Contribution of the local and referred pain from active myofascial trigger points in fibromyalgia syndrome

A Bibliometric Analysis of Acupuncture Therapy in the Treatment of Musculoskeletal Pain from 2003 to 2022

Background

Acupuncture therapy has been widely used in the treatment of musculoskeletal pain (MP) in many countries around the world. However, there are no bibliometric studies on acupuncture therapy for MP. Therefore, the aim of this study was to analyze the current status, frontiers and hot spots in the use of acupuncture therapy for the treatment of MP.

Methods

Literature on acupuncture therapy for MP was extracted from the Web of Science Core Collection database from 2003 to 2022. CiteSpace 6.2.R4 (64-bit) software was used to analyze the number and centrality of journals, countries, institutions, authors, references and keywords, and the functions of co-occurrence and clustering were applied to draw a visual knowledge map.

Results

Over the past 20 years, the annual journal publications have been on a steady upward trend, with 438 articles published in 143 journals, including Acupuncture in Medicine Journal published the most (28, 6.39%), JAMA-Journal of the American Medical Association was the journal with the highest impact factor (IF = 120.7003), USA dominated with the most publications (140, 31.96%) among 44 countries, and among 196 research organizations Kyung Hee University was the most prolific (19, 4.34%) and Ha, In-Hyuk was the most published author (9, 2.05%). "Acupuncture" is the most popular and highly sought after keywords. "Low back pain" is the keyword with the highest centrality.

Conclusion

This article provides the current situation of the use of acupuncture therapy in the treatment of MP in the past 20 years, and statistical analysis reveals that "low back pain", "knit osteoporosis" and "break cancer" are new research diseases related to acupuncture therapy for MP, and "myobasic trigger point" is a new research direction of acupuncture therapy for MP. Therefore, this study helps researchers grasp the research hotspots and provide certain references for in-depth research and future topic selection.

Myofascial Pain Syndrome in Women with Primary Dysmenorrhea: A Case-Control Study

There is limited information on myofascial trigger points (MTrPs) and specific symptoms of chronic pelvic pain and, more specifically, dysmenorrhea. The objective of this study was to determine whether patients suffering from primary dysmenorrhea present alterations in mechanosensitivity and pain patterns, and greater presence of MTrPs in the abdominal and pelvic floor muscles. A case-control study was carried out with a total sample of 84 participants distributed based on primary dysmenorrhea and contraceptive treatment. The sample was divided into four groups each comprising 21 women. Data on pain, quality of life, and productivity and work absenteeism were collected; three assessments were made in different phases of the menstrual cycle, to report data on pressure pain threshold, MTrP presence, and referred pain areas. One-way ANOVA tests showed statistically significant differences (p < 0.01) between the groups, for the Physical Health domain and the total score of the SF-12 questionnaire, and for all the domains of the McGill questionnaire; but no significant differences were found in the data from the WPAI-GH questionnaire. Statistically significant data (p < 0.01) were found for mechanosensitivity in the abdominal area and limbs, but not for the lumbar assessment, within the group, with very few significant intergroup differences. The frequency of active MTrPs is higher in the groups of women with primary dysmenorrhea and during the menstrual phase, with the prevalence of myofascial trigger points of the iliococcygeus muscle being especially high in all examination groups (>50%) and higher than 70% in women with primary dysmenorrhea, in the menstrual phase, and the internal obturator muscle (100%) in the menstrual phase. Referred pain areas of the pelvic floor muscles increase in women with primary dysmenorrhea.

Current Concept of Quantitative Sensory Testing and Pressure Pain Threshold in Neck/Shoulder and Low Back Pain

In recent years, several published articles have shown that quantitative sensory testing (QST) and pressure pain threshold (PPT) are useful in the analysis of neck/shoulder and low back pain. A valid reference for normal PPT values might be helpful for the clinical diagnosis of abnormal tenderness or muscle pain. However, there have been no reliable references for PPT values of neck/shoulder and back pain because the data vary depending on the devices used, the measurement units, and the area examined. In this article, we review previously published PPT articles on neck/shoulder and low back pain, discuss the measurement properties of PPT, and summarize the current data on PPT values in patients with chronic pain and healthy volunteers. We also reveal previous issues related to PPT evaluation and discuss the future of PPT assessment for widespread use in general clinics. We outline QST and PPT measurements and what kinds of perceptions can be quantified with the PPT. Ninety-seven articles were selected in the present review, in which we focused on the normative values and abnormal values in volunteers/patients with neck/shoulder and low back pain. We conducted our search of articles using PubMed and Medline, a medical database. We used a combination of “Pressure pain threshold” and “Neck shoulder pain” or “Back pain” as search terms and searched articles from 1 January 2000 to 1 June 2022. From the data extracted, we revealed the PPT values in healthy control subjects and patients with neck/shoulder and low back pain. This database could serve as a benchmark for future research with pressure algometers for the wide use of PPT assessment in clinics.

Effect of central sensitization inventory on the number of painful sites and pain severity in a Japanese regional population cohort

BACKGROUND

To investigate the association between the central sensitization inventory (CSI), a screening tool for central sensitization, and the number of painful sites and the severity of pain in locomotive organs in an epidemiological study in the elderly.

METHODS

A total of 379 individuals who underwent musculoskeletal disease screening were enrolled in this study. The CSI was used to assess symptoms of central sensitization. The number and location of painful sites and the severity of pain were evaluated using pain mapping and a numerical rating scale (NRS) at 37 sites. We investigated the association between the number of painful sites and CSI score, and the association between the severity of low back pain or knee pain and CSI score.

RESULTS

There was a positive correlation between CSI score and the number of painful sites. The CSI score was significantly higher in those with significant low back pain than in those without pain, and the high-CSI group tended to have a greater number of painful sites. Comparison of CSI scores between participants with low back pain alone and those with low back pain and posterior lower leg pain showed that the latter group had a significantly higher CSI score than the former group. The CSI score in participants with radiographic evidence of knee osteoarthritis was significantly higher in those with knee pain than in those without pain.

CONCLUSIONS

The results of this study suggest that participants with significant low back pain and a higher number of painful sites are more susceptible to the influence of central sensitization. In addition, CSI score was higher in participants with low back pain and posterior lower leg pain than in those with low back pain alone, suggesting that the spread of pain may be due to central sensitization.

Advances in the management of fibromyalgia: what is the state of the art?

INTRODUCTION

Fibromyalgia (FM) is a chronic pain syndrome associated with fatigue, insomnia, dyscognition, and emotional distress. Critical illness mechanisms include central sensitization to nociceptive and non-nociceptive stimuli often resulting in hypersensitivity to all sensory input.

AREAS COVERED

The clinical presentation of FM can vary widely and therefore requires therapies tailored to each patient's set of symptoms. This manuscript examines currently prescribed therapeutic approaches supported by empirical evidence as well as promising novel treatments. Although pharmacological therapy until now has been only moderately effective for FM symptoms, it represents a critical component of every treatment plan.

EXPERT OPINION

Currently approved pharmacological therapies for FM symptoms have limited but proven effectiveness. Novel therapies with cannabinoids and naltrexone appear promising. Recent functional imaging studies of FM have discovered multiple brain network abnormalities that may provide novel targets for mechanism-based therapies. Future treatment approaches, however, need to improve more than clinical pain but also other FM domains like fatigue, insomnia, and distress.

Intramuscular Innervation of the Supraspinatus Muscle Assessed Using Sihler’s Staining: Potential Application in Myofascial Pain Syndrome

Despite the positive effects of botulinum neurotoxin (BoNT) injection into the neural arborized area, there is no anatomical evidence in the literature regarding the neural arborization of the supraspinatus muscle. The present study aimed to define the intramuscular neural arborized pattern of the supraspinatus muscle using the modified Sihler’s staining method to facilitate the establishment of safe and effective injection sites in patients with myofascial pain in the supraspinatus muscle. Seventeen supraspinatus muscles from 15 embalmed cadavers were dissected. Precise suprascapular nerve entry locations were also observed. Intramuscular neural arborization was visualized by Sihler’s staining. The supraspinatus muscle was divided into four portions named A, B, C, and D. The nerve entry points were observed in 88.2% (15 of 17 cases) of section B and 76.5% (13 of 17 cases) of section C of the supraspinatus muscle, respectively. The concentration of intramuscular neural arborization was highest in section B of the supraspinatus muscle, which was the center of the supraspinatus muscle. When the clinician performs a trigger point and a BoNT injection into the supraspinatus muscle, injection within the medial 25–75% of the supraspinatus muscle will lead to optimal results when using small amounts of BoNT and prevent undesirable paralysis.

MATLAB Analysis of SP Test Results—An Unusual Parasympathetic Nervous System Activity in Low Back Leg Pain: A Case Report

The Skorupska Protocol (SP) test is a new validated tool used to confirm nociplastic pain related to muscles based on a pathological autonomic nervous system (ANS) activity due to muscle nociceptive noxious stimulation analyzed automatically. Two types of amplified vasomotor response are defined as possible: vasodilatation and vasoconstriction. Until now, amplified vasodilatation among low back leg pain and/or sciatica subjects in response to the SP test was confirmed. This case report presents an unusual vasomotor response to the SP test within the pain zone of a sciatica-like case. Conducted twice, the SP test confirmed amplified vasoconstriction within the daily complaint due to noxiously stimulated muscle-referred pain for the first time. Additionally, a new type of the SP test analysis using MATLAB was presented. The SP test supported by MATLAB seems to be an interesting solution to confirm nociplastic pain related to muscles based on the pathological autonomic reactivity within the lower leg back pain zone. Further studies using the SP test supported by MATLAB are necessary to compare the SP test results with the clinical state and other types of nociplastic pain examination.

Differential sensory and clinical phenotypes of patients with chronic widespread and regional musculoskeletal pain

The differentiation of chronic primary pain syndromes into those with widespread vs regional musculoskeletal pain has been characterized by controversial discussions about common or distinct mechanisms and core clinical and sensory criteria. For example, the recent revision of fibromyalgia criteria has discarded sensory characteristics such as number of "tender points." This study examined empirical evidence related to this diagnostic shift and aimed to identify basic sensory-clinical pain phenotypes in patients with chronic local primary pain (chronic primary back pain [CBP]) and patients with chronic widespread primary pain (fibromyalgia syndrome). Combined sensory-clinical pain phenotypes of 185 patients with previous CBP and fibromyalgia syndrome diagnoses were derived by a stepwise data reduction through descriptive statistical, correlational, principal components and latent class analyses. Clusters were cross-validated by linear discriminant analysis. Four clusters of patients were identified, requiring 4 pressure pain sensitivity markers (number of sensitive tender and control points, pain intensity, and pressure pain threshold at the trapezius) and 2 clinical pain characteristics (pain regions and present pain intensity). Subsequent discriminant analysis revealed that 3 discriminant functions of pressure sensitivity markers sufficed to differentiate the clusters. These sensory-clinical phenotypes differed also in somatic symptoms and impairment but neither in psychopathology nor in psychosocial cofactors. The results highlight the relevance of sensory testing in combination with clinical pain assessment in chronic primary pain syndromes.

Spinal accessory neuropathy in patients with chronic trapezius myofascial pain syndrome

Background

Myofascial pain syndrome is a common musculoskeletal problem affecting the trapezius muscle. The aim was to assess the presence of spinal accessory neuropathy in patients with unilateral chronic trapezius myofascial pain syndrome.

Results

The study included 25 patients with unilateral chronic trapezius myofascial pain syndrome and 20 apparently healthy volunteers as the control group. There was a significantly delayed spinal accessory nerve latency on the symptomatic side in comparison to either asymptomatic side (P = 0.014) and control group (P = 0.001). Compound muscle action potential amplitude did not significantly differ between the symptomatic side versus the asymptomatic side and control group. Delayed spinal accessory nerve latency was present in seven patients (28%) and reduced compound muscle action potential amplitude in one of them (4%). The needle electromyography of the upper trapezius muscle revealed neuropathic motor units and incomplete interference pattern in the patient who showed reduced compound muscle action potential amplitude. Abnormal rest potentials were absent in all patients. Individually, seven patients (28%) had electrophysiological evidence of spinal accessory neuropathy, but only one (4%) of them had clinical evidence of spinal accessory neuropathy. Patients with abnormal electrophysiological findings had longer duration of complaint and more severe pain.

Conclusions

Spinal accessory neuropathy is common among patients with chronic trapezius myofascial pain syndrome. It could contribute to increased pain severity of myofascial pain syndrome. Electrodiagnosis is a good modality for identifying subclinical spinal accessory neuropathy.

Quality and readability of online information on myofascial pain syndrome

INTRODUCTION

The reliability of the information on the Internet, which people use as an easy and practical solution about diseases, is essential for public health. Our aim in this study is to evaluate the quality and readability of websites related to myofascial pain syndrome.

METHODS

On April 4, 2020, websites were searched on the Google search engine using the term "myofascial pain syndrome". The typologies, quality, readability, and content parameters of the sites were analyzed. Websites were divided into eight categories according to typology. To evaluate the quality, we evaluated the websites according to the JAMA scoring system or a HONcode certificate existence. Flesch-Kincaid grade and the Simple Measure of Gobbledygook was used to evaluate readability. Content analysis was performed for etiology, symptoms, diagnosis, and treatment.

RESULTS

56 of the 151 websites evaluated were classified as high-quality websites. It was determined that the quality scores of scientific publications and professional websites were high. Comparing the readability parameters of the websites in terms of quality, there was no significant difference between high-quality websites and low-quality websites (p = 0.391 and 0.746 respectively). The content was focused on etiology on scientific websites, while on commercial and professional websites, the content was focused on treatment.

CONCLUSION

High-quality websites did not offer an advantage in readability parameters. These results show that online information about MPS should be questioned and more extensive studies are required.

Novel application of dry needling for neuropathic myofascial ankle pain and dysfunction following insidious integumentary infection: A case report

BACKGROUND

Dry needling (DN) was effectively applied to a patient whose primary complaint was hyperalgesia and decreased ankle function meeting criteria for neuropathic myofascial pain following an integumentary infection, skin grafting and immobilization.

CASE DESCRIPTION

A 33-year-old male serving on active duty in the United States Air Force was referred to physical therapy for decreased ankle range of motion and pain, eight weeks after an integumentary infection on his ankle. The infection was complicated by tissue loss requiring skin grafting for closure. Two months of traditional rehabilitation was unsuccessful and this patient was referred for DN treatment.

OUTCOMES

Clinically relevant improvements were achieved after one treatment. After 48 hours, the patient's reported Pain Quality Assessment Scale (PQAS) dropped from a baseline 67 to 34 and Lower Extremity Functional Scale (LEFS) increased from 44 to 56. Plantarflexion and dorsiflexion improved by 15° and inversion and eversion by five degrees. After one year and 11 DN treatments, function continued to improve as demonstrated by single leg stance time improvement from 4 s to more than 60 seconds, without pain, a final LEFS of 72 and a return to unrestricted full duty.

CONCLUSION

DN is an increasingly utilized treatment option for myofascial pain. This case report represents a unique application of DN to an atypical patient presenting with neuropathic myofascial pain syndrome that demonstrated improvement with DN as the sole intervention. Further research regarding the application of DN as a treatment option for neuropathic myofascial pain syndromes is needed.

Do Nutritional Factors Interact with Chronic Musculoskeletal Pain? A Systematic Review

Dietary patterns may play an important role in musculoskeletal well-being. However, the link between dietary patterns, the components of patients' diet, and chronic musculoskeletal pain remains unclear. Therefore, the purpose of this review was to systematically review the literature on the link between dietary patterns, the components of patients' diet and chronic musculoskeletal pain. This review was conducted following the "Preferred Reporting Items for Systematic reviews and Meta-Analyses" (PRISMA) guidelines and was registered in PROSPERO with the registration number CRD42018110782. PubMed, Web of Science, and Embase online databases were searched. After screening titles and abstracts of 20,316 articles and full texts of 347 articles, 12 eligible articles were included in this review, consisting of nine experimental and three observational studies. Seven out of nine experimental studies reported a pain-relieving effect of dietary changes. Additionally, protein, fat, and sugar intake were found to be associated with pain intensity and pain threshold. In conclusion, plant-based diets might have pain relieving effects on chronic musculoskeletal pain. Patients with chronic rheumatoid arthritis pain can show inadequate intake of calcium, folate, zinc, magnesium, and vitamin B6, whilst patients with fibromyalgia can show a lower intake of carbohydrates, proteins, lipids, vitamin A-E-K, folate, selenium, and zinc. Chronic pain severity also shows a positive relation with fat and sugar intake in osteoarthritis, and pain threshold shows a positive association with protein intake in fibromyalgia.

Benefits of dry needling of myofascial trigger points on autonomic function and photoelectric plethysmography in patients with fibromyalgia syndrome

Background:

Fibromyalgia syndrome (FMS) is a condition characterised by the presence of chronic, widespread musculoskeletal pain, low pain threshold and hyperalgesia. Myofascial trigger points (MTrPs) may worsen symptoms in patients with FMS.

Objective:

The purpose of this randomised controlled trial was to compare the effects of dry needling and transcutaneous electrical nerve stimulation (TENS) on pain intensity, heart rate variability, galvanic response and oxygen saturation (SpO2).

Methods:

74 subjects with FMS were recruited and randomly assigned to either the dry needling group or the TENS group. Outcomes measures (pain intensity, heart rate variability, galvanic skin response, SpO2 and photoplethysmography) were evaluated at baseline and after 6 weeks of treatment. 2×2 mixed-model analyses of variance (ANOVAs) were performed.

Results:

The mixed-model ANOVAs showed significant differences between groups for the sensory dimension of pain, affective dimension of pain, total dimension of pain, visual analogue scale (VAS) and present pain intensity (PPI) (P=0.001). ANOVAs also showed that significant differences between groups were achieved for very low frequency power of heart rate variability (P=0.008) and low frequency power (P=0.033). There were no significant differences in dry needling versus TENS groups on the spectral analysis of the photoplethysmography and SpO2.

Conclusions:

This trial showed that application of dry needling therapy and TENS reduced pain attributable to MTrPs in patients with FMS, with greater improvements reported in the dry needling group across all dimensions of pain. Additionally, there were between-intervention differences for several parameters of heart rate variability and galvanic skin responses.

Trial registration number:

NCT02393352

Effect of Local Anesthetic Versus Botulinum Toxin-A Injections for Myofascial Pain Disorders: A Systematic Review and Meta-Analysis

OBJECTIVE

Myofascial pain is a chronic pain disorder characterized by the presence of painful localized regions of stiff muscle and/or myofascial trigger points. Intramuscular myofascial trigger point injections are considered first-line treatments for myofascial pain. Common injectates include local anesthetics and botulinum toxin-A (BTX-A). The objective of this systematic review was to compare the effectiveness of local anesthetics and BTX-A on pain intensity in patients with myofascial pain.

METHODS

A comprehensive systematic search of 3 databases, EMBASE, CENTRAL, and Medline was conducted. The search was comprised of words to describe "myofascial pain" and "injections." We performed a meta-analysis comparing local anesthetic and BTX-A injections across these follow-up week periods: 0 (immediately following the injection), 1 to 2, 3 to 4, 5 to 6, 7 to 8, 9 to 10, 11 to 12, 16, 18, 24 weeks with local anesthetics and BTX-A as subgroups. We also performed subgroup analyses comparing the effectiveness of local anesthetic injections and BTX-A injections at various muscle locations and comparing the effectives of single versus multiple injection sessions.

RESULTS

In total, 33 studies were included. A qualitative analysis suggested that local anesthetics and BTX-A were inconsistently effective at mitigating pain across all follow-up periods. The meta-analyses revealed that local anesthetic injections were more effective than BTX-A at mitigating pain intensity. Multiple injection sessions of local anesthetics were more beneficial than a single session.

CONCLUSIONS

Additional studies are needed to determine sources of heterogeneity mediating the observed differences in effectiveness of local anesthetic and BTX-A injections among the studies. Additional replicative studies are also needed to delineate the relative efficacy and effectiveness of local anesthetic and BTX-A injection. The quantitative results of this study suggest that patients overall experience more pain relief with local anesthetic injections.

Hyperexcitability to Electrical Stimulation and Accelerated Muscle Fatiguability of Taut Bands in Rats

Objective

Myofascial trigger points contribute significantly to musculoskeletal pain and motor dysfunction and may be associated with accelerated muscle fatiguability. The aim of this study was to investigate the electrically induced force and fatigue characteristics of muscle taut bands in rats.

Methods

Muscle taut bands were dissected out and subjected to trains of electrical stimulation. The electrical threshold intensity for muscle contraction and maximum contraction force (MCF), electrical intensity dependent fatigue and electrical frequency dependent fatigue characteristics were assessed in three different sessions (n=10 each) and compared with non-taut bands in the biceps femoris muscle.

Results

The threshold intensity for muscle contraction and MCF at the 10th, 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those of non-taut bands (all p<0.05). The MCF at the 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those at the 1st and 5th stimuli (all p<0.01). The MCF in the frequency dependent fatigue test was significantly higher and the stimulus frequency that induced MCF was significantly lower for taut bands than for non-taut bands (both p<0.01).

Conclusions

The present study demonstrates that the muscle taut band itself was more excitable to electrical stimulation and significantly less fatigue resistant than normal muscle fibres.

Effects of Chronic Musculoskeletal Pain on Fertility Potential in Lean and Overweight Male Patients

Both chronic pain and obesity are known to affect reproductive hormone profiles in male patients. However, the effect of these conditions, alone or in combination, on male fertility potential has received less attention. 20 chronic musculoskeletal pain patients and 20 healthy controls were divided into lean and overweight subgroups according to their BMI. Current level of chronic pain (visual analogue scale) and pressure pain thresholds (PPTs) in 16 predefined sites, classically described and tested as painful points on the lower body, were measured. Levels of reproductive hormone and lipid profiles were assessed by ELISA. Sperm concentration and motility parameters were analyzed using a computer-aided sperm analysis system. Sperm concentration, progressive motility, and percentage of hyperactivated sperm were generally lower in the chronic pain patients in both lean and overweight groups. The overweight control and the lean chronic pain groups demonstrated a significantly lower percentage of progressively motile sperm compared with the lean control group, suggesting that musculoskeletal chronic pain may have a negative influence on sperm quality in lean patients. However, due to the potential great negative influence of obesity on the sperm parameters, it is difficult to propose if musculoskeletal chronic pain also influenced sperm quality in overweight patients. Further research in chronic pain patients is required to test this hypothesis.

Spotlight on topographical pressure pain sensitivity maps: a review

Mechanical hyperalgesia defined as decreased pressure pain thresholds (PPTs) is commonly associated with pain. In this narrative review, we report the current state of the art within topographical pressure sensitivity maps. Such maps are based on multiple PPT assessments. The PPTs are assessed by an a priori defined grid with special focus on both spatial and temporal summation issues. The grid covers the muscle or the body region of interest using absolute or relative values determined from anatomical landmarks or anthropometric values. The collected PPTs are interpolated by Shepard or Franke and Nielson interpolation methods to create topographical pressure sensitivity maps. This new imaging technique has proven to be valuable in various disciplines including exercise physiology, neurology, physical therapy, occupational medicine, oncology, orthopedics, and sport sciences. The reviewed papers have targeted different body regions like the scalp, low back, neck-shoulder, and upper and lower extremities. The maps have delineated spatial heterogeneity in the pressure pain sensitivity underlining the different extents of pressure pain hyperalgesia in both experimentally induced and disease-associated pain conditions. Furthermore, various intervention studies have proven the utility of topographical pressure pain sensitivity maps. Topographical pressure pain sensitivity maps have contributed to revealing the efficacy of therapeutic, ergonomic, or training interventions that aim at reducing pain.

Anatomical Basis of the Myofascial Trigger Points of the Gluteus Maximus Muscle

Myofascial pain syndrome is characterized by pain and limited range of motion in joints and caused by muscular contracture related to dysfunctional motor end plates and myofascial trigger points (MTrPs). We aimed to observe the anatomical correlation between the clinically described MTrPs and the entry point of the branches of the inferior gluteal nerve into the gluteus maximus muscle. We dissected twenty gluteus maximus muscles from 10 human adult cadavers (5 males and 5 females). We measured the muscles and compiled the distribution of the nerve branches into each of the quadrants of the muscle. Statistical analysis was performed by using Student's t-test and Kruskal-Wallis tests. Although no difference was observed either for muscle measurements or for distribution of nerve branching among the subjects, the topography of MTrPs matched the anatomical location of the entry points into the muscle. Thus, anatomical substract of the MTrPs may be useful for a better understanding of the physiopathology of these disorders and provide basis for their surgical and clinical treatment.

Concurrent validation of a pressure pain threshold scale for individuals with myofascial pain syndrome and fibromyalgia

Background

Manual pressure palpation is an examination technique used in the classification of myofascial pain syndrome (MPS) and fibromyalgia (FM). Currently, there are no validated systems for classifying results. A valid and reliable pressure pain threshold scale (PPTS) may provide a means for clinicians to grade, document, and report findings. The purpose of this investigation was to validate a PPTS in individuals diagnosed with MPS and FM. Intra-rater reliability, concurrent validity, minimum cut-off value, and patient responses were evaluated.

Methods

Eighty-four participants who met the inclusion criteria were placed into three groups of 28 (N = 84): MPS, FM, and asymptomatic controls. All participants underwent a two-part testing session using the American College of Rheumatology criteria for classifying FM. Part-1 consisted of manual palpation with a digital pressure sensor for pressure consistency and part 2 consisted of algometry. For each tender point (18 total), participants graded tenderness using the visual analog scale (VAS) while the examiner concurrently graded response using a five-point PPTS.

Results

The PPTS had good intra-rater reliability (ICC ≥ .88). A moderate to excellent relationship was found between the PPTS and VAS for all groups with the digital pressure sensor and algometer (ρ ≥ .61). A minimum cut-off value of 2 on the PPTS differentiated participants with MPS and FM from asymptomatic controls.

Discussion

The results provide preliminary evidence validating the PPTS for individuals with MPS and FM. Future research should further study the clinimetric properties of the PPTS with other chronic pain and orthopedic conditions.

Levels of Evidence

2c.

Clinical Trial Registration

ClinicalTrials.gov registration No. NCT02802202.

Corticospinal excitability as a biomarker of myofascial pain syndrome

INTRODUCTION

Myofascial pain syndrome (MPS) is a common chronic pain disorder that lacks effective diagnostic criteria. To better understand neurophysiological changes in chronic pain, several trials exploring corticospinal excitability in different populations of patients with chronic pain have been performed.

OBJECTIVES

In this systematic review, we aimed to investigate the current literature on MPS and intracortical disinhibition, by means of increased intracortical facilitation and decreased intracortical inhibition (ICI).

METHODS

We performed a search on PubMed to identify clinical trials on MPS and transcranial magnetic stimulation measurements. We then applied the Harford Hill criteria to the identified studies to assess the possible causal relationship between intracortical disinhibition measurements and MPS. Finally, we compared our findings on MPS with other chronic pain conditions.

RESULTS

Four studies assessing corticospinal excitability in patients with MPS were found. Although the amount of trials available is limited, all the reported studies indicated an increased intracortical disinhibition in patients with MPS. Importantly, these measurements were also correlated with psychological factors, such as pain catastrophism, or anxiety. However, based on the Harford Hill criteria, we could not assert a strong causal relationship between these markers and MPS. Although intracortical disinhibition has been consistently found in patients having MPS, this lack of cortical inhibition was not only observed in this specific chronic pain syndrome but also in fibromyalgia and neuropathic pain conditions.

CONCLUSION

Intracortical disinhibition seems to be a marker that has been consistently observed in MPS. Future prospective cohort studies could provide new insights in the development of neoplastic and maladaptive changes occurring in chronic pain syndromes and help the development of new therapeutic options.

The effects of local cold application on fibromyalgia pain

AIM

This study was conducted to evaluate the effects of local cold application on pain when applied to the trapezius muscles of patients with fibromyalgia.

METHOD

A one-group, pre-test/post-test, pre-experimental model was applied in this study, which was conducted with 55 fibromyalgia patients who presented to a rheumatology outpatient clinic. A 10-min cold application was administered to one trapezius muscle of each patient. The participants' pain was evaluated, in total, four times (before the cold application and 10 min, 1.5 h and 24 h after the cold application). The visual analogue scale (VAS) for pain was used to collect data for the study, and Friedman and Wilcoxon tests were used to assess the data.

RESULTS

The patients' pain mean score before (6.45, SD:1.27) the cold applications was found to be significantly higher than the scores noted 10 min (2.75, SD:1.73), 1.5 h (2.45, SD:1.29), and 24 h (3.36, SD:1.30) after the application (P < 0.001).

CONCLUSION

The study found that local cold applications performed on the trapezius muscles of patients with fibromyalgia significantly decreased their pain. With its discovery of a new method of pain control in fibromyalgia patients, this study will significantly contribute to science and will serve as a guide for pain management, especially in nursing practice. Further studies to evaluate the maximum effect duration and effect mechanisms of local cold applications to the trapezius muscles of FM patients are indicated.

Therapeutic effects of dry needling in patients with upper trapezius myofascial trigger points

BACKGROUND

Active myofascial trigger points (MTrPs) are major pain generators in myofascial pain syndrome. Dry needling (DN) is an effective method for the treatment of MTrPs.

OBJECTIVE

To assess the immediate neurophysiological and clinical effects of DN in patients with upper trapezius MTrPs.

METHODS

This was a prospective, clinical trial study of 20 patients with upper trapezius MTrPs and 20 healthy volunteers (matched for height, weight, body mass index and age), all of whom received one session of DN. Primary outcome measures were neuromuscular junction response (NMJR) and sympathetic skin response (SSR). Secondary outcomes were pain intensity (PI) and pressure pain threshold (PPT). Data were collected at baseline and immediately post-intervention.

RESULTS

At baseline, SSR amplitude was higher in patients versus healthy volunteers (p<0.003). With respect to NMJR, a clinically abnormal increment and normal reduction was observed in patients and healthy volunteers, respectively. Moreover, PPT of patients was less than healthy volunteers (p<0.0001). After DN, SSR amplitude decreased significantly in patients (p<0.01), but did not change in healthy volunteers. A clinically important reduction in the NMJR of patients and increment in healthy volunteers was demonstrated after DN. PPT increased after DN in patients, but decreased in healthy volunteers (p<0.0001). PI improved after DN in patients (p<0.001).

CONCLUSIONS

The results of this study showed that one session of DN targeting active MTrPs appears to reduce hyperactivity of the sympathetic nervous system and irritability of the motor endplate. DN seems effective at improving symptoms and deactivating active MTrPs, although further research is needed.

TRIAL REGISTRATION NUMBER

IRCT20130316128.

Motor Cortex Excitability and BDNF Levels in Chronic Musculoskeletal Pain According to Structural Pathology

The central sensitization syndrome (CSS) encompasses disorders with overlapping symptoms in a structural pathology spectrum ranging from persistent nociception [e.g., osteoarthritis (OA)] to an absence of tissue injuries such as the one presented in fibromyalgia (FM) and myofascial pain syndrome (MPS). First, we hypothesized that these syndromes present differences in their cortical excitability parameters assessed by transcranial magnetic stimulation (TMS), namely motor evoked potential (MEP), cortical silent period (CSP), short intracortical inhibition (SICI) and short intracortical facilitation (SICF). Second, considering that the presence of tissue injury could be detected by serum neurotrophins, we hypothesized that the spectrum of structural pathology (i.e., from persistent nociception like in OA, to the absence of tissue injury like in FM and MPS), could be detected by differential efficiency of their descending pain inhibitory system, as assessed by the conditioned pain modulation (CPM) paradigm. Third, we explored whether brain-derived neurotrophic factor (BDNF) had an influence on the relationship between motor cortex excitability and structural pathology. This cross-sectional study pooled baseline data from three randomized clinical trials. We included females (n = 114), aged 19-65 years old with disability by chronic pain syndromes (CPS): FM (n = 19), MPS (n = 54), OA (n = 27) and healthy subjects (n = 14). We assessed the serum BDNF, the motor cortex excitability by parameters the TMS measures and the change on numerical pain scale [NPS (0-10)] during CPM-task. The adjusted mean (SD) on the SICI observed in the absence of tissue injury was 56.36% lower than with persistent nociceptive input [0.31(0.18) vs. 0.55 (0.32)], respectively. The BDNF was inversely correlated with the SICI and with the change on NPS (0-10)during CPM-task. These findings suggest greater disinhibition in the motor cortex and the descending pain inhibitory system in FM and MPS than in OA and healthy subjects. Likewise, the inter-hemispheric disinhibition as well as the dysfunction in the descending pain modulatory system is higher in chronic pain without tissue injury compared to a structural lesion. In addition, they suggest that a greater level of serum BDNF may be involved in the processes that mediate the disinhibition of motor cortex excitability, as well as the function of descending inhibitory pain modulation system, independently of the physiopathology mechanism of musculoskeletal pain syndromes.

Myofascial pain and fibromyalgia: two different but overlapping disorders

There is good evidence supporting that people with fibromyalgia syndrome (FMS) exhibit central sensitization. The role of peripheral nociception is under debate in FMS. It seems that widespread pain experienced in FMS is considered multiple regional pains; therefore, several authors proposed that muscles play a relevant role in FMS. Trigger points (TrPs) have long been a contentious issue in relation to FMS. Preliminary evidence reported that the overall spontaneous pain is reproduced by referred pain from active TrPs, suggesting that FMS pain is largely composed of pain arising, at least partially, from TrPs. Finally, there is preliminary evidence suggesting that management of TrPs is able to modulate the CNS and is effective for reducing pain in FMS, although results are conflicting and future studies are clearly needed.

Signs and Symptoms of Myofascial Pain: An International Survey of Pain Management Providers and Proposed Preliminary Set of Diagnostic Criteria

OBJECTIVE

Myofascial Pain Syndrome (MPS) is highly prevalent in pain medicine, yet there is no "gold standard" or set of validated diagnostic criteria for clinical or research use. A survey collected clinician perspectives on MPS to foster the development of a formal case definition for empirical validation.

DESIGN

International survey.

METHODS

Clinician members of the International Association for the Study of Pain and the American Academy of Pain Medicine received a survey of the symptoms and signs of MPS and expected response to treatment. Write-in fields were available for each category and to suggest relevant diagnostic studies.

RESULTS

Two hundred fourteen responses were received from 4,143 surveys mailed. The most essential components of MPS were tender spots that recreate symptoms when palpated. MPS was also associated with muscle stiffness, decreased range of motion of the affected joints, worsening symptoms with stress, palpable taut band or tender nodule, and referred pain with palpation of the tender spot. Diagnostic studies are reported to be useful for ruling out other pathology, but not to confirm the presence of the condition.

CONCLUSIONS

These results were used to propose a set of preliminary diagnostic criteria; expert consensus for case definition and subsequent empirical validation are required for standardization in research and clinical management of MPS.

Trigger points: an anatomical substratum

This study aimed to bring the trapezius muscle knowledge of the locations where the accessory nerve branches enter the muscle belly to reach the motor endplates and find myofascial trigger points (MTrPs). Although anatomoclinical correlations represent a major feature of MTrP, no previous reports describing the distribution of the accessory nerve branches and their anatomical relationship with MTrP are found in the literature. Both trapezius muscles from twelve adult cadavers were carefully dissected by the authors (anatomy professors and medical graduate students) to observe the exact point where the branches of the spinal accessory nerve entered the muscle belly. Dissection was performed through stratigraphic layers to preserve the motor innervation of the trapezius muscle, which is located deep in the muscle. Seven points are described, four of which are motor points: in all cases, these locations corresponded to clinically described MTrPs. The four points were common in these twelve cadavers. This type of clinical correlation between spinal accessory nerve branching and MTrP is useful to achieve a better understanding of the anatomical correlation of MTrP and the physiopathology of these disorders and may provide a scientific basis for their treatment, rendering useful additional information to therapists to achieve better diagnoses and improve therapeutic approaches.

A critical evaluation of Quintner et al: missing the point

The objective of this article is to critically analyze a recent publication by Quinter, Bove and Cohen, published in Rheumatology, about myofascial pain syndrome and trigger points (Quintner et al., 2014). The authors concluded that the leading trigger point hypothesis is flawed in reasoning and in science. They claimed to have refuted the trigger point hypothesis. The current paper demonstrates that the Quintner et al. paper is a biased review of the literature replete with unsupported opinions and accusations. In summary, Quintner et al. have not presented any convincing evidence to believe that the Integrated TrP Hypothesis should be laid to rest.

Effect of transcutaneous electrical nerve stimulation on pain, function, and quality of life in fibromyalgia: a double-blind randomized clinical trial

BACKGROUND

Fibromyalgia is a common chronic pain condition that has a significant impact on quality of life and often leads to disability. To date, there have been few well-controlled trials assessing the utility of nonpharmacological treatment modalities such as transcutaneous electrical nerve stimulation (TENS) in the management of pain and improvement in function in individuals with fibromyalgia.

OBJECTIVES

The purpose of this study will be to complete a long-term, multicenter study to assess the effects of TENS in women with fibromyalgia.

DESIGN

This will be a phase II randomized, double-blind, placebo-controlled, multicenter clinical trial.

PARTICIPANTS

Three hundred forty-three participants with fibromyalgia will be recruited for this study.

INTERVENTION

Participants will be randomly assigned to 1 of 3 groups: the intervention (TENS), placebo, or no treatment. After completing the randomized period, all participants will receive the intervention for 1 month. The participants will be asked to use TENS at the highest tolerable level for at least 2 hours daily during physical activity.

MEASUREMENTS

The primary outcome will be pain with movement, with secondary outcomes assessing functional abilities, patient-reported outcomes, and quantitative sensory testing.

LIMITATIONS

Because having participants refrain from their typical medications is not practical, their usage and any change in medication use will be recorded.

CONCLUSIONS

The results of this study will provide some of the first evidence from a large-scale, double-blind, placebo-controlled trial on the effectiveness of TENS on pain control and quality-of-life changes in patients with fibromyalgia.

Mechanistic experimental pain assessment in computer users with and without chronic musculoskeletal pain

Background

Musculoskeletal pain from the upper extremity and shoulder region is commonly reported by computer users. However, the functional status of central pain mechanisms, i.e., central sensitization and conditioned pain modulation (CPM), has not been investigated in this population. The aim was to evaluate sensitization and CPM in computer users with and without chronic musculoskeletal pain.

Methods

Pressure pain threshold (PPT) mapping in the neck-shoulder (15 points) and the elbow (12 points) was assessed together with PPT measurement at mid-point in the tibialis anterior (TA) muscle among 47 computer users with chronic pain in the upper extremity and/or neck-shoulder pain (pain group) and 17 pain-free computer users (control group). Induced pain intensities and profiles over time were recorded using a 0-10 cm electronic visual analogue scale (VAS) in response to different levels of pressure stimuli on the forearm with a new technique of dynamic pressure algometry. The efficiency of CPM was assessed using cuff-induced pain as conditioning pain stimulus and PPT at TA as test stimulus.

Results

The demographics, job seniority and number of working hours/week using a computer were similar between groups. The PPTs measured at all 15 points in the neck-shoulder region were not significantly different between groups. There were no significant differences between groups neither in PPTs nor pain intensity induced by dynamic pressure algometry. No significant difference in PPT was observed in TA between groups. During CPM, a significant increase in PPT at TA was observed in both groups (P < 0.05) without significant differences between groups. For the chronic pain group, higher clinical pain intensity, lower PPT values from the neck-shoulder and higher pain intensity evoked by the roller were all correlated with less efficient descending pain modulation (P < 0.05).

Conclusions

This suggests that the excitability of the central pain system is normal in a large group of computer users with low pain intensity chronic upper extremity and/or neck-shoulder pain and that increased excitability of the pain system cannot explain the reported pain. However, computer users with higher pain intensity and lower PPTs were found to have decreased efficiency in descending pain modulation.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-412) contains supplementary material, which is available to authorized users.

Management of fibromyalgia syndrome: review of evidence

Fibromyalgia syndrome (FMS) is a common chronic musculoskeletal pain disorder of unknown etiology and characterized by generalized body pain, hyperalgesia, and other functional and emotional comorbidities. Despite extensive research, no treatment modality is effective for all FMS patients. In this paper, we briefly review the history of FMS and diagnostic criteria, and potential pathophysiological mechanisms including central pain modulation, neurotransmitters, sympatho-adrenal and hypothalamic-pituitary-adrenal systems and peripheral muscle issues. The primary focus of the paper is to review treatment options for managing fibromyalgia symptoms. We will discuss FDA-approved medications and other pharmacologic agents, and non-pharmacologic treatments that have shown promising effects.

Safety and effectiveness of vibration massage by deep oscillations: a prospective observational study

The objective of this study is to assess the safety of treatment with vibration massage using a deep oscillation device and the effects on symptom severity and quality of life in patients with primary fibromyalgia syndrome (FMS). Outpatients with FMS performed an observational prospective study with visits 2-4 weeks after the last treatment (control) and after further 2 months (follow-up). Patients were treated with 10 sessions of 45 min deep oscillation massage, 2/week. Primary outcome parameters were safety and tolerability (5-level Likert scale (1 = very good)) (after each treatment session and at control visit). Secondary outcome parameters were symptom severity (Fibromyalgia Impact Questionnaire (FIQ), pain) and quality of life (SF-36). Seventy patients (97.1% females) were included. At control visit, 41 patients (58.6%) reported 63 mild and short-lasting adverse events, mainly worsening of prevalent symptoms such as pain and fatigue. Tolerability was rated as 1.8 (95% confidence interval: 1.53; 2.07). Symptoms and quality of life were significantly improved at both control and follow-up visits (at least P < 0.01). In conclusion, deep oscillation massage is safe and well tolerated in patients with FMS and might improve symptoms and quality of life rather sustained.

Trapezius activity of fibromyalgia patients is enhanced in stressful situations, but is similar to healthy controls in a quiet naturalistic setting: a case-control study

Background

Muscle activity and pain development of fibromyalgia (FM) patients in response to mental stress show inconsistent results, when compared to healthy controls (HCs). A possible reason for the inconsistent results is the large variation in stress exposures in different studies. This study compares muscle responses of FM patients and HCs for different modes and levels of imposed stress, to elucidate features in stress exposures that distinguish stress responses of FM patients from HCs.

Methods

Upper trapezius (clavicular and acromial fibers), deltoid, and biceps surface electromyographic (sEMG) activity was recorded in FM patients (n=26) and HCs (n=25). Heart rate (HR) was recorded and used as indicator of autonomic activation. Tests included inspiratory breath holding (sympathetic activation procedure), mental stress tests (color-word test and backward counting; 28 min), instructed rest prior to stress test (30 min TV watching), and controlled arm movement. sEMG and HR was also recorded during an unrestrained evening stay at a patient hotel. The 5-min period with lowest trapezius muscle activity was determined. Pain (shoulder/neck, low back pain) and perceived tension were scored on VAS scales at the start and the end of the stress test and at bedtime.

Results

Trapezius sEMG responses of FM patients were significantly higher than HCs during sympathetic activation, mental stress, and instructed rest, but similar during arm movement and unrestrained evening activity. HR of FM patients and HCs was similar during mental stress and in the evening, including the 5-min period with lowest trapezius activity. Muscle activity of FM patients during the stress test (with shoulder/neck pain development) and the evening stay (no pain development) was similar.

Conclusions

FM patients show elevated muscle activity (in particular trapezius activity) in situations with imposed stress, including sympathetic activation, and putative anticipatory stress. Muscle activity and HR were similar to HCs in instructed arm movement and in a situation approaching low-stress daily living. Pain development of FM patients during the stress test may be due to activation of several stress-associated physiological systems, and not obviously caused by muscle activity in isolation.

Dry needling - peripheral and central considerations

Dry needling is a common treatment technique in orthopedic manual physical therapy. Although various dry needling approaches exist, the more common and best supported approach targets myofascial trigger points. This article aims to place trigger point dry needling within the context of pain sciences. From a pain science perspective, trigger points are constant sources of peripheral nociceptive input leading to peripheral and central sensitization. Dry needling cannot only reverse some aspects of central sensitization, it reduces local and referred pain, improves range of motion and muscle activation pattern, and alters the chemical environment of trigger points. Trigger point dry needling should be based on a thorough understanding of the scientific background of trigger points, the differences and similarities between active and latent trigger points, motor adaptation, and central sensitize application. Several outcome studies are included, as well as comments on dry needling and acupuncture.

A Mechanism-Based Approach to Prevention of and Therapy for Fibromyalgia

Fibromyalgia syndrome (FMS) is characterized by pain referred to deep tissues. Diagnosis and treatment of FMS are complicated by a variable coexistence with regional pain, fatigue, sleep disruption, difficulty with mentation, and depression. The widespread, deep pain of FMS can be a consequence of chronic psychological stress with autonomic dysregulation. Stress acts centrally to facilitate pain and acts peripherally, via sympathetic vasoconstriction, to establish painful muscular ischemia. FMS pain, with or without a coexistent regional pain condition, is stressful, setting up a vicious circle of reciprocal interaction. Also, stress interacts reciprocally with systems of control over depression, mentation, and sleep, establishing FMS as a multiple-system disorder. Thus, stress and the ischemic pain it generates are fundamental to the multiple disorders of FMS, and a therapeutic procedure that attenuates stress and peripheral vasoconstriction should be highly beneficial for FMS. Physical exercise has been shown to counteract peripheral vasoconstriction and to attenuate stress, depression, and fatigue and improve mentation and sleep quality. Thus, exercise can interrupt the reciprocal interactions between psychological stress and each of the multiple-system disorders of FMS. The large literature supporting these conclusions indicates that exercise should be considered strongly as a first-line approach to FMS therapy.

Characteristics of referred muscle pain to the head from active trigger points in women with myofascial temporomandibular pain and fibromyalgia syndrome

Our aim was to compare the differences in the prevalence and the anatomical localization of referred pain areas of active trigger points (TrPs) between women with myofascial temporomandibular disorder (TMD) or fibromyalgia (FMS). Twenty women (age 46 ± 8 years) with TMD and 20 (age 48 ± 6 years) with FMS were recruited from specialized clinic. Bilateral temporalis, masseter, sternocleidomastoid, upper trapezius, and suboccipital muscles were examined for TrPs. TrPs were identified by palpation and considered active when the pain reproduced familiar pain symptom experienced by the patient. The referred pain areas were drawn on anatomical maps, digitalized and also measured. A new analysis technique based on a center of gravity (COG) method was used to quantitative estimate of the localization of the TrP referred pain areas. Women with FMS exhibited larger areas of usual pain symptoms than women with myofascial TMD (P < 0.001). The COG coordinates of the usual pain on the frontal and posterior pain maps were located more superior in TMD than in FMS. The number of active TrPs was significantly higher in TMD (mean ± SD 6 ± 1) than in FMS (4 ± 1) (P = 0.002). Women with TMD exhibited more active TrPs in the temporalis and masseter muscles than FMS (P < 0.01). Women with FMS had larger referred pain areas than those with TMD for sternocleidomastoid and suboccipital muscles (P < 0.001). Significant differences within COG coordinates of TrP referred pain areas were found in TMD, the referred pain was more pronounced in the orofacial region, whereas the referred pain in FMS was more pronounced in the cervical spine. This study showed that the referred pain elicited from active TrPs shared similar patterns as usual pain symptoms in women with TMD or FMS, but that distinct differences in TrP prevalence and location of the referred pain areas could be observed. Differences in location of referred pain areas may help clinicians to determine the most relevant TrPs for each pain syndrome in spite of overlaps in pain areas.

Muscle trigger points, pressure pain threshold, and cervical range of motion in patients with high level of disability related to acute whiplash injury

STUDY DESIGN

Cross sectional cohort study.

OBJECTIVE

To analyze the differences in the prevalence of trigger points (TrPs) between patients with acute whiplash-associated disorders (WADs) and healthy controls, and to determine if widespread pressure hypersensitivity and reduced cervical range of motion are related to the presence of TrPs in patients with acute WADs.

BACKGROUND

The relationship between active TrPs and central sensitization is not well understood in patients with acute WADs.

METHODS

Twenty individuals with a high level of disability related to acute WAD and 20 age- and sex-matched controls participated in the study. TrPs in the temporalis, masseter, upper trapezius, levator scapulae, sternocleidomastoid, suboccipital, and scalene muscles were examined. TrPs are defined as hypersensitive spots in a palpable taut band, producing a local twitch response and referred pain when palpated. Pressure pain threshold (PPT) was assessed bilaterally over the C5-6 zygapophyseal joints, second metacarpal, and tibialis anterior muscle. Active cervical range of motion, neck pain, and self-rated disability using the Neck Disability Index were also assessed.

RESULTS

The mean ± SD number of TrPs for the patients with acute WAD was 7.3 ± 2.8 (3.4 ± 2.7 were latent TrPs; 3.9 ± 2.5 were active TrPs). In comparison, healthy controls had 1.7 ± 2.2 latent and no active TrPs (P<0.01). In patients with acute WAD, the most prevalent sites for active TrPs were the levator scapulae and upper trapezius muscles. The number of active TrPs increased with higher neck pain intensity (P<0.001) and a higher number of days since the accident (P=.003). Patients had significantly lower PPTs in all tested locations and less active cervical range of motion than controls (P<.001). In the patient group, there were significant negative correlations between the number of active TrPs and PPT over the C5-C6 joints and cervical range of motion in flexion, extension, and rotation in both directions: the greater the number of active TrPs, the lower the bilateral PPT over the neck and the greater the cervical range of motion limitation.

CONCLUSIONS

The local and referred pain elicited from active TrPs reproduced neck and shoulder pain patterns in individuals with acute WADs with higher levels of disability. Patients with acute WADs exhibited widespread pressure hypersensitivity and reduced cervical mobility. The number of active TrPs was related to higher neck pain intensity, the number of days since the accident, higher pressure pain hypersensitivity over the cervical spine, and reduced active cervical range of motion.

Latent myofascial trigger points

A latent myofascial trigger point (MTP) is defined as a focus of hyperirritability in a muscle taut band that is clinically associated with local twitch response and tenderness and/or referred pain upon manual examination. Current evidence suggests that the temporal profile of the spontaneous electrical activity at an MTP is similar to focal muscle fiber contraction and/or muscle cramp potentials, which contribute significantly to the induction of local tenderness and pain and motor dysfunctions. This review highlights the potential mechanisms underlying the sensory-motor dysfunctions associated with latent MTPs and discusses the contribution of central sensitization associated with latent MTPs and the MTP network to the spatial propagation of pain and motor dysfunctions. Treating latent MTPs in patients with musculoskeletal pain may not only decrease pain sensitivity and improve motor functions, but also prevent latent MTPs from transforming into active MTPs, and hence, prevent the development of myofascial pain syndrome.

Spatial pain propagation over time following painful glutamate activation of latent myofascial trigger points in humans

The aim of this present study was to test the hypothesis that tonic nociceptive stimulation of latent myofascial trigger points (MTPs) may induce a spatially enlarged area of pressure pain hyperalgesia. Painful glutamate (.2 mL, 1M) stimulation of latent MTPs and non-MTPs in the forearm was achieved by an electromyography-guided procedure. Pain intensity (as rated on the visual analog scale [VAS]) and referred pain area following glutamate injections were recorded. Pressure pain threshold (PPT) was measured over 12 points in the forearm muscles and at the mid-point of tibialis anterior muscle before and at .5 hour, 1 hour, and 24 hours after glutamate injections. The results showed that maximal pain intensity, the area under the VAS curve, and referred pain area were significantly higher and larger following glutamate injection into latent MTPs than non-MTPs (all, P < .05). A significantly lower PPT level was detected over time after glutamate injection into latent MTPs at .5 hour (at 4 points), 1 hour (at 7 points), and 24 hours (at 6 points) in the forearm muscles. However, a significantly lower PPT was observed only at 24 hours after glutamate injection into non-MTPs in the forearm muscles (at 4 points, P < .05) when compared to the pre-injection PPT. PPT at the mid-point of the tibialis anterior was significantly decreased at 1 hour only as compared to the pre-injection PPT in both groups (< .05). The results of the present study indicate that nociceptive stimulation of latent MTPs is associated with an early onset of locally enlarged area of mechanical hyperalgesia.

PERSPECTIVE

This study shows that MTPs are associated with an early occurrence of a locally enlarged area of pressure hyperalgesia associated with spreading central sensitization. Inactivation of MTPs may prevent spatial pain propagation.

Myofascial pain syndromes and their evaluation

This article reviews the available published knowledge about the diagnosis, pathophysiology and treatment of myofascial pain syndromes from trigger points. Furthermore, epidemiologic data and clinical characteristics of these syndromes are described, including a detailed account of sensory changes that occur at both painful and nonpainful sites and their utility for diagnosis and differential diagnosis; the identification/diagnostic criteria available so far are critically reviewed. The key role played by myofascial trigger points as activating factors of pain symptoms in other algogenic conditions--headache, fibromyalgia and visceral disease--is also addressed. Current hypotheses on the pathophysiology of myofascial pain syndromes are presented, including mechanisms of formation and persistence of primary and secondary trigger points as well as mechanisms beyond referred pain and hyperalgesia from trigger points. Conventional and most recent therapeutic options for these syndromes are described, and their validity is discussed on the basis of results from clinical controlled studies.