Central sensitization: a biopsychosocial explanation for chronic widespread pain in patients with fibromyalgia and chronic fatigue syndrome

Effect of dipyrone and thalidomide alone and in combination on STZ-induced diabetic neuropathic pain

Diabetic neuropathy is recognized as one of the most common complications of chronic diabetes, but its pathophysiological mechanism is complex and yet to be completely explored. Monotherapy with conventional analgesics fails to provide adequate pain relief in peripheral diabetic neuropathy. There are a number of evidence suggesting that tumor necrosis factor (TNF-α) plays an important role in the pathogenesis of peripheral diabetic neuropathy. TNF-α up-regulation activates nuclear factor κB, which further up-regulates cyclooxygenase (COX)-2 leading to altered prostaglandin profile. Inhibition of TNF-α and COX-2 provides beneficial effect on diabetic neuropathy by decreasing the oxidative stress level and by preventing neuronal hypersensitivity due to an increased prostaglandin level. The present study was designed to assess the effect of dipyrone and thalidomide on streptozotocin (STZ)-induced neuropathic pain behavior in rats. STZ 50 mg/kg, i.p. was administered to induce experimental diabetes in the rats. Three weeks following STZ, dipyrone (300 and 600 mg/kg, i.p.) and thalidomide (25 and 50 mg/kg, i.p.) alone and subeffective dose combination of dipyrone and thalidomide (300 and 25 mg/kg(-1), i.p.) administered daily for 2 weeks significantly attenuated thermal hyperalgesia, mechanical allodynia, and formalin-induced phase-2 flinching response. Moreover, the subeffective dose combination of dipyrone and thalidomide and preemptive treatment with thalidomide (50 mg/kg) reduces oxidative stress in diabetic rats. In conclusion, the combination of subeffective dose of dipyrone and thalidomide prevented the development and maintenance of experimental diabetic neuropathy. The combination of thalidomide (TNF-α inhibitor) and dipyrone (COX inhibitor) may be used as a potential therapeutic agent for the treatment of diabetic neuropathy.

Delineating psychological and biomedical profiles in a heterogeneous fibromyalgia population using cluster analysis

The heterogeneity of patients meeting American College of Rheumatology (ACR) criteria for a diagnosis of fibromyalgia (FM) challenges our ability to understand the underlying pathogenesis and to optimize treatment of this enigmatic disorder. Our goal was to discern clinically relevant subgroups across multiple psychological and biomedical domains to better characterize the phenomenology of FM. Women meeting 1990 ACR criteria for FM (N = 107) underwent psychological (childhood trauma, mood, anxiety, and stress) and biomedical (neuroendocrine, immune, and metabolic) testing. Cluster analysis identified four distinct subgroups. Subgroups I, II, and III exhibited profiles that included high psychological distress. Subgroup I was further distinguished by a history of childhood maltreatment and hypocortisolism, and these women reported the most pain and disability. Subgroup II evinced more physiological dysregulation and also reported high levels of pain, fatigue, and disability. Subgroup III was characterized by normal biomarkers and reported intermediate pain severity with higher global functioning. Subgroup IV was distinguished by their psychological well-being, reporting less disability and pain. Our findings underscore the heterogeneity of both psychological and physiological features among FM patients presenting with nearly identical tender point counts. This subgroup categorization is compatible with hypothesized pathogenetic mechanisms of early trauma, stress system dysregulation, and pro-inflammatory bias, each prominent in some but not all FM patients. Appreciation of distinct FM subgroup features is invaluable for selecting the most appropriate treatment modalities.

Ten sessions of adjunctive left prefrontal rTMS significantly reduces fibromyalgia pain: a randomized, controlled pilot study

Transcranial magnetic stimulation (TMS) of the prefrontal cortex can cause changes in acute pain perception. Several weeks of daily left prefrontal TMS has been shown to treat depression. We recruited 20 patients with fibromyalgia, defined by American College of Rheumatology criteria, and randomized them to receive 4000 pulses at 10 Hz TMS (n=10), or sham TMS (n=10) treatment for 10 sessions over 2 weeks along with their standard medications, which were fixed and stable for at least 4 weeks before starting sessions. Subjects recorded daily pain, mood, and activity. Blinded raters assessed pain, mood, functional status, and tender points weekly with the Brief Pain Inventory, Hamilton Depression Rating Scale, and Fibromyalgia Impact Questionnaire. No statistically significant differences between groups were observed. Patients who received active TMS had a mean 29% (statistically significant) reduction in pain symptoms in comparison to their baseline pain. Sham TMS participants had a 4% nonsignificant change in daily pain from their baseline pain. At 2 weeks after treatment, there was a significant improvement in depression symptoms in the active group compared to baseline. Pain reduction preceded antidepressant effects. TMS was well tolerated, with few side effects. Further studies that address study limitations are needed to determine whether daily prefrontal TMS may be an effective, durable, and clinically useful treatment for fibromyalgia symptoms.

Is appreciation of written education about pain neurophysiology related to changes in illness perceptions and health status in patients with fibromyalgia?

OBJECTIVE

To investigate the appreciation of written education about pain neurophysiology in patients with fibromyalgia (FM) and its effects on illness perceptions and perceived health status.

METHODS

A booklet explaining pain neurophysiology was sent to participants with FM. Appreciation was assessed with 10 questions addressing relevance (0-30) and reassurance (0-30). Illness perceptions, catastrophizing and health status were measured with the Revised Illness Perception Questionnaire (IPQ-R), the Pain Catastrophizing Scale (PCS) and the Fibromyalgia Impact Questionnaire (FIQ) at baseline (T0), after a 2-week control period (T1) and 6 weeks after the intervention (T2).

RESULTS

Forty-one patients participated. Mean (SD) scores for relevance and reassurance were 21.6 (5.6) and 18.7 (5.7), respectively. Only illness coherence, emotional representations, pain and fatigue changed significantly between T0 and T2. Correlations between appreciation and changes in outcomes ranged between r=0.00 and r=0.34.

CONCLUSIONS

Although a majority of subjects appreciated the written information, it did not have clinically relevant effects on illness perceptions, catastrophizing or impact of FM on daily life.

PRACTICE IMPLICATIONS

Written education about pain neurophysiology is inadequate toward changing illness perceptions, catastrophizing or perceived health status of participants with FM; education should be incorporated into a broader multidisciplinary self-management program.

Toll-like receptors in chronic pain

Proinflammatory central immune signaling contributes significantly to the initiation and maintenance of heightened pain states. Recent discoveries have implicated the innate immune system, pattern recognition Toll-like receptors in triggering these proinflammatory central immune signaling events. These exciting developments have been complemented by the discovery of neuronal expression of Toll-like receptors, suggesting pain pathways can be activated directly by the detection of pathogen associated molecular patterns or danger associated molecular patterns. This review will examine the evidence to date implicating Toll-like receptors and their associated signaling components in heightened pain states. In addition, insights into the impact Toll-like receptors have on priming central immune signaling systems for heightened pain states will be discussed. The influence possible sex differences in Toll-like receptor signaling have for female pain and the recognition of small molecule xenobiotics by Toll-like receptors will also be reviewed.

Central amplification and fibromyalgia: disorder of pain processing

Fibromyalgia (FM), a complex chronic pain disorder affecting a heterogeneous patient population, is an area of active basic and clinical research. Although diagnostic criteria for FM have been available for 2 decades, there remains no definitive diagnostic and no consensus regarding its etiology. Accumulating evidence suggests the underlying cause of FM pain results from abnormal pain processing particularly in the central nervous system rather than from dysfunction in peripheral tissues where pain is perceived. In this review, we examine recent studies investigating abnormalities in central pain processing as a component of FM in both preclinical models of generalized muscle hypersensitivity and clinical research in patients with FM. We focus our discussion on two areas where strong evidence exists for abnormalities in sensory signaling: the reduction of descending control, including suppression of descending inhibitory pathways and/or enhancement of descending facilitatory pathways, and changes in key neurotransmitters associated with central sensitization. Finally, we discuss currently available pharmacological treatments indicated for the management of pain in FM patients, based on their proposed mechanism of action and efficacy.

Electrophysiologic evidence of spinal accessory neuropathy in patients with cervical myofascial pain syndrome

OBJECTIVE

To evaluate whether or not spinal accessory neuropathy exists in patients with cervical myofascial pain syndrome (MFPS).

DESIGN

Prospective study.

SETTING

A neurophysiologic laboratory in a university hospital.

PARTICIPANTS

Patients with cervical MFPS (n=25) and healthy controls (n=20).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We performed nerve conduction studies (NCSs) in bilateral spinal accessory nerves, and electromyography and stimulated single-fiber electromyography in the trapezius muscles of all patients and controls. Parameters including nerve conduction velocities (NCVs), amplitudes and areas of compound muscle action potentials (CMAPs), and mean consecutive differences (MCDs) in single-fiber electromyography were measured, analyzed, and compared with the disease durations of the patients.

RESULTS

Spinal accessory NCSs showed normative NCVs but with prominently reduced CMAP amplitude in the patients with cervical MFPS, which is recognized as an axonal neuropathy of the spinal accessory nerves. Electromyography showed prominent evidence of denervation and reinnervation patterns in 48% of the MFPS patients. The abnormal MCDs in single-fiber electromyography indicated a synaptic delay of motor endplates in the motor units, and may signify evolving instability of neuromuscular transmission in the spinal accessory nerves innervating trapezius muscles of the patients.

CONCLUSIONS

This study demonstrates electrophysiologic evidence of neuroaxonal degeneration and neuromuscular transmission disorder in a significant proportion of patients with cervical MFPS. We suggest that spinal accessory neuropathy may be associated with cervical MFPS.

The efficacy of tramadol/acetaminophen combination tablets (Ultracet®) as add-on and maintenance therapy in knee osteoarthritis pain inadequately controlled by nonsteroidal anti-inflammatory drug (NSAID)

The purpose of this study is to compare the efficacy of tramadol 37.5 mg/acetaminophen 325 mg combination tablets (tramadol/APAP) with that of nonsteroidal anti-inflammatory drugs (NSAIDs) as maintenance therapy following tramadol/APAP and NSAID combination therapy in knee osteoarthritis (OA) pain which was inadequately controlled by NSAIDs. Subjects with knee OA for over 1 year and moderate pain (numerical rating scale [NRS] ≥5) despite at least 4 weeks' NSAID therapy (meloxicam 7.5 mg or 15 mg qd or aceclofenac 100 mg bid) received tramadol/APAP add-on (combination with NSAID) for 4 weeks. Thereafter, subjects with significant pain improvement (NRS <4) were randomized to receive either tramadol/APAP or NSAID for 8 weeks. On days 29 and 57, Western Ontario and McMaster Universities (WOMAC) OA index score was measured. Secondary measures included pain intensity (NRS), pain relief score, and subjects' and investigators' overall medication assessments. Of 143 subjects enrolled, 112 completed the 4-week tramadol/APAP and NSAID combination phase and 97 (67.8%) experienced significant pain improvement. Of the 97 subjects randomized, 36 in tramadol/APAP group and 47 in NSAID group completed the 8-week comparator study. On days 29 and 57, WOMAC scores and pain intensities did not increase in both groups compared to measurements immediately after the combination therapy. At these two time points, there were no significant differences in WOMAC scores, pain intensities, and other secondary measures between the two groups. Overall adverse event rates were similar in both groups. Tramadol/APAP add-on significantly improved knee OA pain which had been inadequately controlled by NSAIDs. In those subjects who showed favorable response to tramadol/APAP and NSAID combination therapy, both tramadol/APAP and NSAIDs were effective at maintaining the pain-reduced state and there was no significant difference in efficacy between tramadol/APAP and NSAIDs.

Stress enhances muscle nociceptor activity in the rat

Chronic widespread pain, such as observed in irritable bowel (IBS) and fibromyalgia (FMS) syndrome, are markedly affected by stress. While such forms of stress-induced hyperalgesia are generally considered manifestations of "central sensitization," recent studies in patients with IBS and FMS suggest an additional, peripheral contribution. To examine the effect of stress on muscle nociceptor function, we evaluated activity in nociceptors innervating the gastrocnemius muscle in an animal model of chronic widespread pain, water avoidance stress, in the rat. This stressor, which produces mechanical hyperalgesia in skeletal muscle produced a significant decrease (∼34%) in mechanical threshold of muscle nociceptors and a marked, ∼two-fold increase in the number of action potentials produced by a prolonged (60 s) fixed intensity suprathreshold 10 g stimulus. Stress also induced an increase in conduction velocity from 1.25 m/s to 2.09 m/s, and increased variability in neuronal activity. Given that these changes, each of at least moderate magnitude, would be expected to enhance nociceptor activity, it is likely that, taken together, they contribute to the enhanced nociception observed in this model of stress-induced chronic widespread pain.

Central sensitivity syndromes: mounting pathophysiologic evidence to link fibromyalgia with other common chronic pain disorders

The aim of this study was to review emerging data from the fields of nursing, rheumatology, dentistry, gastroenterology, gynecology, neurology, and orthopedics that support or dispute pathophysiologic similarities in pain syndromes studied by each specialty. A literature search was performed through PubMed and Ovid using the terms fibromyalgia, temporomandibular joint disorder, irritable bowel syndrome, irritable bladder/interstitial cystitis, headache, chronic low back pain, chronic neck pain, functional syndromes, and somatization. Each term was linked with pathophysiology and/or central sensitization. This paper presents a review of relevant articles with a specific goal of identifying pathophysiologic findings related to nociceptive processing. The extant literature presents considerable overlap in the pathophysiology of these diagnoses. Given the psychosomatic lens through which many of these disorders are viewed, demonstration of evidence-based links supporting shared pathophysiology between these disorders could provide direction to clinicians and researchers working to treat these diagnoses. "Central sensitivity syndromes" denotes an emerging nomenclature that could be embraced by researchers investigating each of these disorders. Moreover, a shared paradigm would be useful in promoting cross-fertilization between researchers. Scientists and clinicians could most effectively forward the understanding and treatment of fibromyalgia and other common chronic pain disorders through an appreciation of their shared pathophysiology.

Treatment of central sensitization in patients with 'unexplained' chronic pain: what options do we have?

INTRODUCTION

Central sensitization accounts for chronic 'unexplained' pain in a wide variety of disorders, including chronic whiplash-associated disorders, temporomandibular disorders, chronic low back pain, osteoarthritis, fibromyalgia, chronic fatigue syndrome and chronic tension-type headache among others. Given the increasing evidence supporting the clinical significance of central sensitization in those with unexplained chronic pain, the awareness is growing that central sensitization should be a treatment target in these patients.

AREAS COVERED

This article provides an overview of the treatment options available for desensitizing the CNS in patients with chronic pain due to central sensitization. It focuses on those strategies that specifically target pathophysiological mechanisms known to be involved in central sensitization. In addition, pharmacological options, rehabilitation and neurotechnology options are discussed.

EXPERT OPINION

Acetaminophen, serotonin-reuptake inhibitor drugs, selective and balanced serototin and norepinephrine-reuptake inhibitor drugs, the serotonin precursor tryptophan, opioids, N-methyl-d-aspartate (NMDA)-receptor antagonists, calcium-channel alpha(2)delta (a2δ) ligands, transcranial magnetic stimulation, transcutaneous electric nerve stimulation (TENS), manual therapy and stress management each target central pain processing mechanisms in animals that - theoretically - desensitize the CNS in humans. To provide a comprehensive treatment for 'unexplained' chronic pain disorders characterized by central sensitization, it is advocated to combine the best evidence available with treatment modalities known to target central sensitization.

Differential effects of painful and non-painful stimulation on tactile processing in fibromyalgia syndrome and subjects with masochistic behaviour

BACKGROUND

In healthy subjects repeated tactile stimulation in a conditioning test stimulation paradigm yields attenuation of primary (S1) and secondary (S2) somatosensory cortical activation, whereas a preceding painful stimulus results in facilitation.

METHODOLOGY/PRINCIPAL FINDINGS

Since previous data suggest that cognitive processes might affect somatosensory processing in S1, the present study aims at investigating to what extent cortical reactivity is altered by the subjective estimation of pain. To this end, the effect of painful and tactile stimulation on processing of subsequently applied tactile stimuli was investigated in patients with fibromyalgia syndrome (FMS) and in subjects with masochistic behaviour (MB) by means of a 122-channel whole-head magnetoencephalography (MEG) system. Ten patients fulfilling the criteria for the diagnosis of FMS, 10 subjects with MB and 20 control subjects matched with respect to age, gender and handedness participated in the present study. Tactile or brief painful cutaneous laser stimuli were applied as conditioning stimulus (CS) followed by a tactile test stimulus (TS) 500 ms later. While in FMS patients significant attenuation following conditioning tactile stimulation was evident, no facilitation following painful stimulation was found. By contrast, in subjects with MB no attenuation but significant facilitation occurred. Attenuation as well as facilitation applied to cortical responses occurring at about 70 ms but not to early S1 or S2 responses. Additionally, in FMS patients the amount of attenuation was inversely correlated with catastrophizing tendency.

CONCLUSION

The present results imply altered cortical reactivity of the primary somatosensory cortex in FMS patients and MB possibly reflecting differences of individual pain experience.

Primary care physical therapy in people with fibromyalgia: opportunities and boundaries within a monodisciplinary setting

Despite the fact that people with fibromyalgia syndrome (FMS) frequently are seen by primary care physical therapists, guidelines for the management of FMS are based primarily on outcomes from multidisciplinary and tertiary care treatment studies. Few data addressing the treatment of patients with FMS in primary care currently are available. The evidence-based guidelines on the management of FMS are based, in part, on evidence from studies examining physical therapy treatment components alone (eg, aerobic exercise, education). Thus, the recommendations can be applied to primary care physical therapy. Primary care physical therapy for patients with FMS should include education, aerobic exercise, and strengthening exercise. For other treatment components such as passive treatments, activity management, and relaxation, less evidence currently is available to advocate their use in primary care physical therapy. Superior results are to be expected when various treatment components are combined.

The search for pain relief in people with chronic fatigue syndrome: a descriptive study

The purpose of this study was to investigate the use and perceived benefit of complimentary and alternative medicine (CAM) and physiotherapy treatments tried by people with chronic fatigue syndrome (CFS) to ease painful symptoms. This study used a descriptive, cross-sectional design. People with CFS who experienced pain were recruited to this study. Participants were asked during a semistructured interview about the treatments they had tried to relieve their pain. Each interview was conducted in the home of the participant. Fifty participants were recruited, of which, 10 participants were severely disabled by CFS. Eighteen participants were trying different forms of CAM treatment for pain relief at the time of assessment. Three participants were currently receiving physiotherapy. Throughout the duration of their illness 45 participants reported trying 19 different CAM treatments in the search for pain relief. Acupuncture was reported to provide the most pain relief (n=16). Twenty-seven participants reported a total of 16 different interventions prescribed by their physiotherapist. The results of this study suggest some physiotherapy and CAM treatments may help people manage painful CFS symptoms. Future research should be directed to evaluating the effectiveness of interventions such as acupuncture or gentle soft tissue therapies to reduce pain in people with CFS.

Clinical and personality features of allodynic migraine

Cutaneous allodynia (CA) is a frequent complaint during migraine attacks, recently associated with migraine transformation as well as psychiatric comorbidities. The aim of our study was to define the clinical features of allodynic migraineurs, in particular, the relationship between CA and personality profile. Between October 2008 and December 2009, 410 migraineurs admitted for the first time to our Headache Center underwent Allodynia Symptom Checklist, MIgraine DIsability Assessment Scale (MIDAS) and psychometric tests [Tridimensional Personality Questionnaire (TPQ), Toronto Alexithymia Scale, State and Trait Anxiety Inventory (STAI Y 1-2), and Beck Depression Inventory (BDI)]. Allodynia was present in 63% of cases, mostly in females. In CA patients, an association with female sex, chronic migraine, higher values of MIDAS, BDI, harm avoidance (HA, a TPQ dimension) and STAI Y-2 was found. Interestingly, CA appears to be associated with depression and a particular personality profile characterized by higher values of HA, suggesting an involvement of the serotonergic system in the development of CA in migraine. In conclusion, CA is associated with progression of migraine and it could be a marker of psychiatric comorbidities, in particular, depression and anxious trait.

Evidence for generalized hyperalgesia in chronic fatigue syndrome: a case control study

Several studies provided evidence for generalized hyperalgesia in fibromyalgia or whiplash-associated disorders. In chronic fatigue syndrome, however, pain is a frequently reported complaint, but up to now, evidence for generalized hyperalgesia is lacking. The aim of this study is to examine whether the pressure pain thresholds (PPTs) at both symptomatic and asymptomatic sites differ in chronic fatigue syndrome (CFS) patients with chronic pain, compared to healthy controls. Therefore, 30 CFS patients with chronic pain and 30 age- and gender-matched healthy controls indicated on a Margolis Pain Diagram where they felt pain lasting longer than 24 h in the past 4 weeks. After completing a test battery of questionnaires evaluating pain cognitions, functional status and symptomatology, a blinded researcher assessed PPTs bilaterally at seven nonspecific sites on both trunk and extremities. PPTs were compared for the two complete groups. In addition, PPTs of patients and controls who did not report pain in a respective zone were compared. PPTs of the patients were significantly lower (p<0.001) compared to those of the control group, also when pain-free samples per zone were compared (p<0.001). The mean PPT was 3.30 kg/cm2 in all CFS patients and 8.09 kg/cm2 in the controls. No confounding factors responsible for the observed differences, as, e.g., catastrophizing and depression, could be revealed. These findings provide evidence for the existence of hyperalgesia even in asymptomatic areas (generalized secondary hyperalgesia). The generalized hyperalgesia may represent the involvement of a sensitized central nervous system.

Deviations in the endocrine system and brain of patients with fibromyalgia: cause or consequence of pain and associated features?

The brain and endocrine system are crucial interfaces responding to pathological and psychological processes. This review discusses whether endocrine deviations and structural and functional changes in the brain are a cause or consequence of fibromyalgia. Studies in patients with fibromyalgia virtually uniformly observed subtle alterations in hypothalamic pituitary adrenal functioning, hyporeactive autonomic nervous system responsiveness to stressors, and structural and functional changes in the brain. Our model proposes that predisposing factors, such as genetic vulnerability and trauma, have led to an alteration of the nociceptive system including several neuroendocrine changes. The resulting pain and associated symptoms, such as sleep disturbance, low fitness, fatigue, stress, and distress, are a cause of new neuroendocrine changes. The model predicts that favorable neuroendocrine changes are to be expected after successful pharmacological or non-pharmacological interventions that target pain and associated symptoms.

Increased basal mechanical pain sensitivity but decreased perceptual wind-up in a human model of relative hypocortisolism

Clinical data have accumulated showing that relative hypocortisolism, which may be regarded as a neuroendocrinological correlate of chronic stress, may be a characteristic of some functional pain syndromes. However, it has not been clarified yet whether deregulations of the hypothalamus-pituitary-adrenal (HPA) axis may directly alter pain perception and thus be causally involved in the pathophysiology of these disorders. To test this hypothesis, we performed a randomized placebo-controlled crossover trial in N=20 healthy drug-free volunteers (median age 24yrs) and analyzed the effects of metyrapone-induced hypocortisolism on quantitatively assessed basal mechanical pain sensitivity (1.5-13m/s impact stimuli), perceptual wind-up (9m/s impact stimuli at 1Hz) and temporal summation of pain elicited by inter-digital web pinching (IWP; 10N pressure stimuli for 2min). Experimentally induced hypocortisolism significantly decreased pain detection thresholds and augmented temporal summation of IWP-induced pain (p<.05). The latter effect was dependent on the relative reduction in cortisol levels, and seemed to rely on a potentiated sensitization and not merely on the observed changes in basal pain sensitivity. Perceptual wind-up by contrast was reduced when cortisol synthesis was blocked (p<.05). This result is reminiscent of findings from animal studies showing a reversal of NMDA receptor activation by glucocorticoid receptor antagonists in neuropathic pain models. Our results speak in favor of a potential causal role of HPA axis alterations in pain chronicity.

The long-term costs of traumatic stress: intertwined physical and psychological consequences

The gradual emergence of symptoms following exposure to traumatic events has presented a major conceptual challenge to psychiatry. The mechanism that causes the progressive escalation of symptoms with the passage of time leading to delayed onset post-traumatic stress disorder (PTSD) involves the process of sensitization and kindling. The development of traumatic memories at the time of stress exposure represents a major vulnerability through repeated environmental triggering of the increasing dysregulation of an individual's neurobiology. An increasing body of evidence demonstrates how the increased allostatic load associated with PTSD is associated with a significant body of physical morbidity in the form of chronic musculoskeletal pain, hypertension, hyperlipidaemia, obesity and cardiovascular disease. This increasing body of literature suggests that the effects of traumatic stress need to be considered as a major environmental challenge that places individual's physical and psychological health equally at risk. This broader perspective has important implications for developing treatments that address the underlying dysregulation of cortical arousal and neurohormonal abnormalities following exposure to traumatic stress.

Fibromyalgia: From treatment to rehabilitation

Fibromyalgia is a clinical syndrome of chronic widespread pain and reduced pain thresholds to palpation. The pathophysiology remains unknown, but there is increasing evidence that peripheral and central sensitization cause an amplification of sensory impulses that may alter pain perception in fibromyalgia patients. Interventions to treat fibromyalgia should aim at different targets simultaneously in order to reduce peripheral and central sensitization. There are both pharmacologic and non-pharmacologic approaches with evidence for effectiveness in the treatment of fibromyalgia and its associated symptoms. Evidence from randomized trials and meta-analyses shows that partial and short-term improvements in fibromyalgia symptoms can be achieved with low doses of antidepressants and with physical activity such as aerobic and strengthening exercises. A multidimensional approach which emphasizes education and integration of exercise and cognitive behavior therapy improves quality of life and reduces pain, fatigue and depressive symptoms when measured on a short term basis. More recently, trials have shown the neuromodulators gabapentin and pregabalin to be effective in reducing pain and improving quality of sleep in fibromyalgia. In addition, small trials of noninvasive brain stimulation have also shown benefits in reducing pain in fibromyalgia. It is essential to keep in mind that some important clinical conditions can mimic and overlap with fibromyalgia and should always be ruled out by a complete history, physical examination and appropriate laboratory testing.

Sensory perception thresholds in men with chronic pelvic pain syndrome

OBJECTIVES

To compare sensory thresholds in different nerve-fiber types in men with chronic pelvic pain syndrome (CPPS) and healthy controls, using thermal sensory testing and measuring current perception thresholds (CPT).

METHODS

We enrolled 22 men with CPPS and 20 healthy control participants. We determined the thermal sensory perception thresholds of C and Adelta nerve fibers on the perineum and left posterior thigh. To test CPT, we used sine wave electrical stimulation at 5, 250, and 2000 Hz, resulting in the selective depolarization of small unmyelinated C fibers, small myelinated Adelta, and large myelinated Abeta fibers, respectively. We bilaterally tested the hypothenar surface of the palms, medial parts of soles, midshaft of penis, and 1 site in the midperineum, for a total of 7 sites.

RESULTS

The mean age of men with CPPS was similar to that of controls [42.8 (standard deviation, 9.4) and 40.4 (standard deviation, 13.2) years, respectively, P = .548]. There was no significant difference between the 2 groups for thermal perception thresholds in both the perineum and left thigh (P >.05). There was also no difference between the 2 groups for CPT values of all 3 frequencies of stimuli in each area tested (P >.05 for all comparisons).

CONCLUSIONS

The absence of sensory threshold differences between men with CPPS and controls, with either thermal stimulation of C and Adelta fiber afferents or electrical stimulation of C, Adelta, and Abeta fiber afferents, discounts the existence of a peripheral neuropathy as a cause for pain in men with CPPS.

Combined use of pregabalin and memantine in fibromyalgia syndrome treatment: a novel analgesic and neuroprotective strategy?

Fibromyalgia syndrome (FMS) is a chronic widespread pain syndrome that is estimated to affect 4-8 million US adults. The exact molecular mechanisms underlying this illness remain unclear, rendering most clinical treatment and management techniques relatively ineffective. It is now known that abnormalities in both nociceptive and central pain processing systems are necessary (but perhaps not sufficient) to condition the onset and maintenance of FMS. These same systemic abnormalities are thought to be responsible for the loss of cephalic gray matter density observed in all FMS patients groups studied to date. The current scope of FMS treatment focuses largely on analgesia and does not clearly address potential neuroprotective strategies. This article proposes a combined treatment of pregabalin and memantine to decrease the pain and rate of gray matter atrophy associated with FMS. This dual-drug therapy targets the voltage-gated calcium ion channel (VGCC) and the N-methyl d-aspartate receptor (NMDAR) (respectively), two primary components of the human nociceptive and pain processing systems.

Co-occurrence and associations of pain and fatigue in a community sample of Dutch adults

Widespread pain and chronic fatigue are common in the general population. Previous research has demonstrated co-occurrence of syndromes that are associated with pain and fatigue (fibromyalgia and chronic fatigue syndrome), but there is limited existing data on the co-occurrence of these symptoms in general. This study investigates the co-occurrence of pain and fatigue, and characterises people with these symptoms individually, and in combination. A postal questionnaire was sent to a random sample of 4741 community dwelling Dutch adults registered with five general practices. There were 2447 participants (adjusted response=53.5%). Persistent fatigue was reported by 60% of the 451 subjects with chronic widespread pain. Chronic widespread pain was reported by 33% of the 809 responders with persistent fatigue. Anxiety and depression were more common in subjects who reported both symptoms than those who reported either one or neither. Participants who had chronic disease, high body mass index, low activity levels or did not perceive ability to influence health had higher adjusted odds of reporting both symptoms (but not one alone) than subjects not having these characteristics. Pain and fatigue occur more often than would be expected by chance and there are a number of reasons for this. Clinicians should be aware that co-occurrence of the symptoms is common, especially in people who have high BMI or chronic disease, and that people with both symptoms are often anxious or depressed. Further work should address longitudinal associations of pain and fatigue.

Customizing treatment of chronic fatigue syndrome and fibromyalgia: the role of perpetuating factors

BACKGROUND

Syndromes characterized by chronic, medically unexplained fatigue, effort- and stress-intolerance, and widespread pain are highly prevalent in medicine.

RESULTS

In chronic fatigue syndrome (CFS) and fibromyalgia (FM), various perpetuating factors may impair patients' quality of life and functioning and impede recovery. Although cognitive-behavioral and graded-exercise therapy are evidence-based treatments, the effectiveness and acceptability of therapeutic interventions in CFS/FM may largely depend on a customized approach taking the heterogeneity of perpetuating factors into account.

CONCLUSION

Further research should clarify the aim and outcome of different treatment strategies in CFS/FM, as well as the underlying mechanisms of change, including those facilitating neurobiological recovery.

Modulation of antigen-induced chronic fatigue in mouse model of water immersion stress by naringin, a polyphenolic antioxidant

It is believed that physical stress, infection and oxidative stress are involved in the development of chronic fatigue syndrome. There is little evidence stating the beneficial role of nutritional supplements in chronic fatigue syndrome. Based on this, this study was designed to evaluate the effect of naringin, a natural polyphenol, in a mouse model of immunologically-induced fatigue, wherein purified lipopolysaccharide (LPS) as well as Brucella abortus (BA) antigen was used as immunogens. The assessment of chronic fatigue syndrome was based on chronic water-immersion stress test for 10 mins as well as measurement of hyperalgesia for 19 days. Immobility time and tail withdrawal latency as well as oxidative stress were taken as the markers of fatigue. Mice challenged with LPS or BA for 19 days showed significant increase in the immobility time, hyperalgesia and oxidative stress on 19th day. Serum tumor necrosis factor-alpha (TNF-alpha) levels markedly increased with LPS or BA challenge. Concurrent treatment with naringin resulted in the significant decrease in the immobility time as well as hyperalgesia. There was significant attenuation of oxidative stress as well as in TNF-alpha levels. Present findings strongly suggest the role of oxidative stress and immunological activation in the pathophysiology of chronic fatigue syndrome, and treatment with naringin can be a valuable option in chronic fatigue syndrome.

Effect of Static and Dynamic Heat Pain Stimulus Profiles on the Temporal Dynamics and Interdependence of Pain Qualities, Intensity, and Affect

Acute and chronic pains are characterized by a particular constellation of pain qualities, such as burning, aching, stinging, or sharp feelings. However, the temporal pattern of specific pain qualities and their relationship with pain and affect is not well understood. In addition, little is known about how the temperature time course of the stimulus impacts the temporal dynamics of pain qualities and the relationship between pain qualities. Therefore we applied two types of stimuli to the feet of 16 healthy subjects, each calibrated to evoke a similar pain magnitude (50/100): static stimulus held at constant intensity and dynamic stimulus increased in intensity in small steps. Stimulus runs consisted of three 30-s stimuli (either static or dynamic) with an interstimulus interval of 60 s. Continuous on-line ratings of pain, burning, sharp, stinging, cutting, and annoyance were obtained in separate runs, and the evoked responses were characterized by within-stimulus adaptation (early: 0- to 15-s peak vs. late: 25- to 40-s peak) and by their temporal properties (time to onset, peak, and end). The temporal profile of the burning sensation was similar to the pain and annoyance evoked by the static and dynamic stimuli. However, the sharp, stinging and cutting sensations attenuated in response to the static stimuli ( P < 0.01) but intensified along with pain and affect in response to the dynamic stimuli ( P < 0.05), whereas there was no attenuation in the evoked profiles of pain ( P = 0.61), annoyance ( P = 0.27), or burning quality ( P = 0.27). These data demonstrate that specific pain qualities with known differences in underlying mechanisms have distinct temporal dynamics that depend on the stimulus intensity dynamics.