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Background: Myofascial Pain Syndrome (MPS) is a common, overlooked, and underdiagnosed condition and has significant burden. MPS is often dismissed by clinicians while patients remain in pain for years. MPS can evolve into fibromyalgia, however, effective treatments for both are lacking due to absence of a clear mechanism. Many studies focus on central sensitization. Therefore, the purpose of this scoping review is to systematically search cross-disciplinary empirical studies of MPS, focusing on mechanical aspects, and suggest an organic mechanism explaining how it might evolve into fibromyalgia. Hopefully, it will advance our understanding of this disease., Methods: Systematically searched multiple phrases in MEDLINE, EMBASE, COCHRANE, PEDro, and medRxiv, majority with no time limit. Inclusion/exclusion based on title and abstract, then full text inspection. Additional literature added on relevant side topics. Review follows PRISMA-ScR guidelines. PROSPERO yet to adapt registration for scoping reviews., Findings: 799 records included. Fascia can adapt to various states by reversibly changing biomechanical and physical properties. Trigger points, tension, and pain are a hallmark of MPS. Myofibroblasts play a role in sustained myofascial tension. Tension can propagate in fascia, possibly supporting a tensegrity framework. Movement and mechanical interventions treat and prevent MPS, while living sedentarily predisposes to MPS and recurrence., Conclusions: MPS can be seen as a pathological state of imbalance in a natural process; manifesting from the inherent properties of the fascia, triggered by a disrupted biomechanical interplay. MPS might evolve into fibromyalgia through deranged myofibroblasts in connective tissue ("fascial armoring"). Movement is an underemployed requisite in modern lifestyle. Lifestyle is linked to pain and suffering. The mechanism of needling is suggested to be more mechanical than currently thought. A "global percutaneous needle fasciotomy" that respects tensegrity principles may treat MPS/fibromyalgia more effectively. "Functional-somatic syndromes" can be seen as one entity (myofibroblast-generated-tensegrity-tension), sharing a common rheuma-psycho-neurological mechanism., Competing Interests: The author has declared that no competing interests exist.

Purpose: This study aimed to identify the effects of myofascial pain syndrome on shoulder pain, range of motion, and body composition around the shoulder in middle-aged women., Methods: A total of 72 women participated in the randomized controlled trial. The subjects were grouped into an experimental group (n=39) and a control group (n=33). The experimental group received a resistance exercise program using an elastic band for 8 weeks, 3 days a week. The control group followed a normal daily for 8 weeks. Measurements were conducted three times; before the experimental treatment (pre-test), the 2nd and 8th weeks after treatment., Results: Regarding the general characteristics and homogeneity of the dependent variables, there were no significant differences between the two groups, except for the thickness of the left and right muscles and the left fat. After treatment, shoulder pain was significantly different between the two groups (F=18.54, p <.001) and the range of shoulder motion was significantly different (left, F=86.70, p <.001; right, F=98.66, p <.001). Furthermore, there were a significant differences in the thickness of muscles between the two groups (left, F=40.20, p <.001; right, F=29.57, p <.001); however, the thickness of fat was not significantly different., Conclusion: The resistance exercise program reduces shoulder pain and improves the range of motion of the shoulder joint and increases muscle mass on around the shoulder. It suggests to conduct a study to confirm the long-term exercise effect., Competing Interests: The authors declared no conflict of interest., (© 2020 Korean Society of Nursing Science.)

Background: Myofascial pain syndrome (MPS) is an important clinical condition that is characterized by chronic muscle pain and a myofascial trigger point (MTrP) located in a taut band (TB). Previous studies showed that EphrinB1 was involved in the regulation of pathological pain via EphB1 signalling, but whether EphrinB1-EphB1 plays a role in MTrP is not clear., Methods: The present study analysed the levels of p-EphB1/p-EphB2/p-EphB3 in biopsies of MTrPs in the trapezius muscle of 11 MPS patients and seven healthy controls using a protein microarray kit. EphrinB1-Fc was injected intramuscularly to detect EphrinB1s/EphB1s signalling in peripheral sensitization. We applied a blunt strike to the left gastrocnemius muscles (GM) and eccentric exercise for 8 weeks with 4 weeks of recovery to analyse the function of EphrinB1/EphB1 in the muscle pain model., Results: P-EphB1, p-EphB2, and p-EphB3 expression was highly increased in human muscles with MTrPs compared to healthy muscle. EphB1 (r = 0.723, n = 11, P < 0.05), EphB2 (r = 0.610, n = 11, P < 0.05), and EphB3 levels (r = 0.670, n = 11, P < 0.05) in the MPS group were significantly correlated with the numerical rating scale (NRS) in the MTrPs. Intramuscular injection of EphrinB1-Fc produces hyperalgesia, which can be partially prevented by pre-treatment with EphB1-Fc. The p-EphB1 contents in MTrPs of MPS animals were significantly higher than that among control animals (P < 0.01). Intramuscular administration of the EphB1 inhibitor EphB1-Fr significantly suppressed mechanical hyperalgesia., Conclusions: The present study showed that the increased expression of p-EphB1/p-EphB2/p-EphB3 was related to MTrPs in patients with MPS. This report is the first study to examine the function of EphrinB1-EphB1 signalling in primary muscle afferent neurons in MPS patients and a rat animal model. This pathway may be one of the most important and promising targets for MPS.

The purpose of this study was to investigate whether the ERK signaling pathway was involved in ameliorating chronic myofascial hyperalgesia from contused gastrocnemius muscle in rats. We established an animal model associated with myofascial pain syndrome and described the mechanism of muscle pain in an animal model. Changes in the mechanical pain threshold were observed 0.5, 1, 2, 3, 4, 5, 8, 12, 18, and 24 h after ERK inhibitor injection around myofascial trigger points (MTrPs) of the gastrocnemius muscle in rats. Morphological changes in gastrocnemius muscle cells were observed by hematoxylin and eosin (H&E) staining. ERK signaling pathway activation was detected through immunohistochemistry and Western blotting. The main morphological characteristics of injured muscle fibers around MTrPs include gathered circular or elliptical shapes of different sizes in the cross-section and continuous inflated and tapering fibers in the longitudinal section. After intramuscular injection of U0126 (ERK inhibitor), the mechanical pain threshold significantly increased. The reduction in mechanical hyperalgesia was accompanied by reduced ERK protein phosphorylation, myosin light chain kinase (MLCK) protein, p-MLC protein expression, and the cross-sectional area of skeletal muscle cells around MTrPs. An ERK inhibitor contributed to the attenuation of mechanical hyperalgesia in the rat myofascial pain model, and the increase in pain threshold may be related to MLCK downregulation and other related contraction-associated proteins by ERK.

Background and Objective: A novel option for myofascial pain (MFP) management and muscle regeneration is intramuscular collagen injections. The aim of the study was to evaluate the efficiency of intramuscular injections of collagen and lidocaine in decreasing MFP within masseter muscles., Methods: Myofascial pain within masseter muscles was diagnosed on the basis of the Diagnostic Criteria for Temporomandibular Disorders (II.1.A. 2 and 3). A total of 43 patients with diagnosed MFP within masseter muscles were enrolled to the study (17 male and 26 female, 40 ± 3.8 years old) and randomly divided into three groups. The first group received injections using 2 ml of collagen MD Muscle (Guna), the second group received 2 ml of 2% lidocaine without a vasoconstrictor, and the third group 2 ml of saline as a control (0.9% NaCl). All patients received repeated injections at one-week intervals (days 0 and 7). The visual analogue scale was used to determine pain intensity changes during each follow-up visit (days 0, 7, and 14) in each group. The masseter muscle activity was measured on each visit (days 0, 7, and 14) with surface electromyography (sEMG) (Neurobit Optima 4, Neurobit Systems)., Results: We found that sEMG masseter muscle activity was significantly decreased in Group I (59.2%), less in Group II (39.3%), and least in Group III (14%). Pain intensity reduction was 53.75% in Group I, 25% in Group II, and 20.1% in Group III., Conclusions: The study confirmed that intramuscular injection of collagen is a more efficient method for reducing myofascial pain within masseter muscles than intramuscular injection of lidocaine.

Introduction: Myofascial trigger points (MTrPs) are one of the most common and important causes of musculoskeletal pain. Ultrasound is a useful modality in examining musculoskeletal disorders. By applying compressive stress and observing changes in ultrasound images, the elastic modulus (Young's modulus) can be calculated. Our objective was to develop a novel method to distinguish MTrPs from normal tissues., Methods: A total of 29 subjects with MTrP in the sternocleidomastoid muscle were assessed. A force gauge was attached to a transducer to obtain stress levels. To obtain strain, images were recorded in both with stress and without stress states. By dividing the stress level by the measured strain, the elastic modulus was determined., Results: Elastic modulus in MTrPs and the normal part of the muscle were measured to be 13379.57 ± 1069.75Pa and 7078.24 ± 482.92Pa, respectively (P = 0.001). This indicated that MTrPs were stiffer than normal parts of the muscle., Conclusion: This study presents a new method for the quantitative measurement of the elastic modulus of MTrP, thereby distinguishing MTrPs from normal adjacent muscular tissue, with more simplicity and lower cost, compared to other ultrasound methods., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Purpose: To investigate the concurrent, face and content validity of an evaluation tool for Myofascial Adhesions in Patients after Breast Cancer (MAP-BC evaluation tool)., Methods: 1) Concurrent validity of the MAP-BC evaluation tool was investigated by exploring correlations (Spearman's rank Correlation Coefficient) between the subjective scores (0 -no adhesions to 3 -very strong adhesions) of the skin level using the MAP-BC evaluation tool and objective elasticity parameters (maximal skin extension and gross elasticity) generated by the Cutometer Dual MPA 580. Nine different examination points on and around the mastectomy scar were evaluated. 2) Face and content validity were explored by questioning therapists experienced with myofascial therapy in breast cancer patients about the comprehensibility and comprehensiveness of the MAP-BC evaluation tool., Results: 1) Only three meaningful correlations were found on the mastectomy scar. For the most lateral examination point on the mastectomy scar a moderate negative correlation (-0.44, p = 0.01) with the maximal skin extension and a moderate positive correlation with the resistance versus ability of returning or 'gross elasticity' (0.42, p = 0.02) were found. For the middle point on the mastectomy scar an almost moderate positive correlation with gross elasticity was found as well (0.38, p = 0.04) 2) Content and face validity have been found to be good. Eighty-nine percent of the respondent found the instructions understandable and 98% found the scoring system obvious. Thirty-seven percent of the therapists suggested to add the possibility to evaluate additional anatomical locations in case of reconstructive and/or bilateral surgery., Conclusions: The MAP-BC evaluation tool for myofascial adhesions in breast cancer patients has good face and content validity. Evidence for good concurrent validity of the skin level was found only on the mastectomy scar itself.

Objective-The objective of this study is to assess the discriminative ability of textural analyses to assist in the differentiation of the myofascial trigger point (MTrP) region from normal regions of skeletal muscle. Also, to measure the ability to reliably differentiate between three clinically relevant groups: healthy asymptomatic, latent MTrPs, and active MTrP. Methods-18 and 19 patients were identified with having active and latent MTrPs in the trapezius muscle, respectively. We included 24 healthy volunteers. Images were obtained by research personnel, who were blinded with respect to the clinical status of the study participant. Histograms provided first-order parameters associated with image grayscale. Haralick, Galloway, and histogram-related features were used in texture analysis. Blob analysis was conducted on the regions of interest (ROIs). Principal component analysis (PCA) was performed followed by multivariate analysis of variance (MANOVA) to determine the statistical significance of the features. Results-92 texture features were analyzed for factorability using Bartlett's test of sphericity, which was significant. The Kaiser-Meyer-Olkin measure of sampling adequacy was 0.94. PCA demonstrated rotated eigenvalues of the first eight components (each comprised of multiple texture features) explained 94.92% of the cumulative variance in the ultrasound image characteristics. The 24 features identified by PCA were included in the MANOVA as dependent variables, and the presence of a latent or active MTrP or healthy muscle were independent variables. Conclusion-Texture analysis techniques can discriminate between the three clinically relevant groups.

Objective: Myofascial pain syndrome (MPS) is a common disorder characterized by muscle pain if myofascial trigger points (MTrP) are stimulated. This study evaluated the effectiveness of far-infrared ray (FIR) patches in reducing the severity of pain in patients with MPS., Methods: A double-blind, randomized controlled study involving 125 patients with MPS and 201 MTrPs located in the trapezius muscle. A FIR patch was applied to 98 MTrPs for 24h in the intervention group (61 patients) and a placebo patch was applied to 91 MTrPs in the control group (57 patients) at the end. Pain intensity was measured using the visual analogue scale (V) while pressure pain threshold (P) and maximal pain tolerance (T) were measured using an algometer before and after treatment., Results: The mean age of the patients was 37.16 years old and 67% were female. There was a positive correlation between P and T (p<0.001). Older Age was associated with higher P and T due to poor skin sensitivity (p<0.001). V improved significantly in both groups to a similar extent, but only in the intervention group, P and T decreased significantly (which implied better skin sensitivity) (p<0.05). P and T decreased the most in the female group aged over 35, probably due to thinner skin in this subgroup., Conclusions: FIR and placebo patches were equally effective at relieving pain (with decreased V), but P and T dropped only in the intervention group with FIR patches. This probably resulted from FIR penetrated only to the skin layer and improved skin sensitivity with more blood circulation, but the muscle remained unaffected. Further studies should investigate the effect of longer exposure or higher energy applications., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background Neuroimaging studies revealed structural and functional changes in medication-overuse headache (MOH), but it remains unclear whether similar changes could be observed in other chronic pain disorders. Methods In this cross-sectional study, we investigated functional connectivity (FC) with resting-state functional magnetic resonance imaging (fMRI) and white matter integrity using diffusion tensor imaging (DTI) to measure fractional anisotropy (FA) and mean diffusivity (MD) in patients with MOH ( N = 12) relative to two control groups: patients with chronic myofascial pain (MYO; N = 11) and healthy controls (CN; N = 16). Results In a data-driven approach we found hypoconnectivity in the fronto-parietal attention network in both pain groups relative to CN (i.e. MOH < CN and MYO < CN). In contrast, hyperconnectivity in the saliency network (SN) was detected only in MOH, which correlated with FA in the insula. In a seed-based analysis we investigated FC between the periaqueductal grey (PAG) and all other brain regions. In addition to overlapping hyperconnectivity seen in patient groups (relative to CN), MOH had a distinct connectivity pattern with lower FC to parieto-occipital regions and higher FC to orbitofrontal regions compared to controls. FA and MD abnormalities were mostly observed in MOH, involving the insula. Conclusions Hyperconnectivity within the SN along with associated white matter changes therein suggest a particular role of this network in MOH. In addition, abnormal connectivity between the PAG and other pain modulatory (frontal) regions in MOH are consistent with dysfunctional central pain control.

Background: Myofascial trigger points (MTrPs) are a highly prevalent source of musculoskeletal pain. Prolonged ongoing nociceptive input from MTrPs may lead to maladaptive changes in the central nervous system. It remains, however, unknown whether pain from MTrPs is associated with brain atrophy. In addition, stress, which may contribute to the formation of MTrPs, is also known to affect brain structures. Here, we address whether structural brain changes occur in patients with chronic pain originating from MTrPs and whether such changes are related to pain or stress., Methods: Voxel-based morphometry was used to compare grey-matter (GM) volumes in 21 chronic pain patients, with MTrPs in the bilateral upper trapezius muscles, with 21 healthy controls. Hyperalgesia was assessed by pressure pain thresholds, and stress was assessed by cortisol levels and anxiety questionnaires., Results: Patients exhibited normal stress levels but lowered pain thresholds. GM atrophy was found in dorsal and ventral prefrontal regions in patients. The GM density of the right dorsolateral prefrontal cortex correlated with pain thresholds in patients, i.e. the more atrophy, the lower pain threshold. GM atrophy was also found in the anterior hippocampus, but the atrophy was neither related to pain nor stress., Conclusions: Patients with chronic myofascial pain exhibit GM atrophy in regions involved in top-down pain modulation and in processing of negative affect. The relationship between the dorsolateral prefrontal cortex and pain thresholds suggests the presence of pain disinhibition. No evidence was found for the involvement of stress. It remains unclear whether the observed atrophy contributes to the development of the chronic pain state or is caused by the ongoing nociceptive input., Significance: Chronic myofascial pain, caused by myofascial trigger points, is associated with localized brain atrophy in areas involved in pain processing and modulation, among others. These findings extend previous knowledge about peripheral and spinal changes to the supraspinal level., (© 2016 European Pain Federation - EFIC®.)

A afferent fibers have been reported to participate in the development of the central sensitization induced by inflammation and injuries. Current evidence suggests that myofascial trigger points (MTrPs) induce central sensitization in the related spinal dorsal horn, and clinical studies indicate that A fibers are associated with pain behavior. Because most of these clinical studies applied behavioral indexes, objective evidence is needed. Additionally, MTrP-related neurons in dorsal root ganglia and the spinal ventral horn have been reported to be smaller than normal, and these neurons were considered to be related to A fibers. To confirm the role of A fibers in MTrP-related central changes in the spinal dorsal horn, we studied central sensitization as well as the size of neurons associated with myofascial trigger spots (MTrSs, equivalent to MTrPs in humans) in the biceps femoris muscle of rats and provided some objective morphological evidence. Cholera toxin B subunit-conjugated horseradish peroxidase was applied to label the MTrS-related neurons, and tetrodotoxin was used to block A fibers specifically. The results showed that in the spinal dorsal horn associated with MTrS, the expression of glutamate receptor (mGluR1α/mGluR5/NMDAR1) increased, while the mean size of MTrS-related neurons was smaller than normal. After blocking A fibers, these changes reversed to some extent. Therefore, we concluded that A fibers participated in the development and maintenance of the central sensitization induced by MTrPs and were related to the mean size of neurons associated with MTrPs in the spinal dorsal horn.

Deep fascia has long been considered a source of pain, secondary to nerve pain receptors becoming enmeshed within the pathological changes to which fascia are subject. Densification and fibrosis are among such changes. They can modify the mechanical properties of deep fasciae and damage the function of underlying muscles or organs. Distinguishing between these two different changes in fascia, and understanding the connective tissue matrix within fascia, together with the mechanical forces involved, will make it possible to assign more specific treatment modalities to relieve chronic pain syndromes. This review provides an overall description of deep fasciae and the mechanical properties in order to identify the various alterations that can lead to pain. Diet, exercise, and overuse syndromes are able to modify the viscosity of loose connective tissue within fascia, causing densification, an alteration that is easily reversible. Trauma, surgery, diabetes, and aging alter the fibrous layers of fasciae, leading to fascial fibrosis.

Background: Myofascial trigger points (MTrPs) are hyperirritable spots located in taut bands of muscle fibres. Electrophysiological studies indicate that abnormal electrical activity is detectable near MTrPs. This phenomenon has been described as endplate noise and it has been purported to be associated MTrP pathophysiology. Thus, it is suggested that MTrPs will be overlap the innervation zone (IZ). The purpose of this work was to describe the location of MTrPs and the IZ in the right upper trapezius., Methods: We screened 71 individuals and eventually enrolled 24 subjects with neck pain and active MTrPs and 24 neck pain-free subjects with latent MTrPs. Surface electromyography (sEMG) signals were detected using an electrode matrix during isometric contraction of the upper trapezius. A physiotherapist subsequently examined the subject's trapezius to confirm the presence of MTrPs and establish their location. IZ locations were identified by visual analysis of sEMG signals. IZ and MTrPs locations were described using an anatomical coordinate system (ACS), with the skin area covered by the matrix divided into four quadrants., Results: No significant difference was observed between active and latent MTrPs locations (P = 0.6). Forty-five MTrPs were in the third quadrant of the ACS, and 3 were included in second quadrant. IZs were located approximately midway between the seventh cervical vertebrae and the acromial angle in a limited area in the second and third quadrants. The mean distance between MTrP and IZ was 10.4 ± 5.8 mm., Conclusions: According to the acquired results, we conclude that IZ and MTrPs are located in well-defined areas in upper trapezius muscle. Moreover, MTrPs in upper trapezius are proximally located to the IZ but not overlapped.

Knee malalignment and associated pathological abnormal forces transmitted through the knee is thought to provoke joint protective mechanism in reflex arthrogenous muscle inhibition (AMI) and the start of the idiopathic knee osteoarthritis process. The current prevailing hypothesis is AMI initiates quadriceps muscle weakness, cause aberrant loading of the knee joint and focal cartilage destruction. This paper investigates for evidence in the literature if this conceptual framework is consistent with the clinical evidence, and if there is an alternative explanation to AMI hypothesis for the pathogenesis of idiopathic knee osteoarthritis. One crucial question yet to be answered by the AMI hypothesis is; where are the initial aggravating factors of reflex AMI emanate from? AMI hypothesis relies on joint damage and changes in joint homeostasis to provoke a reflex arthrogenous response which can be found later in the development of knee OA. Myofascial trigger point (MTrP) hypothesis only relies on muscle tightness, pain and weakness to detect early pathological neuromuscular changes including knee instability and falls in the elderly. AMI is implicated in the knee OA pathological process but much later on when there are changes in joint homeostasis and joint cartilage damage have occurred. Falls in the elderly is a result of early pathological neuromuscular changes. The MTrP hypothesis is more sensitive and advanced in the early detection of neuromuscular impairment and pathological changes, allowing early intervention, prevention of falls in the elderly and idiopathic knee osteoarthritis., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Objectives: To explore myoelectrical activity and muscle morphology of myofascial trigger points (MTrPs) in an injury model of rats., Methods: A total of 24 male SD rats were randomly divided into a control group (group A) and model group (group B). A blunt striking injury and eccentric exercise were applied to the vastus medialis (VM) of rats in group B for 8 weeks. Later, the palpable taut band (TB), local twitch response, myoelectrical activities and morphology in the two groups were examined., Results: An average of 2.5 (30/12) palpable TBs were detected in the VM in group B compared with none in group A. The MTrPs had two types of abnormal potential. Their amplitudes were significantly higher than those in the control group (p<0.01) but their durations showed no significant differences. A series of reflex contractions appeared in groups A and B in response to external stimulation to the ear. Their amplitude and duration in group B were significantly lower than those in group A. A series of lower fibrillation potentials repeatedly occurred in model MTrPs in group B. The morphology of MTrPs showed abnormal muscle fibres with large round or ellipse shapes in cross-section and enlarged tapering shapes in longitudinal section., Conclusions: Active MTrPs can be provoked by repeated blunt injury. Active MTrPs are a group of muscle fibres with abnormal shapes and abnormal myoelectrical potentials. External stimulation provokes low-voltage responses in MTrPs, which is different from the response of normal muscle fibres.

The examination of 112 women suffering from chronic cystitis has detected frequent comorbidity of genital, gastrointestinal, locomotor and pelvic varicose diseases. Myofascial syndrome, hemodynamic disorders and venous congestion play a leading role in development of pain syndrome in women with comorbid diseases of the small pelvis organs. Clinicopsychological investigation of such women has revealed frequent vegetative and psychoemotional disorders with predominance of anxiodepressive conditions. Pain, dysuria and anxiodepressive disorders are among causes of imbalance of the autonomic nervous system which acvitaves regulatory systems and has an impact on quality of life. Women with chronic cystitis show significant deterioration of quality of life. Combined treatment including physical factors and therapeutic exercise reduced treatment duration, frequency of exacerbations, raised cost effectiveness.

The article describes and compares the characteristics of myofascial trigger points (MTrPs) of the myofascial pain syndrome and the tender points (TePs) of the fibromyalgia syndrome. Many statements are hypothetical, because not all aspects of the disorders have been clarified in solid studies. Signs and symptoms of MTrPs: (1) palpable nodule, often located close to the muscle belly, (2) often single, (3) allodynia and hyperalgesia at the MTrP, (4) referral of the MTrP pain, (5) normal pain sensitivity outside the MTrPs, (6) local twitch response, (7) local contracture in biopsy material, (8) peripheral mechanism probable. Signs and symptoms of TePs: (1) no palpable nodule, (2) location often close to the muscle attachments, (3) multiple by definition, (4) allodynia and hyperalgesia also outside the TePs, (5) enhanced pain under psychic stress, (6) unspecific histological changes in biopsy material, (7) central nervous mechanism probable. The multitude of differences speak against a common aetiology and pathophysiology.

Macrophagic myofascitis (MMF) is an unusual inflammatory myopathy characterized by muscle infiltration by macrophages and lymphocytes. Here, we describe a case of MMF which is associated with rheumatoid arthritis. A 53-year-old Japanese rheumatoid arthritis (RA) patient presented with focal tenderness of lower extremities. Magnetic resonance imaging showed evidence of myofascitis involving fascias of anterior tibialis muscle. Muscle biopsy showed a unique pathological pattern of MMF. MMF is known to be associated with vaccination containing aluminum. However, our case was not related to aluminum containing vaccinations and etiologies are unknown. The possible link needs to be discussed.

Introduction: Pudendal nerve entrapment syndrome is a poorly known condition and thus rarely included in our differential diagnoses. First described by Amarenco in 1987., Development: The symptomatology is varied and can be confused with other entities, in particular the pelvic floor myofascial syndrome., Conclusions: The main symptom is neuropathic pain in the perineal area. The diagnosis is based on the clinical history, physical examination and the confirming neurophysiologic tests.

Objective: To investigate the changes in surface and intramuscular electromyographic (EMG) activity at latent trigger points (TrPs) in the extensor carpi radialis brevis muscle after injection of either glutamate or isotonic saline into latent TrPs in the infraspinatus muscle., Method: Nociceptive muscle stimulation was obtained by a bolus injection of glutamate (0.2 mL, 0.5 M) into a latent TrP located in the right infraspinatus muscle in 12 healthy volunteers. A bolus of isotonic saline (0.9%, 0.2 mL) injection served as control. Injections were guided by intramuscular EMG showing resting spontaneous electrical activity at the latent myofascial TrP in the infraspinatus muscle. Intramuscular (at the TrP) and surface EMG activities of both infraspinatus and extensor carpi radialis brevis muscles were recorded before, during, and after injection for a period of 6 minutes to monitor changes produced in EMG activity., Results: Glutamate injection into latent TrPs induced higher pain intensity than isotonic saline injection (P<0.001). The analysis of variance showed a significant increase in root mean square score of intramuscular EMG activity at TrP in the extensor carpi radialis brevis after glutamate (mean+/-SD: 212.0+/-215.6 microV) but not isotonic saline (mean+/-SD: 74.2+/-72.2 microV) injections (P<0.001). No changes in surface EMG activity were found. No significant changes in root mean square of intramuscular and surface EMG activity in the infraspinatus muscle were found., Conclusions: Our results show that an increased nociceptive activity at latent TrPs in the infraspinatus muscle may increase motor activity and sensitivity of a TrP in distant muscles at a same segmental level.

Spatial changes in pressure pain hypersensitivity are present throughout the cephalic region (temporalis muscle) in both chronic tension-type headache (CTTH) and unilateral migraine. The aim of this study was to assess pressure pain sensitivity topographical maps on the trapezius muscle in 20 patients with CTTH and 20 with unilateral migraine in comparison with 20 healthy controls in a blind design. For this purpose, a pressure algometer was used to assess pressure pain thresholds (PPT) over 11 points of the trapezius muscle: four points in the upper part of the muscle, two over the levator scapulae muscle, two in the middle part, and the remaining three points in the lower part of the muscle. Pressure pain sensitivity maps of both sides (dominant/non-dominant; symptomatic/non-symptomatic) were depicted for patients and controls. CTTH patients showed generalized lower PPT levels compared with both migraine patients (P = 0.03) and controls (P < 0.001). The migraine group had also lower PPT than healthy controls (P < 0.001). The most sensitive location for the assessment of PPT was the neck portion of the upper trapezius muscle in both patient groups and healthy controls (P < 0.001). PPT was negatively related to some clinical pain features in both CTTH and unilateral migraine patients (all P < 0.05). Side-to-side differences were found in strictly unilateral migraine, but not in those subjects with bilateral pain, i.e. CTTH. These data support the influence of muscle hyperalgesia in both CTTH and unilateral migraine patients and point towards a general pressure pain hyperalgesia of neck-shoulder muscles in headache patients, particularly in CTTH.

The generalized hypersensitivity associated with fibromyalgia syndrome (FMS) may in part be driven by peripheral nociceptive sources. The aim of the study was to investigate whether local and referred pain from active myofascial trigger points (MTrPs) contributes to fibromyalgia pain. FMS patients and healthy controls (n=22 each, age- and gender-matched) were recruited. The surface area over the upper trapezius muscle on each side was divided into 13 sub-areas (points) of 1cm in diameter for each point. Pressure pain threshold (PPT) and the local and referred pain pattern induced by manual palpation at 13 points bilaterally in the upper trapezius were recorded. Results showed that PPT levels at all measured points were significantly lower in FMS than controls. Multiple active MTrPs (7.4+/-2.2) were identified bilaterally in the muscle in FMS patients, but no active MTrPs were found in controls. The mid-fiber region of the muscle had the lowest PPT level with the largest number of active MTrPs in FMS and with the largest number of latent MTrPs in controls. The local and referred pain pattern induced from active MTrPs bilaterally in the upper trapezius muscle were similar to the ongoing pain pattern in the neck and shoulder region in FMS. In conclusion, active MTrPs bilaterally in the upper trapezius muscle contribute to the neck and shoulder pain in FMS. Active MTrPs may serve as one of the sources of noxious input leading to the sensitization of spinal and supraspinal pain pathways in FMS.

Objective: The aim of the present study was to investigate the presence of active and latent muscle trigger points (TrPs) in the forearm musculature on both affected and unaffected sides in patients with lateral epicondylalgia (LE) and healthy controls., Methods: Twenty-five patients with LE and 20 healthy matched controls participated. Both groups were examined for the presence of TrPs in the extensor carpi radialis brevis, extensor carpi radialis longus, extensor digitorum communis, and brachioradialis muscles in a blinded fashion. TrPs were identified in both affected and unaffected sides within the patient group. In the control group, TrPs were explored around the dominant side. Pressure pain thresholds (PPTs) were assessed on both affected and unaffected arms., Results: In the patient group, the number of active muscle TrPs in the affected side was 3.1 [95% confidence interval (CI): 2.8-3.4], whereas in the unaffected arm, only latent TrPs were found (mean: 2.2; 95% CI: 1.8-2.6). Active TrPs were only located on the affected side (P<0.001). Within the control group, the number of latent TrPs in the dominant arm was 0.4 (95% CI: 0.0-0.7), which was significantly lower than the number of latent TrPs in the unaffected arm (P<0.001) in patients. Therefore, latent muscle TrPs in the forearm musculature were associated with the unaffected side in the patient group as compared with the dominant arm in healthy controls: extensor carpi radialis brevis [odds ratio (OR)=66 (95% CI: 9.9-48.8)], extensor carpi radialis longus [OR=16 (95% CI: 3.7-29.6)], brachioradialis [OR=2.6 (95% CI: 0.3-27.1)], and extensor digitorum communis [OR=0.5 (95% CI: 0.4-0.8)]. PPTs were lower around the affected side than around the unaffected arm in patients (mean+/-SD: 274.5+/-90.4 KPa vs. 465.4+/-140.7 KPa; P<0.001) in the patient group. Finally, PPT from the extensor digitorum muscle in those patients with active TrPs (mean+/-SD: 244+/-70.4 KPa) was significantly lower (P<0.001) than PPT levels of patients with no TrP in the same muscle (mean+/-SD: 370+/-83.4 KPa)., Conclusions: Latent TrPs are present in forearm muscles on the unaffected side in patients with LE where active TrPs contribute to the pain on the affected arm. The presence of latent TrPs on the unaffected side in unilateral LE may be related to central sensitization and be a mechanism explaining bilateral pain in some patients with unilateral pathologies.

Subjects with myofascial pain of muscles of the neck region may present with various clinical symptoms. The aim of this study was to explore the demographics features, clinical findings and functional status in a group of patients presenting with myofascial pain of the cervical muscles. 94 cervical myofascial pain syndrome patients were recruited from the out-patient clinic. Evaluated of patient short form health survey (SF-36), pain, depression, patient demographics and physical examinations. Outcome measures; SF-36 Health Survey, visual analog scale, Beck Depression Inventory, history, physical examination. A total of 82 patients with a diagnosis of cervical myofascial syndrome were included in the study. All patients were in the young age group 37.4+/-9, and 87.8% were females. 53.1% had trigger points in the trapezius muscle with high percentage of autonomic phenomena like skin reddening, lacrimation, tinnitus and vertigo. 58.5% of the series had suffered from former cervical trauma and 40.2% also had fibromyalgia syndrome and 18.5% had benign Joint hypermobility syndrome. Younger female patients presenting with autonomic phenomena and early onset cervical injury should be examined for cervical myofascial pain syndrome and also for fibromyalgia syndrome since this study demonstrated a high percentage of fibromyalgia syndrome in these patients.

Objective: To investigate whether cross-sectional area (CSA) of the suboccipital muscles was associated with active trigger points (TrPs) in chronic tension-type headache (CTTH)., Design: Magnetic resonance imaging (MRI) of the cervical spine was performed in 11 females with CTTH aged from 26 to 50 yrs old. CSA for both rectus capitis posterior minor (RCPmin) and rectus capitis posterior major (RCPmaj) muscles were measured from axial T1-weighted images, using axial MRI slices aligned parallel to the C2/3 intervertebral disc. A headache diary was kept for 4 wks to record the pain history. TrPs in the suboccipital muscle were identified by eliciting referred pain to palpation, and increased referred pain with muscle contraction. TrPs were considered active if the elicited referred pain reproduced the head pain pattern and features of the pattern seen during spontaneous headache attacks., Results: Active TrPs were found in six patients (55%), whereas the remaining five patients showed latent TrPs. CSA of the RCPmin was significantly smaller (F = 13.843; P = 0.002) in the patients with active TrPs (right side: 55.9 +/- 4.4 mm; left side: 61.1 +/-: 3.8 mm) than in patients with latent TrPs (right side: 96.9 +/- 14.4 mm; left side: 88.7 +/- 9.7 mm). No significant differences were found for CSA of the RCPmaj between the patients with either active or latent TrP (P > 0.5)., Conclusions: It seems that muscle atrophy in the RCPmin, but not in the RCPmaj, was associated with suboccipital active TrPs in CTTH, although studies with larger sample sizes are now required. It may be that nociceptive inputs in active TrPs could lead to muscle atrophy of the involved muscles. Muscle disuse or avoidance behavior can also be involved in atrophy.

The aim of the study was to investigate if an abnormal brain response to pain exists in patients with myofascial pain syndrome (MPS) when stimulated in a hypersensitive myofascial trigger point (MTP). Event-related functional magnetic resonance imaging was used to characterize the brain response to pain evoked from an MTP. Activation patterns from patients were compared with those evoked from an equivalent site in healthy controls with stimulus intensity matched and pain intensity matched stimuli. Compared to healthy controls at matched stimulus intensity, patients experienced significantly higher pain intensity (hyperalgesia). The corresponding brain response revealed significantly enhanced somatosensory (SI, SII, inferior parietal, mid-insula) and limbic (anterior insula) activity and suppressed right dorsal hippocampal activity in patients compared with controls. At matched pain intensity, enhanced activity was found in the same somatosensory areas but not in limbic areas. Our results show that the hyperalgesic state observed in MPS patients was associated with abnormal hyperactivity in regions processing stimulus intensity and negative affect. We speculate that suppressed hippocampal activity might reflect stress-related changes in relation to chronic pain as an effective physical and emotional stressor.

Background: Myofascial pain is defined as pain that originates from myofascial trigger points in skeletal muscle. It is prevalent in regional musculoskeletal pain syndromes, either alone or in combination with other pain generators. The myofascial pain syndrome is one of the largest groups of under-diagnosed and under-treated medical problems encountered in clinical practice. Trigger points are commonly seen in patients with myofascial pain that can be responsible for localized pain in the affected muscles as well as referred pain patterns. Correct needle placement in a myofascial trigger point is vital to prevent complications and improve efficacy of the trigger point injection to help reduce or relieve myofascial pain. In the obese patients, these injections may not reach the target tissue. In the cervicothoracic spine, a misguided or misplaced injection can result in a pneumothorax. Here, we review an electromyographically guided trigger point injection technique to avoid this potential pitfall., Methods: Using a disposable Teflon coated hypodermic injection needle attached to an electromyography (EMG) machine, a trigger point injection can be performed utilizing electromyographic guidance. This guidance by observing motor unit action potentials (MUAPs) on the EMG screen helps confirm the needle placement to be within the muscle tissue and not in an adipose tissue or any other non-musculature structure., Results: The technique is simple when performed by a pain management specialist who has electromyographic training., Conclusion: This technique helps confirm proper needle placement within the cervicothoracic musculature in an obese patient in whom the musculature is not readily palpated. This, thus, reduces the potential for a pneumothorax by an improperly placed injection.

The aim of this study was to compare the findings on magnetic resonance imaging (MRI) in temporomandibular disorders (TMD) pain patients with clinical diagnoses of myofascial pain or arthralgia/osteoarthritis in combination with myofascial pain according to the Research Diagnostic Criteria for TMD. The temporomandibular joints of 60 consecutive patients, 19 with myofascial pain and 41 patients with arthralgia/osteoarthritis in combination with myofascial pain were examined clinically and with MRI. Overall the most common MRI findings were different kinds of disc displacements and structural bone changes, which were found in both pain groups. However, disc displacements were found significantly (P=0.002) more often in the group arthralgia/osteoarthritis in combination with myofascial pain. One hundred and four joints were found to have no clinical diagnosis of disc displacements, but 64 of these joints had findings of disc displacements on MRI. Joint fluid was found in both pain groups. Patients having a combination of disc displacement and joint fluid were significantly (P=0.047) more common in the pain group arthralgia/osteoarthritis in combination with myofascial pain. In conclusion, the MRI findings of different kinds of disc displacement and structural bone changes were common in TMD patients. The clinical diagnoses for subdivision into myogenous only or combined arthrogenous and myogenous pain groups were not confirmed by MRI.

Objective: Some patients with trochlear disorders have been found to suffer from concurrent migraine. However, a trochlear examination is not systematically done in patients with migraine. Moreover, a search for myofascial trigger points in the superior oblique muscle has never been reported in these patients., Methods: The trochlear region was examined in 20 participants with strictly unilateral migraine without side-shift and in 20 controls. Referred pain elicited by different maneuvers during manual palpation (ie, maintained pressure, active muscle contraction, and stretching of the superior oblique muscle) was assessed with a visual analog scale. All participants were headache free on the day of evaluation., Results: Sixteen participants with migraine (80%) perceived referred pain on examination of the trochlear area. It was described as a tightening sensation in the retro-orbital region, sometimes extending to the supraorbital region and the homolateral forehead. In 15 participants with migraine, both the active contraction and the stretching of the muscle increased the referred pain, which was consistent with definite myofascial trigger points. All the definite trigger points were ipsilateral to the side of the headache. Conversely, only 5 controls (20%) had referred pain. None of them had definite myofascial trigger points because muscle stretching did not increase the intensity of pain. The intensity of referred pain at each stage of the trochlear examination was greater in subjects with migraine than in controls (P<0.001)., Conclusion: Patients with unilateral migraine commonly perceive referred pain from the trochlear area that probably comes from the myofascial trigger points. Myofascial disorders in the trochlear region might contribute to the perpetuation of concomitant migraine.

Chronic pelvic pain is a potentially devastating condition that affects many women with severe consequences. A multifaceted condition, chronic pelvic pain enjoys a diverse etiology, a myriad of treatments, and a correspondingly irregular response to therapy. The condition can be associated with severe physical dysfunction in relation to voiding, defecation, and sexual function. Although emphasis has been placed on surgical approaches to therapy, there is increasing interest in alternative therapies, particularly using the principles of the treatment of myofascial dysfunction.

Myofascial pain syndrome is a painful musculoskeletal condition, and a quite common cause of chronic pain. It is characterized by the development of trigger points that are locally tender when active, and refer pain through specific patterns to other areas of the body. Its etiological factors are various; trauma, vertebral column diseases, systemic disorders, psychological distress, lack of motion, and chilling of the body parts. Myofascial pain syndrome may be misdiagnosed as arising from a visceral source especially if its probability is not kept in mind and a proper patient examination is lacking. Although there are many therapeutic approaches, trigger point injections can be diagnostic and therapeutic.

Spontaneous electrical activity, interpreted as motor endplate activity, has been reported at muscle trigger points. This study examined whether the motor endplate region, identified by electromyography, is more sensitive to noxious stimuli than other muscle sites. We induced pain in the brachial biceps muscles of 21 healthy subjects by injecting capsaicin (30 microg/0.1 ml) and NaCl (5%/0.2 ml) in the motor endplate region and at electrically silent muscle sites. Needle and evoked pain were measured by a visual analogue scale (VAS) (0-10) and the short form of the McGill Pain Questionnaire. The needle pain in the motor endplate region differed both in intensity and quality from that at other sites. The maximal pain after NaCl 5% was higher, and the VAS area-under-the-curve for NaCl 5% and capsaicin were larger, in the motor endplate region than in other sites. A higher density of muscle nociceptors in the vicinity of the motor endplate region may account for the observed differences in pain. These findings may have clinical implications for the treatment of musculoskeletal pain conditions.

In skeletal muscle, a local increase of acetylcholine (ACh) in a few end plates has been hypothesized to cause the formation of contraction knots that can be found in myofascial trigger points. To test this hypothesis in rats, small amounts of an acetylcholinesterase inhibitor [diisopropylfluorophosphate (DFP)] were injected into the proximal half of the gastrocnemius muscle, and the muscle nerve was electrically stimulated for 30-60 min for induction of muscle twitches. The distal half of the muscle, which performed the same contractions, served as a control to assess the effects of the twitches without DFP. Sections of the muscle were evaluated for morphological changes in relation to the location of blocked end plates. Compared with the distal half of the muscle, the DFP-injected proximal half exhibited significantly higher numbers of abnormally contracted fibers (local contractures), torn fibers, and longitudinal stripes. DFP-injected animals in which the muscle nerve was not stimulated and that were allowed to survive for 24 h exhibited the same lesions but in smaller numbers. The data indicate that an increased concentration of ACh in a few end plates causes damage to muscle fibers. The results support the assumption that a dysfunctional end plate exhibiting increased release of ACh may be the starting point for regional abnormal contractions, which are thought to be essential for the formation of myofascial trigger points.

Objective: Substance P (SP), a neurotransmitter stored within the afferent nociceptive fibers, is likely to be involved in the pathogenesis of musculoskeletal pain. We investigated SP immunoreactive (SP-ir) nerve fibers in the upper trapezius of patients with fibromyalgia (FM) and myofascial pain syndrome (MPS) by immunochemistry., Methods: Trapezius muscle obtained from tender points of 9 women with primary FM, from trigger points of 9 women with regional myofascial pain, and from 9 control women were immunostained with anti-SP sera. Quantitative evaluation was performed by computerized image analysis., Results: No significant differences in the number of SP-ir areas were detected between groups (one way ANOVA: p = 0.2); in contrast, mean optical density (OD) of SP-ir showed a significant difference comparing the groups (one way ANOVA: p < 0.0001). Mean OD of the immunostaining for SP was statistically greater in trapezius muscle of patients with MPS (0.594 +/- 0.096) compared to specimens from patients with FM (0.436 +/- 0.140) (p < 0.05) and controls (0.314 +/- 0.105) (p < 0.05); mean OD of immunostaining for SP was greater in FM specimens than in controls (p < 0.05)., Conclusion: Our results point to a peripheral hyperactivity of the peptidergic nervous system in FM as well as in MPS. These findings support the notion of pathogenetic involvement of the afferent nervous system in the development and perception of myofascial pain.

The subnucleus interpolaris (Vi) has been identified as a major recipient for trigeminal ganglionic input from jaw muscles, and contains neurons with nociceptive properties similar to those in the subnucleus caudalis (Vc). Therefore, Vi may be another important site for processing craniofacial muscle nociception. The aims of present study were to define functional properties of Vi neurons that receive input from masseter muscle afferents by characterizing their responses to electrical, mechanical, and to chemical stimulation of the muscle. Ninety cells were identified as masseter muscle units in 11 adult cats. Most of these units (79%) received additional inputs from orofacial skin. Following the intramuscular injection of 5% hypertonic saline, 49% of the cells showed a significant modulation of either the resting discharge and/or responses to innocuous mechanical stimulation on their cutaneous receptive fields (RFs). The most common response to saline injection was an induction or facilitation of resting discharge which declined as an exponential decay function, returning to pre-injection level within 3-4 min. Forty-five percent of the muscle units that were tested with mechanical stimulation (13/29) showed a prolonged inhibition of mechanically-evoked responses. In most cases (8/13), the inhibitory response was accompanied by initial facilitation. The observations that Vi contained a population of neurons that receive small diameter muscle afferent inputs, responded to noxious mechanical stimulation on the muscle and to a chemical irritant that is known to produce pain in humans provide compelling evidence for the involvement of Vi in craniofacial muscle pain mechanisms.

Background and Objectives: Myofascial pain syndrome (MPS) is a common condition often resulting in referral to a pain clinic. The epidemiology, pathogenesis, and various diagnostic tools are reviewed, and a variety of treatment methods are discussed., Methods: Extensive periodical literature and textbooks are reviewed, and selected manuscripts are critically analyzed., Results: The incidence of MPS with associated trigger points appears to vary between 30 and 85% of people presenting to pain clinics, and the condition is more prevalent in women than in men. Patients complain of regional persistent pain, ranging in intensity and most frequently found in the head, neck, shoulders, extremities, and low back. Muscle histologic abnormalities have been described in some studies. Similarly, electromyographic, thermographic, and pressure algometric studies have inconsistently identified abnormalities. A multidisciplinary approach to treatment appears to be most beneficial and may include such modalities as trigger-point injections, dry needling, stretch and spray, and transcutaneous electrical nerve stimulation., Conclusions: The definitive pathogenesis of MPS is currently unknown, and no single diagnostic method is consistently positive. While trigger-point injection is the most widely employed method of treatment, other modes of therapy have also proved to be effective.

While manual palpation is the most important method for evaluation of tender myofascial tissues, it lacks reliability. Therefore, we have developed an instrument, called a 'palpometer', which allows the measurement of pressure exerted during palpation. The palpometer consists of a thin pressure-sensitive plastic device attached to the palpating finger, and of a scale recording the pressure applied to the device. Known forces were applied to the pressure sensitive device under various experimental conditions and the corresponding values were read on the palpometer scale. Then 14 observers, blinded to the palpometer scale, palpated the temporal muscle on the same subject twice, with an interval of 1 week. A highly significant correlation was found between palpometer recordings and forces applied to the pressure-sensitive device (P < 0.0001). Exerted force at a given palpometer value varied 3.1% within and 7.2% between 2 observers. During palpation of the temporal muscle pressure intensities within the 14 observers did not differ significantly from week to week (P = 0.68). Between the 14 observers pressure intensities varied considerably with a range of 73.5-196 arbitrary units. Thus, a reliable instrument for measuring pressure intensities during palpation of myofascial tissue has been developed. The large variation in palpation pressures between observers indicates that palpation of tender myofascial tissue may be considerably improved by use of the palpometer. This instrument will be indispensable in research studies employing palpation and in the training of physicians to diagnose myofascial pain disorders.

Four experts on myofascial pain syndrome (MFP) performed trigger point examinations and 4 experts on fibromyalgia performed tender point examinations on 3 groups of subjects (7 patients with fibromyalgia, 8 with MFP, and 8 healthy persons) while blinded as to diagnosis. Local tenderness was common in both disease groups (65-82%), but was elicited in a greater proportion of MFP experts' examinations (82%). Active trigger points were found in about 18% of examinations of patients with fibromyalgia and MFP, but latent trigger points were rare in all groups. A more liberal definition of trigger point, however, resulted in a 38 and 23% positive rate among patients with fibromyalgia and MFP, respectively. Taut muscle bands and muscle twitches were common (50 and 30%, respectively) and noted equally in all 3 diagnostic groups. Problems with reliability were identified for taut bands, muscle twitch, and active trigger points. Our data are exploratory and tentative, but suggest that attention to definition and reliability are required to advance our knowledge of these common syndromes.

In a controlled, cross-over study the effect of low level laser therapy (LLLT) was evaluated. During a five weeks period forty-seven female laboratory technicians received six laser and six placebo treatments to tender points in the neck and shoulder girdle. Subjects rated the placebo treatment significantly more beneficial than LLLT (p = .04). There was no reduction in consumption of analgesics associated with either laser or placebo treatment. The results indicate no beneficial effect of LLLT for myofascial pain.

The carrying ability of a spinal disc disturbed under axis load is found to be due to the displacement of a vertebra lying above it. The constant stretching of the extensively innervated soft tissues of the spine brings about a steady irritation process within the limits of the segmental part of the spinal cord and dysfunction of short profound muscles of the back.

Seven foci of pain (trigger points) were identified in the triceps brachii, infraspinatus, adductor-pectineus, peroneus longus, gluteus medius, ileocostorum lumborum, and quadriceps femoris muscles in 48 lame dogs. The dogs had been lame for 1 day to 150 weeks (mean, 24 weeks). Thirty-one dogs had been treated unsuccessfully with corticosteroids, nonsteroidal anti-inflammatory drugs, analgesics, or acupuncture. Palpating the trigger points induced severe pain. Treatment consisted of weekly stimulation of the trigger points by needling or injection of a local anesthetic. The mean treatment period was 2.8 weeks. Excellent results and complete recovery were observed in 34 dogs (60%).

There continues to be an emerging body of literature related to fibromyalgia and the related conditions chronic fatigue syndrome and myofascial pain. During the past year, the most notable contributions included a large multicenter study providing new diagnostic criteria for the classification of fibromyalgia and clinical studies describing the overlap of fibromyalgia, chronic fatigue syndrome, and myofascial pain. Pathophysiologic studies were often preliminary and uncontrolled but the focus of these studies on abnormal nociception, neurohormones, and muscle metabolism provides an exciting hypothesis to unify pain, fatigue, and sleep disturbances, the primary symptoms of fibromyalgia. Unfortunately, new therapeutic trials were neither innovative nor especially encouraging.

In 119 patients referred with suspected fibromyalgia, biopsies from the quadriceps muscle were analyzed for "rubber band" morphology, and isokinetic quadriceps strength was measured. Eighty-four fulfilled the criteria for fibromyalgia, 26 had chronic myofascial pain (CMP) and 9 had other diseases including 5 with concomitant fibromyalgia. Twenty-four CMP patients and 48 fibromyalgia patients were randomly selected to match with regard to sex, age, smoking and drinking habits. "Rubber band" morphology was blindly graded on a biopsy score scale from 0 to 2. A statistically significant difference in biopsy score was found between the two matched groups (P = 0.003); median biopsy score in fibromyalgia was 0.42 and 0.25 in CMP. A cut-off value at 0.33 gave a specificity of 71% and a sensitivity of 63%. Isokinetic muscle strength did not differ in the fibromyalgia and CMP groups and was not related to the biopsy score. "Rubber band" morphology is seen more often in fibromyalgia patients than in CMP patients. The exact genesis of this phenomenon is still unknown but theories connected with the possible pathogenesis of the syndrome are presented.

Primary fibromyalgia syndrome (PFS) is a common form of nonarticular rheumatism with diffuse musculoskeletal aching and stiffness at multiple sites and tender points at characteristic locations. Nonmusculoskeletal "systemic" symptoms, eg, fatigue, poor sleep, irritable bowel symptoms, and chronic headaches, are also common. Although PFS is similar to myofascial pain syndrome (MPS) in that both conditions cause muscle pain and tenderness, important differences exist. Unlike PFS, muscle pain in MPS is usually local or regional, accompanied by trigger points. Unlike tender points, trigger points produce a referral pain pattern specific to each muscle. Moreover, "systemic" features of PFS are usually absent in MPS. Common and important pathologic changes in muscle in PFS are moth-eaten appearance of Type I fiber by histochemistry, and myofibrillar lysis with glycogen and mitochondria deposition by electron microscopy; inflammatory changes are absent by light microscopy. Recent investigations have shown that PFS is a characteristic clinical entity. Further controlled studies are, however, essential to establish the pathologic changes in tender muscles in PFS.

Trigger points (TPs) in muscles of the lower torso associated with the spine are an important cause of low back pain. The quadratus lumborum is the muscle most commonly involved, but TPs located there are often overlooked because of inadequate physical examination techniques. TPs in the lower rectus abdominis refer pain horizontally across the low back, and those in the iliopsoas refer pain in a vertical pattern, parallel to the lumbosacral spine. The pain pattern of TPs in the serratus posterior inferior is noted in the region of the muscle itself.