Predictors of clinical pain intensity in patients with fibromyalgia syndrome

Abnormal functional neurocircuitry underpinning emotional processing in fibromyalgia

Fibromyalgia, a condition characterized by chronic pain, is frequently accompanied by emotional disturbances. Here we aimed to study brain activation and functional connectivity (FC) during processing of emotional stimuli in fibromyalgia. Thirty female patients with fibromyalgia and 31 female healthy controls (HC) were included. Psychometric tests were administered to measure alexithymia, affective state, and severity of depressive and anxiety symptoms. Next, participants performed an emotion processing and regulation task during functional magnetic resonance imaging (fMRI). We performed a 2 × 2 ANCOVA to analyze main effects and interactions of the stimuli valence (positive or negative) and group (fibromyalgia or HC) on brain activation. Generalized psychophysiological interaction analysis was used to assess task-dependent FC of brain regions previously associated with emotion processing and fibromyalgia (i.e., hippocampus, amygdala, anterior insula, and pregenual anterior cingulate cortex [pACC]). The left superior lateral occipital cortex showed more activation in fibromyalgia during emotion processing than in HC, irrespective of valence. Moreover, we found an interaction effect (valence x group) in the FC between the left pACC and the precentral and postcentral cortex, and central operculum, and premotor cortex. These results suggest abnormal brain activation and connectivity underlying emotion processing in fibromyalgia, which could help explain the high prevalence of psychopathological symptoms in this condition.

High Prevalence of Tarsal Tunnel Syndrome in Patients Diagnosed with Fibromyalgia Syndrome

Objective To evaluate foot function and prevalence of tarsal tunnel syndrome in patients diagnosed with fibromyalgia syndrome as compared with healthy individuals.

Methods This prospective study included 111 participants, including 63 female patients with fibromyalgia (mean age: 46.17±6.64 years) and 48 female healthy controls (mean age: 46.16±9.38 years) who met the selection criteria. The participants were evaluated for Tinel’s sign and asked about the presence of foot pain and paraesthesia in both groups. In addition, the participants were assessed using the Fibromyalgia Impact Questionnaire and Foot Function Index (FFI) for functionality. Bilateral electrophysiological studies of the tibial, peroneal, sural, medial and lateral plantar nerves were performed.

Results Tarsal tunnel syndrome was present in 20 extremities of the patients with fibromyalgia (15.9%) and four extremities of the controls (4.2%)(p=0.005). Paraesthesia was observed in 56 extremities in the fibromyalgia group (44.4%) and 10 extremities in the control group (10.4%)(p<0.001). Tinel’s sign was positive in 69 extremities (54.8%) in the fibromyalgia group and 17 in the control group (17.7%)(p<0.001). The total number of painful feet was 123 (97.6%) in the fibromyalgia group and 22 (22.9%) in the control group (p<0.001). The mean total FFI was 66.26±60.80 for the right foot and 66.28±64.12 for the left foot in the FMS group; in the control group, it was 16.02±31.01 and 16.87±34.14, respectively. Both values exhibited a statistically significant difference between the two groups (p<0.001)

Conclusion In patients with fibromyalgia syndrome, paraesthesia and foot pain may be seen more frequently. Therefore, electrophysiological evaluation of the lower extremities may be recommended in these patients.

Widespread pain is a risk factor for cardiovascular mortality: results from the Framingham Heart Study

AIMS

With the introduction of widespread pain (WSP) as a separate diagnostic code in the ICD-11, WSP has now become an own clinical diagnosis independent of the underlying pathophysiology. Research has reported aetiological associations of WSP and cardiovascular diseases. However, studies on mortality risk in individuals with WSP have reported inconsistent results. This study investigates whether there is increased mortality in WSP individuals and establish potential determinants of mortality risk. Therefore, we evaluates the population-based prospective cohort of the Framingham Heart Study (FHS).

METHODS AND RESULTS

The FHS is a longitudinal multi-generational study. Pain status was assessed uniquely between 1990 and 1994. Cox proportional hazards modelling was used to estimate hazard ratios (HRs) of WSP on all-cause mortality controlling for sex and age, cardiovascular risk factors, cancer history, lifestyle factors and current medication. WSP examination was carried out in 4746 participants of the FHS (60.3 ± 13.5 years, 55.1% women). A total of 678 (14.5%) subjects fulfilled the criteria for WSP, whereas 4011 (85.5%) subjects did not. The follow-up time was 15 years, during which 202 persons died in the WSP group and 1144 in the no-WSP group. When adjusting for age and sex, all-cause mortality was increased by about 16% in WSP subjects. Individuals with WSP had an increased HR particularly for cardiovascular cause of death (HR adjusted by age and sex = 1.46, 95% confidence interval 1.10-1.94).

CONCLUSION

Our data show that in a large population-based cohort, WSP is associated with increased HR for cardiovascular cause of death, underlining the need for pain assessments in cardiovascular practice.

Neuropathic pain after thoracotomy: Tracking signs and symptoms before and at monthly intervals following surgery

BACKGROUND

As the development of neuropathic symptoms contributes to pain severity and chronification after surgery, their early prediction is important to allow targeted treatment.

OBJECTIVES

We longitudinally investigated trajectories of signs and symptoms in patients undergoing thoracotomy and assessed whether and at which time they were related to the development of neuropathic pain symptoms 6 months after surgery.

METHODS

Presurgical and 6 monthly postsurgical assessments included questionnaires for mental and physical well-being (e.g., depression/anxiety, pain catastrophizing, sleep quality, neuropathic pain symptoms), and quantitative sensory testing (QST).

RESULTS

QST trajectories indicated nerve impairment of the surgery site with predominant loss of function. Signs of recovery towards the end of the assessment period were observed for some tests. Unsupervised cluster analysis with NPSI scores 6 months after surgery as clustering variable identified one group with no/low levels of neuropathic symptoms and one with moderate levels. The two groups differed w.r.t. several signs and symptoms already at early time points. Notably, neuropathic pain anywhere in the body differed already preoperatively and sleep impairment differentiated the two groups at all time points. Regression analysis revealed three factors that seemed particularly suited to predicted 6 months NPSI scores, namely preoperative neuropathic pain symptoms, with contributions from sleep impairment 1 month after surgery and the presence of dynamic mechanical allodynia 3 months after surgery.

CONCLUSIONS

Clinical routine should focus on the individual's physiological state, including pre-existing neuropathic pain and sleep quality to identify patients early who might be at risk to develop chronic post-surgical neuropathic pain.

SIGNIFICANCE

Development of neuropathies contributes to pain severity and pain chronification after surgery. Here we demonstrate trajectories of quantitative sensory tests (assessed at monthly intervals for 6 months after surgery) that reveal accurate time courses of gain/loss of nerve function following thoracotomy. Independent of the degree of neuropathic signs after surgery, the main predictors for post-surgical neuropathic pain are self-reported neuropathic pain before surgery and sleep quality shortly after surgery.

Slowly Repeated Evoked Pain as a Marker of Central Sensitization in Fibromyalgia: Diagnostic Accuracy and Reliability in Comparison With Temporal Summation of Pain

OBJECTIVE

This study examined the diagnostic accuracy and test-retest reliability of a novel dynamic evoked pain protocol (slowly repeated evoked pain [SREP]) compared with temporal summation of pain (TSP), a standard index of central sensitization.

METHODS

Thirty-five fibromyalgia (FM) patients and 30 rheumatoid arthritis (RA) patients completed, in pseudorandomized order, a standard mechanical TSP protocol (10 stimuli of 1-second duration at the thenar eminence using a 300-g monofilament with 1 second interstimulus interval) and the SREP protocol (9 suprathreshold pressure stimuli of 5-second duration applied to the fingernail with a 30-second interstimulus interval). To evaluate reliability for both protocols, they were repeated in a second session 4-7 days later.

RESULTS

Evidence for significant pain sensitization over trials (increasing pain intensity ratings) was observed for SREP in FM (p < .001) but not in RA (p = .35), whereas significant sensitization was observed in both diagnostic groups for the TSP protocol (p < .008). Compared with TSP, SREP demonstrated higher overall diagnostic accuracy (87.7% versus 64.6%), greater sensitivity (0.89 versus 0.57), and greater specificity (0.87 versus 0.73) in discriminating between FM and RA patients. Test-retest reliability of SREP sensitization was good in FM (intraclass correlations = 0.80), and moderate in RA (intraclass correlations = 0.68).

CONCLUSIONS

SREP seems to be a dynamic evoked pain index tapping into pain sensitization that allows for greater diagnostic accuracy in identifying FM patients compared with a standard TSP protocol. Further research is needed to study mechanisms underlying SREP and the potential utility of adding SREP to standard pain evaluation protocols.

Perceived function and physical performance are associated with pain and fatigue in women with fibromyalgia

BACKGROUND

Fibromyalgia is a condition characterized by chronic widespread muscle pain and fatigue and associated with significant impairment in perceived function and reduced physical performance. The purpose of this study was to determine the degree to which pain and fatigue are associated with perceived function and physical performance in women with fibromyalgia.

METHODS

Hierarchical linear regression determined the contribution of pain and fatigue (Numeric Rating Scale (NRS) for resting, movement and combined) to perceived function (Fibromyalgia Impact Questionnaire Revised - Function Subscale, FIQR-Function), Multidimensional Assessment of Fatigue - Activities of Daily Living (MAF-ADL) and SF-36 Physical Function Subscale (SF-36-PF) and physical performance (6-Minute Walk Test, 6MWT and Five Time Sit To Stand, 5TSTS) while controlling for age, body mass index, pain catastrophizing, fear of movement, anxiety, and depression in women with fibromyalgia (N = 94).

RESULTS

For perceived function, movement pain and movement fatigue together better predicted FIQR-function (adjusted R(2) = 0.42, p ≤ 0.001); MAF-ADL (adjusted R(2) = 0.41, p ≤ 0.001); and SF-36-PF function (adjusted R(2) = 0.34, p ≤ 0.001). For physical performance measures, movement pain and fatigue together predicted 6MWT distance (adjusted R(2) = 0.42, p ≤ 0.001) and movement fatigue alone predicted performance time on the 5TSTS (adjusted R(2) = 0.20, p ≤ 0.001).

CONCLUSIONS

Pain and fatigue are significantly associated with and explain more than one-third of the variance in perceived function and physical performance in women with fibromyalgia.

TRIAL REGISTRATION

NIH Clinicaltrials.gov

REGISTRATION

NCT01888640 . Registered 13 June 2013.

Concomitance of fibromyalgia syndrome and cervical disc herniation

[Purpose] Fibromyalgia syndrome (FMS) and cervical disc herniation (CDH) are a common diseases commonly encountered in physical therapy clinics. There are also patients who have both of these diseases. In this study we aim to investigated whether FMS is a risk factor for cervical disc herniation and the frequency of their coincident occurrence. [Subjects and Methods] Thirty-five patients having a primary FMS diagnosis according to the American Rheumatism Association criteria are taken into consideration and a control group were the subjects of this study. The two groups were compared with respect to cervical disc hernia using cervical region MRI. [Results] The distribution of disc hernia of 6 fibromyalgia patients who had cervical discopathy was: 16.6% C2–3, 16.6% C5–6, 16.6% C6–7, 33.3% C4–5, C5–6 (two levels in two patients) and 16.6% C4–5, C5–6, C7–1 (three levels in one patient) . The herniation directions were given as: central in 5 levels, right paramedian in 1 level, and left paramedian disc hernia in 1 level. There were 4 cervical disk hernia in the control group. The herniation direction were central in two, right paramedian in one, and left paramedian in one patient. [Conclusion] In this study, the existence of cervical disc herniation in fibromyalgia patients was found to be not different from the normal population.

Emotional modulation of pain and spinal nociception in fibromyalgia

Fibromyalgia (FM) is characterized by widespread pain, as well as affective disturbance (eg, depression). Given that emotional processes are known to modulate pain, a disruption of emotion and emotional modulation of pain and nociception may contribute to FM. The present study used a well-validated affective picture-viewing paradigm to study emotional processing and emotional modulation of pain and spinal nociception. Participants were 18 individuals with FM, 18 individuals with rheumatoid arthritis (RA), and 19 healthy pain-free controls (HC). Mutilation, neutral, and erotic pictures were presented in 4 blocks; 2 blocks assessed only physiological-emotional reactions (ie, pleasure/arousal ratings, corrugator electromyography, startle modulation, skin conductance) in the absence of pain, and 2 blocks assessed emotional reactivity and emotional modulation of pain and the nociceptive flexion reflex (NFR, a physiological measure of spinal nociception) evoked by suprathreshold electric stimulations over the sural nerve. In general, mutilation pictures elicited displeasure, corrugator activity, subjective arousal, and sympathetic activation, whereas erotic pictures elicited pleasure, subjective arousal, and sympathetic activation. However, FM was associated with deficits in appetitive activation (eg, reduced pleasure/arousal to erotica). Moreover, emotional modulation of pain was observed in HC and RA, but not FM, even though all 3 groups evidenced modulation of NFR. Additionally, NFR thresholds were not lower in the FM group, indicating a lack of spinal sensitization. Together, these results suggest that FM is associated with a disruption of supraspinal processes associated with positive affect and emotional modulation of pain, but not brain-to-spinal cord circuitry that modulates spinal nociceptive processes.

Investigation of central pain processing in shoulder pain: converging results from 2 musculoskeletal pain models

Recent reports suggest deficits in conditioned pain modulation (CPM) and enhanced suprathreshold heat pain response (SHPR) potentially play a role in the development of chronic pain. The purpose of this study was to investigate whether central pain processing was altered in 2 musculoskeletal shoulder pain models. The goals of this study were to determine whether central pain processing: 1) differs between healthy subjects and patients with clinical shoulder pain; 2) changes with induction of exercise-induced muscle pain; and 3) changes 3 months after shoulder surgery. Fifty-eight patients with clinical shoulder pain and 56 age- and sex-matched healthy subjects were included in these analyses. The healthy cohort was examined before inducing EIMP, and 48 and 96 hours later. The clinical cohort was examined before shoulder surgery and 3 months later. CPM did not differ between the cohorts, however; SHPR was elevated for patients with shoulder pain compared to healthy controls. Induction of acute shoulder pain with EIMP resulted in increased shoulder pain intensity but did not change CPM or SHPR. Three months following shoulder surgery, clinical pain intensity decreased but CPM was unchanged from preoperative assessment. In contrast, SHPR was decreased and showed values comparable with healthy controls at 3 months. Therefore, the present study suggests that: 1) clinical shoulder pain is associated with measurable changes in central pain processing; 2) exercise-induced shoulder pain did not affect measures of central pain processing; and 3) elevated SHPR was normalized with shoulder surgery. Collectively our findings support neuroplastic changes in pain modulation were associated with decreases in clinical pain intensity only, and could be detected more readily with thermal stimuli.

PERSPECTIVE

Longitudinal studies involving quantitative sensory testing are rare. In exploring 2 musculoskeletal shoulder pain models (exercise-induced muscle pain and surgical pain), conditioned pain modulation was unchanged from pre- to post-assessment in both models. Suprathreshold heat pain response decreased after shoulder surgery and was comparable to healthy controls, suggesting this measure may be sensitive to decreases in clinical pain intensity.

Suprathreshold heat pain response is associated with clinical pain intensity for patients with shoulder pain

Quantitative sensory testing (QST) has become commonly used for the assessment of pain in subjects with clinical conditions. However, there is no consensus about which type of QST is the best predictor of clinical pain responses. The purposes of this study were to determine: a) the QST measure with the strongest association with clinical pain intensity; and b) if the QST measure continued to predict clinical pain intensity in a model including relevant psychological factors. Fifty-nine patients seeking treatment for shoulder pain underwent experimental pain assessment involving heat and pressure stimuli. The patients also completed validated questionnaires for pain intensity, pain catastrophizing, anxiety, and depression. The 5th pain rating in a series of suprathreshold heat pain stimuli accounted for a significant amount of variance in clinical pain intensity, with no other QST measure contributing to the model. The 5th pain rating remained a significant contributor to clinical pain intensity when psychological factors were included in the model. Furthermore, subjects with elevated 5th pain rating, pain catastrophizing, and depression scores had higher clinical pain intensity ratings in pre- and postoperative assessments. These data suggest that assessment of pain should include suprathreshold heat stimuli and psychological factors separately, and a combination of these factors may be predictive of pain intensity outcomes.

PERSPECTIVE

The current study provides evidence for a suprathreshold heat pain response as a clinically relevant QST measure for patients with shoulder pain, even after psychological factors were considered. The present findings suggest that the 5th pain rating from a series of suprathreshold stimuli, pain catastrophizing, and depression might play a role in predicting pain intensity outcomes.

A multi-scale view of skin thermal pain: from nociception to pain sensation

All biological bodies live in a thermal environment, including the human body, where skin is the interface with a protecting function. When the temperature is out of the normal physiological range, skin fails to protect, and the pain sensation is evoked. Furthermore, in medicine, with advances in laser, microwave and similar technologies, various thermal therapeutic methods have been widely used to cure disease/injury involving skin tissue. However, the corresponding problem of pain relief has limited further application and development of these thermal treatments. Skin thermal pain is induced through both direct (i.e. an increase/decrease in temperature) and indirect (e.g. thermomechanical and thermochemical) ways, and is governed by complicated thermomechanical-chemical-neurophysiological responses. However, a complete understanding of the underlying mechanisms is still far from clear. In this article, starting from an engineering perspective, we aim to recast the biological behaviour of skin in engineering system parlance. Then, by coupling the concepts of engineering with established methods in neuroscience, we attempt to establish multi-scale modelling of skin thermal pain through ion channel to pain sensation. The model takes into account skin morphological plausibility, the thermomechanical response of skin tissue and the biophysical and neurological mechanisms of pain sensation.

Pain-related effects of trait anger expression: neural substrates and the role of endogenous opioid mechanisms

Literature is reviewed indicating that greater tendency to manage anger via direct verbal or physical expression (trait anger-out) is associated with increased acute and chronic pain responsiveness. Neuroimaging data are overviewed supporting overlapping neural circuits underlying regulation of both pain and anger, consisting of brain regions including the rostral anterior cingulate cortex, orbitofrontal cortex, anterior insula, amygdala, and periaqueductal gray. These circuits provide a potential neural basis for observed positive associations between anger-out and pain responsiveness. The role of endogenous opioids in modulating activity in these interlinked brain regions is explored, and implications for understanding pain-related effects of anger-out are described. An opioid dysfunction hypothesis is presented in which inadequate endogenous opioid inhibitory activity in these brain regions contributes to links between trait anger-out and pain. A series of studies is presented that supports the opioid dysfunction hypothesis, further suggesting that gender and genetic factors may moderate these effects. Finally, possible implications of interactions between trait anger-out and state behavioral anger expression on endogenous opioid analgesic activity are described.

Can the neuropathic pain scale discriminate between non-neuropathic and neuropathic pain?

OBJECTIVES

1) To determine if the neuropathic pain scale (NPS) can be used to classify chronic pain patients (CPPs) as having primarily neuropathic vs non-neuropathic pain, and furthermore; 2) to determine what, if any, cut-off score can be used to reliably make this determination.

DESIGN

A total of 305 CPPs consecutive admissions to The Rosomoff Pain Center were administered the NPS and were assigned a diagnosis according to the physical examination and all available test results. CPPs with a diagnosis of chronic radiculopathy and spondylolysis/degenerative arthritis were segregated into two groups for the purposes of having a group representative of neuropathic pain (chronic radiculopathy) and non-neuropathic pain (spondylolysis/degenerative arthritis). Applying neuropathic pain criteria to each "of these two groups": a neuropathic pain "subtype" was identified within the chronic radiculopathy group; and, a non-neuropathic pain "subtype" was identified within the spondylolysis/degenerative arthritis group. This step was performed in order to assure that the CPPs selected for further analysis were truly representative of neuropathic and non-neuropathic pain. Discriminant function analysis was then employed to determine if NPS scoring could differentiate between these two "subtypes." Results from the discriminant function analysis model were utilized to derive an NPS cut-off score above which CPPs would be classified as having neuropathic pain. For the diagnoses of myofascial pain syndromes, spinal stenosis, epidural fibrosis, fibromyalgia, complex regional pain syndromes 1 and 2, and failed back surgery syndrome, a predicted NPS score was calculated and compared with the cut-off score.

SETTING

Multidisciplinary pain facility.

PATIENTS

Chronic pain patients.

RESULTS

The NPS appeared to be able to separate CPPs into neuropathic pain vs non-neuropathic pain subtypes. The derived cut-off score from the model was 5.53. Myofascial pain syndrome and spinal stenosis had predictive scores lower than this cut-off score at 3.81 and 4.26, respectively. Epidural fibrosis, fibromyalgia, complex regional pain syndromes 1 and 2, and failed back surgery syndrome had predictive scores higher than the cut-off score at 6.15, 6.35, 6.87, 9.34, and 7.19, respectively.

CONCLUSIONS

The NPS appears to be able to discriminate between neuropathic and non-neuropathic pain. A debate is currently raging as to whether diagnoses, such as fibromyalgia and complex regional pain syndrome 1, can be classified as neuropathic. Our NPS cut-off score results suggest that these diagnoses may have a neuropathic pain component. The reliability and validity of our NPS method will need to be tested further in other neuropathic pain models, such as diabetic peripheral neuropathic pain.

L-type calcium channels and NMDA receptors: a determinant duo for short-term nociceptive plasticity

In the dorsal horn of the spinal cord, pain-transmitting neurons exhibit action potential windup, a form of short-term plasticity, which consists of a progressive increase in neuronal response during repetitive stimulation of nociceptive input fibers. Windup depends on N-methyl-D-aspartate (NMDA) receptor activation, but previous in vitro studies indicated that windup also relies on intrinsic plateau properties of spinal neurons. In the present study, we considered the possible involvement of these properties in windup in vivo. For this purpose, we first studied a nociceptive flexion reflex in the rat. We showed that windup of the reflex is actually suppressed by blockers of L-type calcium current and Ca(2+)-activated non-specific cationic current (Ican), the two main depolarizing conductances of plateau potentials. We further showed that, during windup, NMDA receptors provide a critical excitatory component in a dynamic balance of excitatory and inhibitory inputs which ultimately activates L-type calcium channels. The nociceptive reflex involves at least two neuronal groups, which may express intrinsic amplification properties, motor neurons and dorsal horn neurons. By means of extracellular recordings in the dorsal horn, we showed that windup of dorsal horn neuron discharge was sensitive to the modulators of L-type calcium current. Altogether, our results suggest that, in vivo, windup also depends on the amplification properties of spinal neurons, the triggering of which requires previous activation of NMDA receptors.

Women's Health Issues with Fibromyalgia Syndrome

BACKGROUND

Fibromyalgia syndrome (FMS) involves multiple sensory, somatic, and cognitive symptoms that are bound to affect or be affected by physical and mental health status and behavioral components of daily life.

METHODS

From a telephone survey of 442 women with and 205 women without FMS as volunteers, data were compared on (1) general health status, (2) reproductive and sleep-related diagnoses, and (3) lifestyle health behaviors.

RESULTS

All multiple or logistics regression analyses for group differences were controlled for age, body mass index (BMI), race, employment status, marital status, having a college degree, low household income, and having ever been diagnosed with depression, with a Bonferroni p value correction for multiple indicators. Accordingly, FMS negatively impacted both perceived physical and mental health status, although relatively more so for physical (p < 0.017). Women with FMS were more likely to have had reproductive health or sleep-related diagnoses, including premenstrual syndrome, dysmenorrhea, breast cysts, bladder cystitis, sleep apnea, restless leg syndrome, and abnormal leg movements (p < 0.0125). They were calculated to use less than half as many calories per week as control women (689 +/- 1293 vs. 1499 +/- 1584 kcal/week, p < 0.05) and had more sleep pattern difficulties (p < 0.0125), more negative changes in sexual function (greater odds for 5 of 10 indicators at p < 0.005), and lower alcohol use (odds ratio = 0.39, p < 0.05).

CONCLUSIONS

Patients with FMS deserve careful assessment for reproductive conditions and sleep-related functional disorders. Besides more research into mechanisms underlying symptoms, intervention testing specifically to alleviate sleep problems, low physical activity levels, and sexual dysfunction should be paramount.

Overall fibromyalgia pain is predicted by ratings of local pain and pain-related negative affect—possible role of peripheral tissues

OBJECTIVES

Despite variable numbers and intensities of local pain areas, fibromyalgia (FM) patients can provide overall clinical pain ratings. We hypothesized that the overall clinical pain is largely determined by the pain intensity of local body areas. Thus, we assessed the role of local body pains as predictors of overall clinical pain in FM patients.

METHODS

Ratings of overall clinical pain intensity and pain-related negative affect (PRNA) were obtained from 277 FM patients. In addition, the patients identified painful body areas by shading a body pain diagram and rated the intensity of each pain area using a mechanical visual analogue scale (VAS). Hierarchical regression analyses were used to examine predictors of overall clinical FM pain intensity including PRNA, number of local pain areas, and maximal/average intensity of local pain areas.

RESULTS

The average overall clinical pain rating of all FM patients was 4.6 (S.D. 2.3) VAS. The PRNA accounted for 19%, number of painful body areas for 9% and maximal/average local pain for 27% of the variance of overall clinical FM pain (P-values < 0.001). The combination of all factors predicted 55% of the variance in overall clinical pain intensity of FM patients.

CONCLUSION

Peripheral factors (maximal/average local pain and number of painful body areas) predicted most of the variance of overall clinical FM pain, suggesting that the input of pain by the peripheral tissues is clinically relevant. About 19% of the pain variance was predicted by PRNA. Thus, peripheral pain and negative affect appear to be particularly relevant for overall FM pain and may represent important targets for future therapies.