the main characteristics of human fibromyalgia, most of them show pain responses in the short term. Considering the chronicity of this condition, the present work aimed to develop two mouse models showing long-lasting reflexive and nonreflexive pain responses after several reserpine (RIM) or intramuscular acid saline solution (ASI) injections. To our knowledge, this is the first study showing that RIM6 and ASI mouse models show reflexive and nonreflexive responses up to 5-6 weeks, accompanied by either astro- or microgliosis in the spinal cord as pivotal physiopathology processes related to such condition development. In addition, acute treatment with pregabalin resulted in reflexive pain response alleviation in both the RIM6 and ASI models. Consequently, both may be considered suitable experimental models of fibromyalgia-like condition, especially RIM6.

Central pain modulatory mechanisms of attentional analgesia are preserved in fibromyalgia

ABSTRACT

Fibromyalgia is a prevalent pain condition that is associated with cognitive impairments including in attention, memory, and executive processing. It has been proposed that fibromyalgia may be caused by altered central pain processing characterised by a loss of endogenous pain modulation. We tested whether attentional analgesia, where cognitive engagement diminishes pain percept, was attenuated in patients with fibromyalgia (n = 20) compared with matched healthy controls (n = 20). An individually calibrated, attentional analgesia paradigm with a 2 × 2 factorial design was used with brain and brainstem-focussed functional magnetic resonance imaging. Patients with fibromyalgia had both lower heat pain thresholds and speeds in a visual attention task. When this was taken into account for both attentional task and thermal stimulation, both groups exhibited an equivalent degree of attentional analgesia. Functional magnetic resonance imaging analysis showed similar patterns of activation in the main effects of pain and attention in the brain and brainstem (with the sole exceptions of increased activation in the control group in the frontopolar cortex and the ipsilateral locus coeruleus). The attentional analgesic effect correlated with activity in the periaqueductal gray and rostral ventromedial medulla. These findings indicate that patients with fibromyalgia can engage the descending pain modulatory system if the attentional task and noxious stimulus intensity are appropriately titrated.

Tactile Detection in Fibromyalgia: A Systematic Review and a Meta-Analysis

Fibromyalgia is a chronic pain syndrome characterized by sensorimotor deficits and distortions of body representation, that could both be caused by alterations in sensory processing. Several studies suggest a hypersensitivity to various sensory stimulations in fibromyalgia but results on detection of both noxious and non-noxious tactile stimulation, which are particularly relevant for body representation and motor control, remain conflicting. Therefore, the aim of this study is to systematically review and quantify the detection thresholds to noxious and non-noxious tactile stimuli in individuals with fibromyalgia compared to pain-free controls. A systematic review and a meta-analysis were performed in the MEDLINE, EMBASE, CINAHL, Cochrane, PsycInfo and Web of Science databases using keywords related to fibromyalgia, tactile pain detection threshold, tactile detection threshold and quantitative sensory testing. Nineteen studies were included in the review, with 12 in the meta-analysis. Despite the heterogeneity of the results, the data from both the review and from the meta-analysis suggest a trend toward hyperalgesia and no difference of sensitivity to non-noxious tactile stimuli in participants with fibromyalgia compared to healthy controls. This contradicts the hypothesis of a general increase in responsiveness of the central nervous system to noxious and non-noxious stimulations in fibromyalgia. This study shows no alteration of the sensitivity to non-noxious tactile stimulation in fibromyalgia, suggesting that an altered unimodal processing is not sufficient to explain symptoms such as sensorimotor impairments and body representation distortions. Future research should investigate whether alterations in multisensory integration could contribute to these symptoms.

Thermal Pain Thresholds Are Significantly Associated with Plasma Proteins of the Immune System in Chronic Widespread Pain-An Exploratory Pilot Study Using Multivariate and Network Analyses

Chronic widespread pain (CWP), including fibromyalgia (FM), is characterized by generalized musculoskeletal pain. An important clinical feature is widespread increased pain sensitivity such as lowered pain thresholds for different stimuli such as heat (HPT) and cold (CPT). There is a growing interest in investigating the activated neurobiological mechanisms in CWP. This explorative proteomic study investigates the multivariate correlation pattern between plasma and muscle proteins and thermal pain thresholds in CWP and in healthy controls (CON). In addition, we analysed whether the important proteins and their networks for CPT and HPT differed between CWP and CON. We used a proteomic approach and analysed plasma and muscle proteins from women with CWP (n = 15) and CON (n = 23). The associations between the proteins and CPT/HPT were analysed using orthogonal partial least square (OPLS). The protein-protein association networks for the important proteins for the two thermal pain thresholds were analysed using STRING database. CWP had lowered pain thresholds for thermal stimulus. These levels were generally not related to the included clinical variables except in CWP for HPT. Highly interacting proteins mainly from plasma showed strong significant associations with CPT and HPT both in CWP and in CON. Marked differences in the important proteins for the two thermal pain thresholds were noted between CWP and CON; more complex patterns emerged in CWP. The important proteins were part of the immune system (acute phase proteins, complement factors, and immunoglobulin factors) or known to interact with the immune system. As expected, CWP had lowered pain thresholds for thermal stimulus. Although different proteins were important in the two groups, there were similarities. For example, proteins related to the host defence/immunity such as acute phase proteins, complement factors, immunoglobulin factors, and cytokines/chemokines (although not in CON for CPT) were important habitual/tonic factors for thermal pain thresholds. The fact that peripheral proteins contribute to thermal pain thresholds does not exclude that central factors also contribute and that complex interactions between peripheral and central factors determine the registered pain thresholds in CWP.

Fibromyalgia Patients Are Not Only Hypersensitive to Painful Stimuli But Also to Acoustic Stimuli

Fibromyalgia is a chronic widespread pain syndrome associated with hypersensitivity to nociceptive stimuli. This increased sensitivity of FM patients has been associated with central sensitization of dorsal horn neurons. Increasing evidence, however, suggests that the mechanisms of FM hypersensitivity not only affect pain but include light, smell, and sound. We hypothesized that supraspinal augmentation of sensory input including sound represent a hallmark of FM. We tested 23 FM patients and 28 healthy controls (HC) for sensory augmentation of nociceptive and non-nociceptive sensations: For assessment of nociceptive augmentation we used sensitivity adjusted mechanical and heat ramp & hold stimuli and for assessment of sound augmentation, we applied wideband noise stimuli using a random-staircase design. Quantitative sensory testing demonstrated increased heat and mechanical pain sensitivity in FM participants (P < .001). The sound pressures needed to report mild, moderate, and intense sound levels were significantly lower in FM compared to HC (P < .001), consistent with auditory augmentation. FM patients are not only augmenting noxious sensations but also sound, suggesting that FM augmentation mechanisms are not only operant in the spinal cord but also in the brain. Whether the central nervous system mechanisms for auditory and nociceptive augmentation are similar, needs to be determined in future studies. PERSPECTIVE: This study presents QST evidence that the hypersensitivity of FM patients is not limited to painful stimuli but also to innocuous stimuli like sound. Our results suggest that abnormal brain mechanisms may be responsible for the increased sensitivity of FM patients.

Passive transfer of fibromyalgia symptoms from patients to mice

Fibromyalgia syndrome (FMS) is characterized by widespread pain and tenderness, and patients typically experience fatigue and emotional distress. The etiology and pathophysiology of fibromyalgia are not fully explained and there are no effective drug treatments. Here we show that IgG from FMS patients produced sensory hypersensitivity by sensitizing nociceptive neurons. Mice treated with IgG from FMS patients displayed increased sensitivity to noxious mechanical and cold stimulation, and nociceptive fibers in skin-nerve preparations from mice treated with FMS IgG displayed an increased responsiveness to cold and mechanical stimulation. These mice also displayed reduced locomotor activity, reduced paw grip strength, and a loss of intraepidermal innervation. In contrast, transfer of IgG-depleted serum from FMS patients or IgG from healthy control subjects had no effect. Patient IgG did not activate naive sensory neurons directly. IgG from FMS patients labeled satellite glial cells and neurons in vivo and in vitro, as well as myelinated fiber tracts and a small number of macrophages and endothelial cells in mouse dorsal root ganglia (DRG), but no cells in the spinal cord. Furthermore, FMS IgG bound to human DRG. Our results demonstrate that IgG from FMS patients produces painful sensory hypersensitivities by sensitizing peripheral nociceptive afferents and suggest that therapies reducing patient IgG titers may be effective for fibromyalgia.

Unusual Pain Disorders - What Can Be Learned from Them?

Pain is common in many different disorders and leads to a significant reduction in quality of life in the affected patients. Current treatment options are limited and often result in insufficient pain relief, partly due to the incomplete understanding of the underlying pathophysiological mechanisms. The identification of these pathomechanisms is therefore a central object of current research. There are also a number of rare pain diseases, that are generally little known and often undiagnosed, but whose correct diagnosis and examination can help to improve the management of pain disorders in general. In some of these unusual pain disorders like sodium-channelopathies or sensory modulation disorder the underlying pathophysiological mechanisms have only recently been unravelled. These mechanisms might serve as pharmacological targets that may also play a role in subgroups of other, more common pain diseases. In other unusual pain disorders, the identification of pathomechanisms has already led to the development of new drugs. A completely new therapeutic approach, the gene silencing, can even stop progression in hereditary transthyretin amyloidosis and porphyria, ie in pain diseases that would otherwise be rapidly fatal if left untreated. Thus, pain therapists and researchers should be aware of these rare and unusual pain disorders as they offer the unique opportunity to study mechanisms, identify new druggable targets and finally because early diagnosis might save many patient lives.

Pain matters for central sensitization: sensory and psychological parameters in patients with fibromyalgia syndrome

Sensory abnormalities through quantitative sensory testing in fibromyalgia were not substantially influenced by psychological comorbidities. A significant subgroup showed signs of central sensitization, influenced by pain intensity.

Introduction:

Patients suffering from fibromyalgia syndrome (FMS) are heterogenous. They often present with sensory abnormalities and comorbidities.

Objectives:

We aimed to answer the following questions: (1) Is there a specific somatosensory profile in our patient cohort? (2) Can we detect subgroups characterized by a specific combination of sensory and psychological features? and (3) Do psychological parameters influence sensory signs?

Methods:

In 87 patients with FMS quantitative sensory testing was performed on the hand and evaluated in combination with questionnaire results regarding pain, psychological comorbidities, sleep, and functionality.

Results:

Patients presented different somatosensory patterns, but no specific subgroups regarding sensory signs and psychological features were detected. Hypersensitivity for noxious mechanical and thermal stimuli and hyposensitivity for nonnoxious mechanical stimuli were the most prominent features. Thirty-one percent of patients showed signs of central sensitization as indicated by abnormally increased pinprick hyperalgesia or dynamic mechanical allodynia. Central sensitization was associated with higher pain intensities (P < 0.001). Only a small influence of psychiatric comorbidities on mechanical pain sensitivity (P = 0.044) and vibration detection (P = 0.028) was found, which was partly associated with high pain intensities. A small subgroup of patients (11.4%) demonstrated thermal hyposensitivity (loss of small-fiber function).

Conclusion:

Patients with FMS showed various somatosensory abnormalities. These were not significantly influenced by psychological comorbidities. Signs for central sensitization were detected in about one-third of patients and associated with higher pain intensities. This supports the notion of central sensitization being a major pathophysiological mechanism in FMS, whereas small-fiber loss may be less important.

A Systematic Review Into the Influence of Temperature on Fibromyalgia Pain: Meteorological Studies and Quantitative Sensory Testing

Fibromyalgia syndrome (FMS) is a chronic widespread pain condition of unknown aetiology. The role of temperature in FMS pain has not been reviewed systematically. The goal of this study was to review the influences of temperature on pain in FMS, from meteorological and quantitative sensory testing (QST) studies. The review was registered with Prospero: ID-CRD42020167687, and followed PRISMA guidance. Databases interrogated were: MEDLINE (via OVID), EMBASE, PubMed, Web of Science, ScienceDirect, CINAHL, and ProQuest (Feb'20). Exclusion criteria were: age <18, animal studies, non-English, and noncontrolled articles. Thirteen studies pertaining to ambient temperature and FMS pain were identified; 9 of these found no uniform relationship. Thirty-five QST studies were identified, 17 of which assessed cold pain thresholds (CPTs). All studies showed numerically reduced CPTs in patients, ranging from 10.9°C to 26.3°C versus 5.9°C to 13.5°C in controls; this was statistically significant in 14/17. Other thermal thresholds were often abnormal. We conclude that the literature provides consistent evidence for an abnormal sensitization of FMS patients' temperature-sensation systems. Additional work is required to elucidate the factors that determine why a subgroup of patients perceive low ambient temperatures as painful, and to characterize that group. PERSPECTIVE: Patients often report increased pain with changes in ambient temperature; even disabling, extreme temperature sensitivity in winter. Understanding this phenomenon may help clinicians provide reassurance and advice to patients and may guide research into the everyday impact of such hypersensitivity, whilst directing future work into the pathophysiology of FMS.

Assessing our approach to diagnosing Fibromyalgia

Introduction: Fibromyalgia represents the most prevalent of the group of conditions that are known as central sensitivity syndromes. Approximately 2-5% of the adult population in the United States is affected by Fibromyalgia. This pain amplification syndrome has an enormous economic impact as measured by work absenteeism, decreased work productivity, disability and injury compensation, and over-utilization of healthcare resources. Multiple studies have shown that early diagnosis of this condition can improve patient outlook, and redirect valuable health care resources toward more appropriate targeted therapy. Efforts have been made toward improving diagnostic accuracy through updated criteria. Areas Covered: Reviewed here are 1) reasons for the need for more accurate diagnosis of Fibromyalgia, (2) a review of the evolution of Fibromyalgia to current times, and (3) the proliferation of currently available diagnostic criteria and problems related to each of them. From initial literature review until October 2020, PubMed, Embase, and Scopus were searched for applicable literature. Expert Opinion: A discussion of ongoing efforts to obtain a biomarker to enhance diagnostic accuracy concludes this review. A need to include rheumatologists as part of the care team of patients with Fibromyalgia is emphasized.

Somatosensory profiles in patients with non-specific neck-arm pain with and without positive neurodynamic tests

Despite normal neurological integrity tests, some patients with non-specific neck-arm pain (NSNAP) have heightened nerve mechanosensitivity upon neurodynamic testing. The aim of this study was to determine whether or not a nerve dysfunction is present in patients with positive neurodynamic tests compared to those with negative neurodynamic tests or healthy controls. Somatosensory profiling using quantitative sensory testing (QST) was established in 40 consecutive patients with unilateral NSNAP; 23 had positive upper limb neurodynamic tests (ULNT_POS) and 17 had negative neurodynamic tests (ULNT_NEG) and in 26 healthy controls. QST included measurement of thermal and mechanical detection and pain thresholds in the maximal pain area on the symptomatic side as well as the corresponding contralateral area. Fifty-seven percent of patients with NSNAP had positive neurodynamic tests. Somatosensory profiling revealed a loss of function phenotype in NSNAP patients compared to healthy controls both in the maximal pain area and asymptomatic side. Hyperalgesia (cold, heat and pressure) was present bilaterally in both NSNAP groups. Direct comparison between the patient groups revealed no significant differences in somatosensory profiles. However, the ULNT_POS group demonstrated sensory loss compared to healthy controls in more parameters than the ULNT_NEG group. The ULNT_NEG subgroup represented an intermediate phenotype between ULNT_POS patients and healthy controls in most detection thresholds as well as thermal and pressure pain thresholds. Even though patients with NSNAP present as a spectrum, it remains unclear whether the sensory changes are indicative of a nerve dysfunction/lesion or rather a marker of altered central pain processing.

Reliability and Validity of the Boston Bedside Quantitative Sensory Testing Battery for Neuropathic Pain

OBJECTIVE

Recent studies suggest that sensory phenotyping may provide critical information for the diagnosis and management of patients with chronic neuropathic pain (NP). However, many formal quantitative sensory testing (QST) paradigms require expensive equipment, a dedicated location, and substantial time commitments on the part of patient and examiner, highlighting the need for a convenient and portable "bedside" QST battery. We developed and tested a bedside QST battery in a sample of patients with chronic NP.

METHODS

Participants (N = 51) attended two in-person visits over approximately two weeks, during which they underwent QST using both laboratory-based equipment and simple, easily accessible bedside tools. Participants also completed questionnaires about their daily pain and NP symptoms.

RESULTS

Test-retest reliability estimates were highly statistically significant and did not differ between bedside (mean r = 0.60) and laboratory-based (mean r = 0.72) QST. Bedside QST variables and corresponding laboratory-based QST variables were highly correlated, suggesting adequate criterion validity for the bedside tests.

CONCLUSIONS

Results from the present study may have important implications for the sensory phenotyping and subsequent management of patients with chronic NP. Implementation of a protocol that uses inexpensive, portable, and convenient tools may allow for the application of QST in variety of clinical settings and advance NP research.

Conditioned pain modulation in elite athletes: a systematic review and meta-analysis

Background and aims Elite athletes reportedly have superior pain tolerances, but it is unclear if results extend to conditioned pain modulation (CPM). The aim of our study was to synthesize existing literature in order to determine whether CPM is increased in elite athletes compared to healthy controls. Methods A systematic review and random-effects meta-analysis was conducted. Cochrane Central Register of Controlled Trials, SPORTDiscus, PsycINFO, CINAHL, Web of Science, and PubMed were searched for English-language studies that examined CPM in adult elite athlete populations. Results Seven studies were identified; all were of poor to fair methodological quality. There was no overall difference in CPM between elite athletes and controls (Hedges g = 0.37, CI95 -0.03-0.76; p = 0.07). There was heterogeneity between studies, including one that reported significantly less CPM in elite athletes compared to controls. An exploratory meta-regression indicated that a greater number of hours trained per week was associated with higher CPM. Conclusions The overall number and quality of studies was low. Despite nominally favoring higher CPM in elite athletes, aggregate results indicate no significant difference compared to healthy controls. A possible factor explaining the high degree of variability between studies is the number of hours elite athletes spent training. Implications Based on available evidence, athletes do not have remarkable endogenous pain modulation compared to controls. High quality experimental studies are needed to address the effect of hours trained per week on CPM in athletes.

Automated Nociceptive Withdrawal Reflex Measurements Reveal Normal Reflex Thresholds and Augmented Pain Ratings in Patients with Fibromyalgia

The nociceptive withdrawal reflex (NWR) is used to probe spinal cord excitability in chronic pain states. Here, we used an automated and unbiased procedure for determining the NWR threshold and compared the reflex thresholds and corresponding pain ratings in a well-characterized cohort of fibromyalgia (n = 29) and matched healthy controls (n = 21). Surface electrical stimuli were delivered to the foot in a stepwise incremental and decremental manner. The surface electromyographic activity was recorded from the ipsilateral tibialis anterior muscle. Fibromyalgia patients reported significantly higher scores for psychological distress and pain-related disability and a significantly lower score for perceived state of health compared to the matched controls. The subjective pain ratings were significantly higher in patients. The NWR thresholds were similar to the controls. In the patients, but not in controls, the NWR thresholds and subjective pain ratings were significantly correlated. Our results showed an increased subjective pain sensitivity in fibromyalgia, but we found no evidence for spinal sensitization based on the reflex measures.

Anhedonia to Gentle Touch in Fibromyalgia: Normal Sensory Processing but Abnormal Evaluation

Social touch is important for interpersonal interaction. Gentle touch and slow brushing are typically perceived as pleasant, the degree of pleasantness is linked to the activity of the C-tactile (CT) fibers, a class of unmyelinated nerves in the skin. The inability to experience pleasure in general is called anhedonia, a common phenomenon in the chronic pain condition fibromyalgia. Here, we studied the perception and cortical processing of gentle touch in a well-characterized cohort of fibromyalgia. Patients and controls participated in functional brain imaging while receiving tactile stimuli (brushing) on the forearm. They were asked to provide ratings of pleasantness of the tactile stimulus and ongoing pain. We found high distress, pain catastrophizing, and insomnia, and a low perceived state of health in fibromyalgia. Further, patients rated both slow (CT-optimal) and fast (CT-suboptimal) brushing as less pleasant than healthy participants. While there was no difference in brain activity during touch, patients showed deactivation in the right posterior insula (contralateral to the stimulated arm) during pleasantness rating and activation during pain rating. The opposite pattern was observed in healthy participants. Voxel-based morphometry analysis revealed reduced grey matter density in patients, in the bilateral hippocampus and anterior insula. Our results suggest anhedonia to gentle touch in fibromyalgia with intact early-stage sensory processing but dysfunctional evaluative processing. These findings contribute to our understanding of the mechanisms underlying anhedonia in fibromyalgia.

Small fibre pathology in chronic whiplash-associated disorder: A cross-sectional study

BACKGROUND

Mechanisms underpinning ongoing symptoms in chronic whiplash associated-disorder (WAD) are not well understood. People with chronic WAD can exhibit sensory dysfunction consistent with small nerve fibre pathology, including thermal hypoaesthesia and hyperalgesia. This study investigated small fibre structure and function in chronic WAD.

METHODS

Twenty-four people with chronic WAD (median [IQR] age 49 [15] years, 16 females) and 24 pain-free controls (50 [17] years, 16 females) were recruited. Intraepidermal nerve fibre density (IENFD) and dermal innervation were assessed by skin biopsy. This was performed at (a) the lateral index finger on the primary side of pain and (b) superior to the lateral malleolus on the contralateral side. Quantitative sensory testing was performed over the hand.

RESULTS

The WAD group exhibited lower IENFD at the finger (WAD: median [IQR] 4.5 [4.9] fibres/mm; control 7.3 [3.9]; p = .010), but not the ankle (WAD: mean [SD] 7.3 [3.7] fibres/mm; control 9.3 [3.8]; p = .09). Dermal innervation was lower in the WAD group at the finger (WAD: median [IQR] 3.7 [2.8] nerve bundles/mm² ; controls: 4.9 [2.1]; p = .017) but not the ankle (WAD: median [IQR] 2.1 [1.9] nerve bundles/mm² ; controls: 1.8 [1.8]; p = .70). In the WAD group, hand thermal and light touch detection were impaired, and heat pain thresholds were lowered (p ≤ .037).

CONCLUSIONS

Findings suggest small fibre structural and functional deficits in chronic WAD, implicating potential involvement of small fibre pathology.

SIGNIFICANCE

Our study found decreased intraepidermal nerve fibre density, reduced dermal innervation, thermal hypoaesthesia and hypersensitivity in people with chronic WAD, suggestive of small fibre pathology. This observation of peripheral nervous system pathology in chronic whiplash provides novel insights on mechanisms underpinning symptoms and challenges commonly held beliefs regarding this condition.

Quantitative Sensory Testing in Patients with Multisomatoform Disorder with Chronic Pain as the Leading Bodily Symptom-a Matched Case-Control Study

OBJECTIVE

Chronic pain is a debilitating condition of multifactorial origin, often without physical findings to explain the presenting symptoms. Of the possible etiologies of persisting painful symptoms, somatoform disorders and functional somatic syndromes (FSS) are among the most challenging, with a prevalence of 8-20%. Many different somatoform disorders and FSS have overlapping symptoms, with pain being the most prevalent one. The concept of multisomatoform disorder (MSD) has been developed to acknowledge that fact. We hypothesized that the concept of MSD will be reflected in a distinct sensory profile of patients compared with healthy controls and possibly provide insight into the type and pathophysiology of the pain commonly experienced by patients.

DESIGN

We performed comprehensive quantitative sensory testing (QST) in 151 patients and 149 matched controls.

RESULTS

There were significant differences in the sensory profiles of patients compared with controls. Patients with MSD showed a combination of tactile and thermal hypesthesia combined with mechanical and cold hyperalgesia. This was true for measurements at test and control sites, with the exception of vibration detection threshold and mechanical pain threshold. Among the observed changes, a marked sensory loss of function, as evidenced by an increase in cold detection threshold, and a marked gain of function, as evidenced by a decrease of pressure pain threshold, were most notable. There was no evidence of concurrent medication influencing QST results.

CONCLUSIONS

The observed somatosensory profile of patients with MSD resembles that of patients suffering from neuropathic pain with evidence of central sensitization.

Clinical characteristics of neuropathic pain in leprosy and associated somatosensory profiles: a deep phenotyping study in India

This study investigated the clinical characteristics and somatosensory profiles of patients suffering from leprosy in Mumbai, India. A cross-sectional deep profiling study was conducted in 86 patients with leprosy (with and without pain) using an extensive battery of phenotyping measures including structured clinical examination, psychological state (General Health Questionnaire [GHQ-12]), and a quality-of-life condition-specific instrument (Brief Pain Inventory-short form). Quantitative sensory testing was performed according to the protocol of the German Research Network on Neuropathic Pain (DFNS) to assess the somatosensory profiles in the ulnar nerve innervation territory of all participants (dorsum of the hand). Reference data from 50 healthy Indian subjects were within the range of published DFNS values. Somatosensory profiles in leprosy patients with clinically or electroneurographically diagnosed neuropathy (with and without pain) revealed a profile of sensory loss to thermal and tactile stimuli combined with preservation of vibration and deep pressure detection. Sensory gain phenomena were not generally observed in patients with leprosy. In the group of subclinical neuropathy, a high degree of impaired thermal sensation was found, which could be clinically deployed to enhance identification of leprosy neuropathy at an early stage. Quantitative sensory testing can effectively document leprosy-associated neuropathy but does not distinguish between patients with or without pain. Patients with leprosy and neuropathic pain reported a poor quality of life and less psychological well-being compared with the pain-free patients with leprosy neuropathy.

Quantitative sensory testing to evaluate and compare the results after epidural injection and simple discectomy, in patients with radiculopathy secondary to lumbar disc herniation

The objective assessment of the radiculopathy secondary to lumbar disc herniation is essential to optimize treatment. The quantitative sensory test (QST) is a useful tool to evaluate somatosensory nerves. The aim of our study is quantifying by QST the alterations of patients treated by epidural injections (EI) or surgical lumbar decompression (LD). A prospective, cohort study has done in Hospital Universitario Rio Hortega, Valladolid, Spain, between January 2014 and December 2016.The study includes 74 patients (40 men) who underwent EI (50) or LD (24) with lumbar disc herniation and treated by EI or LD. Participants underwent a brief battery of QST at baseline and after 1, 3 and 6 months of follow-up. QST threshold were measured in three series of five warm and cold stimuli (cold detection threshold, warm detection threshold, cold pain threshold, heat pain threshold) bilateral. Additionally, pain assessment (Visual Analogue Scale) and neurological examination was performed. Thermal thresholds were analysed and compared. In the EI group, warm detection threshold (WDT) measurements were significantly lower after 3 and 6 months of follow-up (40.44 ± 3.42°C vs. 38.30 ± 3.73°C and 37.48 ± 4.58°C respectively, p = 0.031 and p = 0.043). LD group showed lower WDT measurements at 1, 3 and 6 months of follow up (40.20 ± 2.97°C vs., 37.98 ± 2.04°C, 37.43 ± 3.80°C and 36.55 ± 2.77°C respectively, p = 0.049, p = 0.032 and p = 0.024) and lower heat pain threshold (HPT) levels after 3 and 6 months of follow-up (48.75 ± 1.37°C vs. 43.26 ± 0.60°C and 42.06 ± 1.37°C respectively, p = 0.037 and p = 0.021). QST explorations were compared between both groups. At 1-month follow-up only the WDT parameter was different, higher in EI group (40.98 ± 4.04°C vs. 37.98 ± 2.04°C, p = 0.043). There were no differences in any parameter measured by QST after 3 and 6-months follow-up between both groups. Epidural injection should be considered the first-step of treatment.

Thermal and Mechanical Pain Thresholds of Women With Provoked Localized Vulvodynia: A Pilot Study

Context

Vulvodynia is a chronic pain condition defined as vulvar pain lasting at least 3 months in the absence of gross anatomic or neurologic findings. Provoked, localized vulvodynia (PLV), a subtype of vulvodynia, is characterized by vestibular pain in response to light touch. The cause of PLV remains largely unknown, and triggering events have yet to be determined.

Objective

To evaluate vestibular and peripheral experimental pain thresholds in patients with PLV to further define the somatosensory profile of these patients.

Methods

After informed consent was provided, eligible participants completed a questionnaire and underwent quantitative sensory testing at the forearm and posterior vestibule. Detection and pain thresholds to thermal (cold and heat) and mechanical (pressure) stimuli were measured.

Results

Seventeen participants with PLV and 16 control participants were included. Participants in the PLV group scored lower on the patient health questionnaire 9 (PHQ-9) compared with those in the control group (P<.05) and had higher ratings of self-reported genital pain with sex (P<.001) and daily activity (P<.05). Forearm pain thresholds to cold (P<.01) and heat (P<.01) stimuli were also lower in the PLV group compared with those in the control group. Vestibular pain thresholds to cold (P<.05) and pressure (P<.01) stimuli were also lower in the PLV group.

Conclusion

Lower scores on the PHQ-9 and higher self-reported genital pain ratings of patients with PLV highlight the significant impact of this poorly understood condition on quality of life. Quantitative sensory testing results demonstrated that vestibular cold allodynia may be a somatosensory feature of PLV. Reduced forearm pain thresholds in these patients suggest altered sensory processing at extrapelvic sites, although it is unclear whether these measurements are related to central sensitization.

Development and preliminary evaluation of a short self-report measure of generalized pain hypersensitivity

Purpose

Generalized pain hypersensitivity is frequently observed in chronic pain conditions. Currently, identification is based on expert clinical opinion, and in very few cases combined with quantitative sensory testing. The objectives of this study were to develop and evaluate a short self-report measure of generalized pain hypersensitivity: a generalized pain questionnaire (GPQ).

Methods

Items for the GPQ were developed based on a literature review, followed by an interview study with ten rheumatic patients with suspected pain hypersensitivity. We examined the psychometric properties of the preliminary items in a sample of 212 outpatients suffering from either fibromyalgia (FM; n=98) or rheumatoid arthritis (n=114). Additionally, self-reported data were gathered on sociodemographics, fibromyalgia-survey criteria, health status, and neuropathic-like pain features.

Results

Mokken-scale analyses demonstrated a unidimensional seven-item scale with strong homogeneity (H=0.65) and high reliability (r=0.90). Correlations between total GPQ scores and relevant external measures, such as the FM-survey criteria and neuropathic-like pain features, were consistent with a priori expectations, supporting its external construct validity. Furthermore, the GPQ had good accuracy in distinguishing between patients with FM (generally assumed to be the result of central nervous system hypersensitization) and patients with RA (assumed to result mostly in local nociceptive or inflammatory pain), with an area under the receiver-operating characteristic curve of 0.89. A cutoff value >10 had the highest combination of sensitivity (82.7%) and specificity (77.2%).

Conclusion

The GPQ is psychometrically sound and appears promising for measuring the presence and severity of generalized pain hypersensitivity in chronic pain patients.

Potency of descending pain modulatory system is linked with peripheral sensory dysfunction in fibromyalgia: An exploratory study

Fibromyalgia (FM) is characterized by chronic widespread pain whose pathophysiological mechanism is related to central and peripheral nervous system dysfunction. Neuropathy of small nerve fibers has been implicated due to related pain descriptors, psychophysical pain, and neurophysiological testing, as well as skin biopsy studies. Nevertheless, this alteration alone has not been previously associated to the dysfunction in the descending pain modulatory system (DPMS) that is observed in FM. We hypothesize that they associated, thus, we conducted a cross-sectional exploratory study.To explore small fiber dysfunction using quantitative sensory testing (QST) is associated with the DPMS and other surrogates of nociceptive pathways alterations in FM.We run a cross-sectional study and recruited 41 women with FM, and 28 healthy female volunteers. We used the QST to measure the thermal heat threshold (HTT), heat pain threshold (HPT), heat pain tolerance (HPT), heat pain tolerance (HPTo), and conditional pain modulation task (CPM-task). Algometry was used to determine the pain pressure threshold (PPT). Scales to assess catastrophizing, anxiety, depression, and sleep disturbances were also applied. Serum brain-derived neurotrophic factor (BDNF) was measured as a marker of neuroplasticity. We run multivariate linear regression models by group to study their relationships.Samples differed in their psychophysical profile, where FM presented lower sensitivity and pain thresholds. In FM but not in the healthy subjects, regression models revealed that serum BDNF was related to HTT and CPM-Task (Hotelling Trace = 1.80, P < .001, power = 0.94, R = 0.64). HTT was directly related to CPM-Task (B = 0.98, P = .004, partial-η = 0.25), and to HPT (B = 1.61, P = .008, partial η = 0.21), but not to PPT. Meanwhile, BDNF relationship to CPM-Task was inverse (B = -0.04, P = .043, partial-η = 0.12), and to HPT was direct (B = -0.08, P = .03, partial-η = 0.14).These findings high spot that in FM the disinhibition of the DPMS is positively correlated with the dysfunction in peripheral sensory neurons assessed by QST and conversely with serum BDNF.

Chronic pain patients can be classified into four groups: Clustering-based discriminant analysis of psychometric data from 4665 patients referred to a multidisciplinary pain centre (a SQRP study)

OBJECTIVE

To subgroup chronic pain patients using psychometric data and regress the variables most responsible for subgroup discrimination.

DESIGN

Cross-sectional, registry-based study.

SETTING AND SUBJECTS

Chronic pain patients assessed at a multidisciplinary pain centre between 2008 and 2015.

METHODS

Data from the Swedish quality registry for pain rehabilitation (SQRP) were retrieved and analysed by principal component analysis, hierarchical clustering analysis, and partial least squares-discriminant analysis.

RESULTS

Four subgroups were identified. Group 1 was characterized by low "psychological strain", the best relative situation concerning pain characteristics (intensity and spreading), the lowest frequency of fibromyalgia, as well as by a slightly older age. Group 2 was characterized by high "psychological strain" and by the most negative situation with respect to pain characteristics (intensity and spreading). Group 3 was characterized by high "social distress", the longest pain durations, and a statistically higher frequency of females. The frequency of three neuropathic pain conditions was generally lower in this group. Group 4 was characterized by high psychological strain, low "social distress", and high pain intensity.

CONCLUSIONS

The identification of these four clusters of chronic pain patients could be useful for the development of personalized rehabilitation programs. For example, the identification of a subgroup characterized mainly by high perceived "social distress" raises the question of how to best design interventions for such patients. Differentiating between clinically important subgroups and comparing how these subgroups respond to interventions is arguably an important area for further research.

Pain and Fatigue Variability Patterns Distinguish Subgroups of Fibromyalgia Patients

The current study examined between- and within-subject variability in pain-related symptoms as predictors of pain and fatigue, and identified patient subgroups on the basis of symptom variability characteristics. Two hundred fifty-six fibromyalgia (FM) patients completed daily diaries up to a period of 154 days and reported on symptoms of pain intensity, pain unpleasantness, fatigue, anxiety, and depressed mood. Measures of health status, quality of life, and somatic symptoms were obtained at baseline, and hierarchical linear modeling and cluster analyses were used. Significant intra- and interindividual variability in daily FM symptoms was observed. Higher levels of pain were associated with greater fluctuations in pain unpleasantness, fatigue, and depressed mood. Similar effects were observed for fatigue and individual variability in anxiety also emerged as a robust predictor. Three FM subgroups were revealed: low variability in symptoms (cluster 1), high symptom variability (cluster 2), and a mixed variability group characterized by low fluctuation in pain unpleasantness; moderate pain, fatigue, and depressed mood variability; and high anxiety variability (cluster 3). Cluster 3 exhibited lower social functioning and higher levels of pain, compared with cluster 1. These findings support the dynamic nature of FM pain and suggest the presence of FM subgroups on the basis of variation in mood and pain symptomatology.

PERSPECTIVE

FM patients show significant intra- and interindividual variability in pain, mood, and fatigue. Subgroups in mood and pain-related variability emerged, with phenotypic clusters differing across levels of pain intensity and social functioning. Better understanding of the processes affecting pain variability may facilitate targeted treatments for the control of pain.

Somatic symptom presentations in women with fibromyalgia are differentially associated with elevated depression and anxiety

This study examined whether depression and anxiety differentially relate to fatigue, sleep disturbance, pain catastrophizing, fear of movement, and pain severity in women with fibromyalgia. Baseline data from the Fibromyalgia Activity Study with Transcutaneous Electrical Nerve Stimulation were analyzed. Of 191 participants, 50 percent reported high anxiety and/or depression (17% high anxiety, 9% high depression, and 24% both). Fatigue and sleep impairment were associated with high depression (p < 0.05). Pain severity, pain catastrophizing, and fear of movement were associated with high anxiety and high depression (p < 0.05). Possible implications for underlying mechanisms and the need for targeted treatments are discussed.

Central sensitization associated with low fetal hemoglobin levels in adults with sickle cell anemia

BACKGROUND AND AIMS

Pain is the hallmark of sickle cell anemia (SCA), presenting as recurrent acute events or chronic pain. Central sensitization, or enhanced excitability of the central nervous system, alters pain processing and contributes to the maintenance of chronic pain. Individuals with SCA demonstrate enhanced sensitivity to painful stimuli however central mechanisms of pain have not been fully explored. We hypothesized that adults with SCA would show evidence of central sensitization as observed in other diseases of chronic pain.

METHODS

We conducted a prospective study of static and dynamic quantitative sensory tests in 30 adults with SCA and 30 matched controls.

RESULTS

Static thermal testing using cold stimuli showed lower pain thresholds (p=0.04) and tolerance (p=0.04) in sickle cell subjects, but not for heat. However, SCA subjects reported higher pain ratings with random heat pulses (p<0.0001) and change in scores with temporal summation at the heat pain threshold (p=0.002). Similarly, with the use of pressure pain stimuli, sickle cell subjects reported higher pain ratings (p=0.04), but not higher pressure pain tolerance/thresholds or allodynia to light tactile stimuli. Temporal summation pain score changes using 2 pinprick probes (256 and 512mN) were significantly greater (p=0.004 and p=0.008) with sickle cell, and delayed recovery was associated with lower fetal hemoglobin (p=0.002 and 0.003).

CONCLUSIONS

Exaggerated temporal summation responses provide evidence of central sensitization in SCA.

IMPLICATIONS

The association with fetal hemoglobin suggests this known SCA modifier may have a therapeutic role in modulating central sensitization.

The Potential Role of Sensory Testing, Skin Biopsy, and Functional Brain Imaging as Biomarkers in Chronic Pain Clinical Trials: IMMPACT Considerations

Valid and reliable biomarkers can play an important role in clinical trials as indicators of biological or pathogenic processes or as a signal of treatment response. Currently, there are no biomarkers for pain qualified by the U.S. Food and Drug Administration or the European Medicines Agency for use in clinical trials. This article summarizes an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials meeting in which 3 potential biomarkers were discussed for use in the development of analgesic treatments: 1) sensory testing, 2) skin punch biopsy, and 3) brain imaging. The empirical evidence supporting the use of these tests is described within the context of the 4 categories of biomarkers: 1) diagnostic, 2) prognostic, 3) predictive, and 4) pharmacodynamic. Although sensory testing, skin punch biopsy, and brain imaging are promising tools for pain in clinical trials, additional evidence is needed to further support and standardize these tests for use as biomarkers in pain clinical trials.

PERSPECTIVE

The applicability of sensory testing, skin biopsy, and brain imaging as diagnostic, prognostic, predictive, and pharmacodynamic biomarkers for use in analgesic treatment trials is considered. Evidence in support of their use and outlining problems is presented, as well as a call for further standardization and demonstrations of validity and reliability.

Altered somatosensory profile according to quantitative sensory testing in patients with degenerative lumbar spine disorders scheduled for surgery

Background

Somatosensory profiling in affected and non-affected body regions can strengthen our insight regarding the underlying pain mechanisms, which can be valuable in treatment decision making and to improve outcomes, in patients with degenerative lumbar spine disorders pre-surgery. The aim was to describe somatosensory profiles in patients with degenerative lumbar spine disorders, to identify the proportion with altered somatosensory profile, and to analyze demographic characteristics, self-reported function, pain, and health pre- and 3 months post-surgery.

Methods

In this prospective cohort study in a Spine Clinic, 105 patients scheduled for surgery for spinal stenosis, disc herniation, degenerative disc disease, or spondylolisthesis were consecutively recruited. Exclusion criteria were; indication for acute surgery or previous surgery at the same spinal level or severe grade of pathology. Quantitative sensory testing (QST) and self-reported function, pain, and health was measured pre- and 3 months post-surgery. The somatosensory profile included cold detection threshold, warmth detection threshold, cold pain threshold, heat pain threshold and pressure pain threshold in affected and non-affected body regions.

Results

On a group level, the patients’ somatosensory profiles were within the 95% confidence interval (CI) from normative reference data means. On an individual level, an altered somatosensory profile was defined as having two or more body regions (including a non-affected region) with QST values outside of normal ranges for reference data. The 23 patients (22%) with altered somatosensory profiles, with mostly loss of function, were older (P = 0.031), more often female (P = 0.005), had higher back and leg pain (P = 0.016, 0.020), lower mental health component summary score (SF-36 MCS) (P = 0.004) and larger pain distribution (P = 0.047), compared to others in the cohort. Post-surgery there was a tendency to worse pain, function and health in the group with altered somatosensory profile pre-surgery.

Conclusions

On a group level, patients with degenerative lumbar spine disorders scheduled for surgery were within normal range for the QST measurements compared to reference values. On an individual level, an altered somatosensory profile outside of normal range in both affected and non-affected body regions occurred in 22% of patients, which may indicate disturbed somatosensory function. Those patients had mostly loss of sensory function and had worse self-reported outcome pre-surgery, compared to the rest of the cohort. Future prospective studies are needed to further examine whether these dimensions can be useful in predicting post-surgery outcome and guide need of additional treatments.

Fibromyalgia: A Critical and Comprehensive Review

Fibromyalgia is a disorder that is part of a spectrum of syndromes that lack precise classification. It is often considered as part of the global overview of functional somatic syndromes that are otherwise medically unexplained or part of a somatization disorder. Patients with fibromyalgia share symptoms with other functional somatic problems, including issues of myalgias, arthralgias, fatigue and sleep disturbances. Indeed, there is often diagnostic and classification overlap for the case definitions of a variety of somatization disorders. Fibromyalgia, however, is a critically important syndrome for physicians and scientists to be aware of. Patients should be taken very seriously and provided optimal care. Although inflammatory, infectious, and autoimmune disorders have all been ascribed to be etiological events in the development of fibromyalgia, there is very little data to support such a thesis. Many of these disorders are associated with depression and anxiety and may even be part of what has been sometimes called affected spectrum disorders. There is no evidence that physical trauma, i.e., automobile accidents, is associated with the development or exacerbation of fibromyalgia. Treatment should be placed on education, patient support, physical therapy, nutrition, and exercise, including the use of drugs that are approved for the treatment of fibromyalgia. Treatment should not include opiates and patients should not become poly pharmacies in which the treatment itself can lead to significant morbidities. Patients with fibromyalgia are living and not dying of this disorder and positive outlooks and family support are key elements in the management of patients.

Thermal Thresholds and Catastrophizing in Individuals with Chronic Pain after Whiplash Injury

Thermal sensitivity, thermal pain thresholds, and catastrophizing were examined in individuals with whiplash associated disorders (WAD) and in healthy pain-free participants. Quantitative sensory testing (QST) was used to measure skin sensitivity to cold and warmth and cold and heat pain thresholds over both the thenar eminence and the trapezius muscle (TrM) in 17 participants with WAD (age 50.8± 11.3 years) and 18 healthy participants (age 44.8± 10.2 years). The Pain Catastrophizing Scale (PCS) was used to determine pain coping strategies, and visual analogue scales were used for self-assessment of current background pain in individuals in the WAD group as well as experienced pain intensity and unpleasantness after QST and sleep quality in all participants. There were significant differences in warmth threshold and cold and heat pain thresholds of the TrM site between the WAD and pain-free groups. Significant differences between the two groups were also found for the catastrophizing dimension of helplessness in the PCS and in self-assessed quality of sleep. A correlational analysis showed that current background pain is significantly correlated with both cold discrimination and cold pain threshold in the skin over the TrM in individuals with WAD. These findings imply that thermal sensitivity is an important factor to consider in providing nursing care to individuals with WAD. Because biopsychosocial factors also influence the experience of pain in individuals with WAD, the role of nurses includes not only the description of the pain phenomenon but also the identification of relieving and aggravating factors.

Identifying the symptom and functional domains in patients with fibromyalgia: results of a cross-sectional Internet-based survey in Italy

Objective

The aims of this cross-sectional study were to investigate the usefulness of using an Internet survey of patients with fibromyalgia in order to obtain information concerning symptoms and functionality and identify clusters of clinical features that can distinguish patient subsets.

Methods

An Internet website has been used to collect data. Fibromyalgia Impact Questionnaire Revised version, self-administered Fibromyalgia Activity Score, and Self-Administered Pain Scale were used as questionnaires. Hierarchical agglomerative clustering was applied to the data obtained in order to identify symptoms and functional-based subgroups.

Results

Three hundred and fifty-three patients completed the study (85.3% women). The highest scored items were those related to sleep quality, fatigue/energy, pain, stiffness, degree of tenderness, balance problems, and environmental sensitivity. A high proportion of patients reported pain in the neck (81.4%), upper back (70.1%), and lower back (83.2%). A three-cluster solution best fitted the data. The variables were significantly different (P<0.0001) among the three clusters: cluster 1 (117 patients) reflected the lowest average scores across all symptoms, cluster 3 (116 patients) the highest scores, and cluster 2 (120 patients) captured moderate symptom levels, with low depression and anxiety.

Conclusion

Three subgroups of fibromyalgia samples in a large cohort of patients have been identified by using an Internet survey. This approach could provide rationale to support the study of individualized clinical evaluation and may be used to identify optimal treatment strategies.

Modulation of Cervical Facet Joint Nociception and Pain Attenuates Physical and Psychological Features of Chronic Whiplash: A Prospective Study

OBJECTIVE

To investigate changes in clinical (physical and psychological) features of individuals with chronic whiplash-associated disorder who had previously undergone cervical radiofrequency neurotomy at the time point when the effects of radiofrequency neurotomy had dissipated and pain returned.

DESIGN

Prospective cohort observational trial of consecutive patients.

SETTING

Tertiary spinal intervention centre in Calgary, Alberta, Canada.

PATIENTS

A total of 53 consecutive individuals with chronic whiplash-associated disorder.

METHODS

Individuals underwent radiofrequency neurotomy and were assessed before radiofrequency neurotomy, at 1 and 3 months postprocedure, and then after the return of pain (approximately 10 months postprocedure).

MAIN OUTCOME MEASUREMENTS

Quantitative sensory tests (pressure; thermal pain thresholds; brachial plexus provocation test), nociceptive flexion reflex, and motor function (cervical range of movement; craniocervical flexion test) were measured. Self-reported disability, psychological distress, pain catastrophization, and posttraumatic stress disorder symptoms also were measured.

RESULTS

Upon the return of pain after radiofrequency neurotomy, levels of disability increased (P < .0001), and were no different to those before radiofrequency neurotomy (P = .99). There also was a significant deterioration in quantitative sensory testing measures and reduced cervical range of motion after the return of pain (all P < .05); all approaching values were recorded before radiofrequency neurotomy (P > .22). There were no significant changes in pressure hyperalgesia (P > .054) or craniocervical flexion test performance (P > .07) after the return of pain. Psychological distress and pain catastrophizing increased significantly after the return of pain (P < .01), and again were no different than measures taken prior to radiofrequency neurotomy (P > .13). However, there was no difference in number or severity of posttraumatic stress symptoms after the return of pain (P > .30).

CONCLUSIONS

Physical and psychological features of chronic whiplash-associated disorder are modulated dynamically with cervical radiofrequency neurotomy. These findings indicate that peripheral nociception is involved in the manifestations of chronic whiplash-associated disorder in this cohort of individuals.

Do fibromyalgia patients benefit from cognitive restructuring and acceptance? An experimental study

BACKGROUND AND OBJECTIVES

The aim of this study was to clarify mechanisms of psychological fibromyalgia treatment by experimentally examining the effectiveness of its core elements. We assessed the effects of cognitive restructuring and acceptance on experimentally-induced heat and cold pain tolerance and pain intensity in fibromyalgia patients.

METHODS

Cold and heat pain were induced in a sample of 60 fibromyalgia patients using a thermode. We conducted ANCOVAs to examine group differences in posttest scores, co-varying for pretest scores. The between-groups factor was the type of instruction provided (acceptance, cognitive restructuring, and a control condition). In addition, we controlled for pain sensitivity, age, and depression.

RESULTS

We found that acceptance and cognitive restructuring were superior to the control condition in increasing heat pain tolerance, but did not differ from one another. With respect to cold pain tolerance, cognitive restructuring was associated with increases in cold pain tolerance compared to the control condition, while acceptance did not differ either from the control condition or from cognitive restructuring.

LIMITATIONS

Further experimental research on chronic pain treatment mechanisms is needed, particularly research on individually tailoring treatment strategies according to patients characteristics.

CONCLUSION

Results show that both, cognitive restructuring and acceptance instructions, enhance pain tolerance in fibromyalgia patients.