R-R Interval Variation and Sympathetic Skin Response in Fibromyalgia

Novel neurophysiological evidence for preserved pain habituation across chronic pain conditions

OBJECTIVE

The present study aimed to investigate whether subjective and objective measures of pain habituation can be used as potential markers for central sensitization across various chronic pain patients.

METHODS

Two blocks of contact-heat stimuli were applied to a non-painful area in 93 chronic pain patients (low back pain, neuropathic pain, and complex regional pain syndrome) and 60 healthy controls (HC). Habituation of pain ratings, contact-heat evoked potentials (CHEP), and sympathetic skin responses (SSR) was measured.

RESULTS

There was no significant difference in any measure of pain habituation between patients and HC. Even patients with apparent clinical signs of central sensitization showed no reduced pain habituation. However, prolonged baseline CHEP and SSR latencies (stimulation block 1) were found in patients compared to HC (CHEP: Δ-latency = 23 ms, p = 0.012; SSR: Δ-latency = 100 ms, p = 0.022).

CONCLUSION

Given the performed multimodal neurophysiological testing protocol, we provide evidence indicating that pain habituation may be preserved in patients with chronic pain and thereby be of limited use as a sensitive marker for central sensitization. These results are discussed within the framework of the complex interactions between pro- and antinociceptive mechanism as well as methodological issues. The prolonged latencies of CHEP and SSR after stimulation in non-painful areas may indicate subclinical changes in the integrity of thermo-nociceptive afferents, or a shift towards antinociceptive activity. This shift could potentially affect the relay of ascending signals.

SIGNIFICANCE

Our findings challenge the prevailing views in the literature and may encourage further investigations into the peripheral and central components of pain habituation, using advanced multimodal neurophysiological techniques.

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

Background

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

Methods

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

Results

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

Conclusions

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

A Systematic Review and Meta-Analysis of the Prevalence of Small Fibre Impairment in Patients with Fibromyalgia

Converging evidence shows that patients with fibromyalgia syndrome have signs of small fibre impairment, possibly leading to pain and autonomic symptoms, with a frequency that has not yet been systematically evaluated. To fill this gap, our review aims to define the frequency of somatic and autonomic small fibre damage in patients with fibromyalgia syndrome, as assessed by objective small fibre-related testing. We found 360 articles on somatic and autonomic small fibre assessment in patients with fibromyalgia. Out of the 88 articles assessed for eligibility, 20 were included in the meta-analysis, involving 903 patients with fibromyalgia. The estimated prevalence of somatic small fibre impairment, as assessed with skin biopsy, corneal confocal microscopy, and microneurography, was 49% (95% confidence interval (CI): 39–60%, I² = 89%), whereas the estimated prevalence of autonomic small fibre impairment, as assessed with heart rate variability, sympathetic skin response, skin conductance, and tilt testing, was 45% (95% CI: 25–65%, I² = 91%). Our study shows that a considerable proportion of patients with fibromyalgia have somatic and autonomic small fibre impairment, as assessed by extensive small fibre-related testing. Nevertheless, the heterogeneity and inconsistencies across studies challenge the exact role of small fibre impairment in fibromyalgia symptoms.

Neurophysiological and ultrasonographic comparative study of autonomous nervous system in patients suffering from fibromyalgia and generalized anxiety disorder

BACKGROUND

Fibromyalgia (FM) and generalized anxiety disorder (GAD) share common clinical features: they both affect women more than men, their diagnosis is based solely on clinical criteria, and some of the symptoms such as anxiety, aches and muscle tension, sleep disorders, and cognitive dysfunction occur in both diseases. For both conditions, an underlying dysregulation of the autonomic nervous system (ANS) has been proposed.

OBJECTIVE

The aims of this study were to investigate ANS dysfunction in FM and GAD and compare them with controls.

METHODS

Sympathetic skin response (SSR) from palm and sole and cross-sectional area (CSA) of bilateral vagus nerves (VN) were measured in 28 healthy controls, 21 FM patients, and 24 GAD patients.

RESULTS

CSA of VN was significantly smaller in FM patients (right: 1.97 ± 0.74mm², left: 1.75 ± 0.65 mm2) and GAD patients (right: 2.12 ± 0.97mm², left: 1.71 ± 0.86 mm²) compared to controls (right: 3.21 ± 0.75 mm², left: 2.65 ± 1.13 mm², p < 0.001, but did not differ between the two patient groups. SSR parameters were similar between patients and controls. SSR latency correlated to clinical scales (FM Widespread Pain Index) in the FM group (r = 0.515, p = 0.02 and r = 0.447, p = 0.05) for the upper and lower limbs respectively, but no other correlation between clinical and neurophysiological parameters was identified.

CONCLUSION

This study confirms similar ANS abnormalities in FM and GAD that fairly distinguish them from controls and support the hypothesis of a common pathophysiological substrate underlying both conditions.

Pain Processing and Vegetative Dysfunction in Fibromyalgia: A Study by Sympathetic Skin Response and Laser Evoked Potentials

BACKGROUND

A dysfunction of pain processing at central and peripheral levels was reported in fibromyalgia (FM). We aimed to correlate laser evoked potentials (LEPs), Sympathetic Skin Response (SSR), and clinical features in FM patients.

METHODS

Fifty FM patients and 30 age-matched controls underwent LEPs and SSR by the right hand and foot. The clinical evaluation included FM disability (FIQ) and severity scores (WPI), anxiety (SAS) and depression (SDS) scales, and questionnaires for neuropathic pain (DN4).

RESULTS

The LEP P2 latency and amplitude and the SSR latency were increased in FM group. This latter feature was more evident in anxious patients. The LEPs habituation was reduced in FM patients and correlated to pain severity scores. In a significant number of patients (32%) with higher DN4 and FIQ scores, SSR or LEP responses were absent.

CONCLUSIONS

LEPs and SSR might contribute to clarifying the peripheral and central nervous system involvement in FM patients.

A Study on the Effects of Sympathetic Skin Response Parameters in Diagnosis of Fibromyalgia Using Artificial Neural Networks

Fibromyalgia syndrome (FMS), usually observed commonly in females over age 30, is a rheumatic disease accompanied by extensive chronic pain. In the diagnosis of the disease non-objective psychological tests and physiological tests and laboratory test results are evaluated and clinical experiences stand out. However, these tests are insufficient in differentiating FMS with similar diseases that demonstrate symptoms of extensive pain. Thus, objective tests that would help the diagnosis are needed. This study analyzes the effect of sympathetic skin response (SSR) parameters on the auxiliary tests used in FMS diagnosis, the laboratory tests and physiological tests. The study was conducted in Suleyman Demirel University, Faculty of Medicine, Physical Medicine and Rehabilitation Clinic in Turkey with 60 patients diagnosed with FMS for the first time and a control group of 30 healthy individuals. In the study all participants underwent laboratory tests (blood tests), certain physiological tests (pulsation, skin temperature, respiration) and SSR measurements. The test data and SSR parameters obtained were classified using artificial neural network (ANN). Finally, in the ANN framework, where only laboratory and physiological test results were used as input, a simulation result of 96.51 % was obtained, which demonstrated diagnostic accuracy. This data, with the addition of SSR parameter values obtained increased to 97.67 %. This result including SSR parameters - meaning a higher diagnostic accuracy - demonstrated that SSR could be a new auxillary diagnostic method that could be used in the diagnosis of FMS.

Dermatologic manifestations of fibromyalgia

The aim of this study was to determine the common dermatologic diagnoses and skin-related symptoms in a cohort of patients with fibromyalgia seen in a tertiary referral center. A retrospective chart review was performed of all patients with a fibromyalgia diagnosis from January 1 to December 31, 2008, whose diagnosis was confirmed in the Fibromyalgia and Chronic Fatigue Clinic at Mayo Clinic in Rochester, Minnesota. Charts were reviewed for dermatologic conditions and cutaneous symptoms. Demographic and clinical data were collected to assess the frequency of skin-related issues in patients with fibromyalgia. Of 2,233 patients screened, 845 patients met the inclusion criteria of having a confirmed diagnosis of fibromyalgia. Among these fibromyalgia patients, various dermatologic conditions and cutaneous problems were identified, including hyperhidrosis in 270 (32.0 %), burning sensation of the skin or mucous membranes in 29 (3.4 %), and various unusual cutaneous sensations in 14 (1.7 %). Pruritus without identified cause was noted by 28 patients (3.3 %), with another 16 patients (1.9 %) reporting neurotic excoriations, prurigo nodules, or lichen simplex chronicus. Some form of dermatitis other than neurodermatitis was found in 77 patients (9.1 %). Patients with fibromyalgia may have skin-related symptoms associated with their fibromyalgia. No single dermatologic diagnosis appears to be overrepresented in this population, with the exception of a subjective increase in sweating.

The subclinic autonomic dysfunction in patients with Behçet disease: an electrophysiological study

Studies that have evaluated autonomic nervous system (ANS) function in Behçet disease (BD) are rare and have indicated conflicting results with different degrees of involvement. The aim of this study was to investigate ANS function by using electrophysiological tests in patients with BD and to determine the relationship between the disease activity parameters and the indicators of autonomic activity. We included 70 BD patients and 50 healthy controls. Demographic characteristics including age, sex, and disease duration were recorded. A detailed neurological examination was performed, and clinical autonomic symptoms were recorded. The Behçet Disease Current Activity Form (BDCAF) was used to determine the disease activity. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels were determined for laboratory activity. The electrophysiological assessments of ANS function were performed by sympathetic skin response (SSR) and R-R interval variation (RRIV) tests. The mean values of sympathetic (SSR latency and amplitude) and parasympathetic (RRIV at rest [R%] and deep breathing [D%], D% - R%, and D%/R%) parameters were compared, and any correlations between ANS parameters and clinical disease characteristics were determined. Seventy BD patients (23 males, 47 females) with a mean age of 41.2 ± 10.01 years and 50 control subjects (18 males, 32 females) with a mean age of 39.5 ± 8.94 years were included in the study. All the subjects were totally symptom free with respect to ANS involvement, and the subjects in both groups had normal neurological examination findings. The demographic characteristics were similar between the groups. The mean latency of SSR was increased (1.4 ± 0.4 vs 0.7 ± 0.8), and R% (0.3 ± 0.3 vs 0.5 ± 0.4) and D% (0.3 ± 0.3 vs 0.6 ± 0.5) values were decreased in BD patients compared to control subjects. No correlation was found between BDCAF scores and ANS variables. However, there was a significant correlation between SSR latency and ESR and CRP values (p < 0.01, r = -0.25, r = -0.31, respectively) in the patient group, indicating a more sympathetic dysautonomia in patients with active laboratory parameters. In conclusion, our study indicates a subclinical sympathetic and parasympathetic autonomic dysfunction in patients with BD, which may be related with disease activity. As the early recognition of abnormalities in ANS may be very important in order to prevent excessive morbidity, simple electrophysiological methods are suggested to identify Behçet patients at high risk for symptomatic dysautonomia.

Mindfulness meditation for symptom reduction in fibromyalgia: psychophysiological correlates

OBJECTIVES

Fibromyalgia, a chronic pain syndrome, is often accompanied by psychological distress and increased basal sympathetic tone. In a previous report it was shown that mindfulness-based stress-reduction (MBSR) reduced depressive symptoms in patients with fibromyalgia with gains maintained at two months follow-up (Sephton et al., Arthr Rheum 57:77-85, 2007). This second study explores the effects of MBSR on basal sympathetic (SNS) activation among women with fibromyalgia.

METHODS

Participants (n = 24) responded to a television news appearance, newspaper, and radio advertisements. Effects on anxiety, depressive symptoms, and SNS activation measures were tested before and after MBSR using a within-subjects design.

RESULTS

The MBSR treatment significantly reduced basal electrodermal (skin conductance level; SCL) activity (t = 3.298, p = .005) and SCL activity during meditation (t = 4.389, p = .001), consistent with reduced SNS activation.

CONCLUSIONS

In this small sample, basal SNS activity was reduced following MBSR treatment. Future studies should assess how MBSR may help reduce negative psychological symptoms and attenuate SNS activation in fibromyalgia. Further clarification of psychological and physiological responses associated with fibromyalgia may lead to more beneficial treatment.

Violence, stress, and somatic syndromes

Syndromes characterized by pain, fatigue, mood disorder, cognitive dysfunction, and sleep disturbance have been referred to as stress-related somatic disorders by virtue of the observation that onset and exacerbation of symptoms occur with stress. These syndromes include but are not limited to fibromyalgia, chronic fatigue syndrome, temporomandibular disorder, and irritable bowel syndrome. As with most chronic illnesses, genetic susceptibility and lifetime environmental exposures play a role in creating vulnerability to disease. Cumulative lifetime stress has been associated with a number of physiologic changes in the brain and body that reflect dysregulated hormonal and autonomic activity. Exposure to the stressor of violence is likely to create a state of vulnerability for the stress-related somatic syndromes and also to contribute to symptom expression and severity. Understanding the relationship between violence, stress, and somatic syndromes will help in clarifying the consequences of violence exposure to long-term health and health-related quality of life.

Hypothesis: the chaos and complexity theory may help our understanding of fibromyalgia and similar maladies

BACKGROUND

Modern clinicians are often frustrated by their inability to understand fibromyalgia and similar maladies since these illnesses cannot be explained by the prevailing linear-reductionist medical paradigm.

OBJECTIVE

This article proposes that new concepts derived from the Complexity Theory may help understand the pathogenesis of fibromyalgia, chronic fatigue syndrome, and Gulf War syndrome.

METHODS

This hypothesis is based on the recent recognition of chaos fractals and complex systems in human physiology.

RESULTS

These nonlinear dynamics concepts offer a different perspective to the notion of homeostasis and disease. They propose that the essence of disease is dysfunction and not structural damage. Studies using novel nonlinear instruments have shown that fibromyalgia and similar maladies may be caused by the degraded performance of our main complex adaptive system. This dysfunction explains the multifaceted manifestations of these entities.

CONCLUSIONS

To understand and alleviate the suffering associated with these complex illnesses, a paradigm shift from reductionism to holism based on the Complexity Theory is suggested. This shift perceives health as resilient adaptation and some chronic illnesses as rigid dysfunction.