Endplate potentials are common to midfiber myofacial trigger points

OBJECTIVES: To compare the prevalence of motor endplate potentials (noise and spikes) in active central myofascial trigger points, endplate zones, and taut bands of skeletal muscle to assess the specificity of endplate potentials to myofascial trigger points. DESIGN: This nonrandomized, unblinded needle examination of myofascial trigger points compares the prevalence of three forms of endplate potentials at one test site and two control sites in 11 muscles of 10 subjects. The endplate zone was independently determined electrically. Active central myofascial trigger points were identified by spot tenderness in a palpable taut band of muscle, a local twitch response to snapping palpation, and the subject's recognition of pain elicited by pressure on the tender spot. RESULTS: Endplate noise without spikes occurred in all 11 muscles at trigger-point sites, in four muscles at endplate zone sites outside of trigger points (P = 0.024), and did not occur in taut band sites outside of an endplate zone (P = 0.000034). CONCLUSIONS: Endplate noise was significantly more prevalent in myofascial trigger points than in sites that were outside of a trigger point but still within the endplate zone. Endplate noise seems to be characteristic of, but is not restricted to, the region of a myofascial trigger point.     

Randomized controlled study of the antinociceptive effect of ultrasound on trigger point sensitivity: novel applications in myofascial therapy?

OBJECTIVE : To investigate whether therapeutic ultrasound modulates the pain sensitivity of myofascial trigger points. DESIGN: Repeated measures, single-blinded randomized controlled trial of ultrasound treatment of trigger points. SETTING: Outpatient injury rehabilitation clinic. SUBJECTS: Forty-four patients (22 males, 22 females) with trigger points identified within the trapezius muscle. INTERVENTIONS: Five-minute therapeutic intensity of ultrasound versus 5-min low-intensity application of ultrasound to a trapezius myofascial trigger point locus. MAIN MEASURES: Pain pressure threshold readings were measured at the trapezius trigger point site before and after exposure to the ultrasound intervention. RESULTS: Pain pressure threshold scores increased an average of 44.4 (14.2)% after therapeutic exposure to ultrasound (pre-ultrasound test 35.4 (8.5) N, post-ultrasound test 51.1 (12.8) N). No significant difference in pain pressure threshold scores was observed with low-intensity ultrasound exposures (pre-ultrasound 36.1 (6.1) N, post-ultrasound 36.6 (4.8) N). CONCLUSIONS: Therapeutic exposures to ultrasound reduce short-term trigger point sensitivity. Ultrasound may be a useful clinical tool for the treatment and management of trigger points and myofascial pain syndromes.     

Myofascial trigger points

Painful conditions of the musculoskeletal system, including myofascial pain syndrome, constitute some of the most important chronic problems encountered in a clinical practice. A myofascial trigger points is a hyperirritable spot, usually within a taut band of skeletal muscle, which is painful on compression and can give rise to characteristic referred pain, motor dysfunction, and autonomic phenomena. Trigger points may be relieved through noninvasive measures, such as spray and stretch, transcutaneous electrical stimulation, physical therapy, and massage. Invasive treatments for myofascial trigger points include injections with local anesthetics, corticosteroids, or botulism toxin or dry needling. The etiology, pathophysiology, and treatment of myofascial trigger points are addressed in this article.     

Myofacial trigger point

Myofascial trigger points are one of the most common causes of acute and chronic musculoskeletal pain. Contrary to popular belief, myofascial trigger points can be primary, and not just secondary due to other non-muscular pathology. The main criteria, for which the interrater reliability has been established, include the presence of a taut band, a local twitch response, an exquisite tender point within the taut band, and typical referred pain patterns. During the past few years, the actual existence and high prevalence of myofascial trigger points are supported by worldwide research findings. The “energy crisis theory” describes the peripheral pathophysiologic events of myofascial trigger points. In most cases myofascial trigger points can be treated successfully both in acute and chronic pain syndromes. Several treatment options are available including manual therapy, injections, dry needling, and electrotherapeutic modalities. In some cases neuroplastic changes in the spinal dorsal horn and sympathetic-afferent coupling play a role in the development of chronic pain syndromes and complicate the treatment.      

Myofasziale Triggerpunkte

Myofascial trigger points are one of the most common causes of pain in the musculoskeletal system. They are characterized by a palpable nodule-like thickening in skeletal muscle within a taut band and a pain projection area. The etiology of myofascial trigger points is not fully understood but they are probably based on an interaction of increased local muscle tension close to neuromuscular junctions and an inflammatory component. Postural abnormalities and abnormal movement patterns also play a role. For the treatment of trigger points many techniques are available but systematic studies to prioritize or sequence the different treatment approaches are lacking. Following pragmatic considerations preference should first be given to non-invasive techniques, such as local postisometric relaxation, followed by dry needling and ultrasound. If the neurogenic inflammation component predominates the use of a local anesthetic or botulinum toxin can be considered. Each trigger point therapy should be integrated in manual-medical concepts including consideration of possible chain reactions.     

Symptomatology and clinical pathophysiology of myofascial pain

Myofascial pain syndromes, fibromyalgia, and articular dysfunctions may all be contributing to our patients' ubiquitous musculoskeletal pain problems that generally are poorly understood and poorly managed. Thepectoralis minor myofascial pain syndrome, for example, results from trigger points (TrPs) activated by stress overload of the muscle. Symptoms of pain referred to the shoulder and ulnar aspect of the arm and forearm, and of pain on reaching around and behind the body, are characteristic. Findings include restricted stretch range of motion and some weakness of the muscle, taut bands of muscle fibers, and focal trigger point tenderness of each taut band on palpation. Snapping palpation at the TrP elicits a local twitch response (LTR). The increased muscle tension of a pectoralis minor syndrome commonly entraps the lower trunk of the brachial plexus, producing symptoms of a cervical radiculopathy.     

Stimulation of myofascial trigger points with ultrasound induces segmental antinociceptive effects: a randomized controlled study

Musculoskeletal pain affects a significant proportion of the general population. The myofascial trigger point is recognized as a key factor in the pathophysiology of musculoskeletal pain. Ultrasound is commonly employed in the treatment and management of soft tissue pain and, in this study, we set out to investigate the segmental antinociceptive effect of ultrasound. Subjects (n=50) with identifiable myofascial trigger points in the supraspinatus, infraspinatus and gluteus medius muscles were selected from an outpatient rehabilitation clinic and randomly assigned to test or control groups. Test subjects received a therapeutic dose of ultrasound to the right supraspinatus trigger point while control groups received a sham (null) exposure. Baseline pain pressure threshold (PPT) readings were recorded at the ipsilateral infraspinatus and gluteus medius trigger-point sites prior to ultrasound exposure. The infraspinatus point was chosen due to its segmental neurologic link with the supraspinatus point; the gluteus medius acted as a segmental control point. Following the ultrasound intervention, PPT readings were recorded at 1, 3, 5, 10 and 15 min intervals at both infraspinatus and gluteus medius trigger points; the difference between infraspinatus and gluteus medius PPT values, PPT seg, represents the segmental influence on the PPT. The ultrasound test group demonstrated statistically significant increases in PPT seg (decreased infraspinatus sensitivity) at 1, 3 and 5 min, when compared with PPT seg in the sham ultrasound group. These results establish that low-dose ultrasound evokes short-term segmental antinociceptive effects on trigger points which may have applications in the management of musculoskeletal pain.     

Analysis of chronic myofascial pain in the upper trapezius muscle of breast cancer survivors and women with neck pain

Myofascial trigger points are present in dysfunctioning muscles and are associated with several diseases. However, the scientific literature has not established whether myofascial trigger points of differing etiologies have the same clinical characteristics. Thus, the objective of the present study was to compare the intensity of myofascial pain, catastrophizing, and the pressure pain threshold at myofascial trigger points among breast cancer survivors and women with neck pain. This was a cross-sectional study that included women over 18 years old complaining of myofascial pain in the upper trapezius muscle region for more than 90 days, equally divided into breast cancer survivors (n = 30) and those with neck pain (n = 30). For inclusion, the presence of a bilateral, active, and centrally located trigger point with mean distance from C7 to acromion in the upper trapezius was mandatory. The measures of assessment were: pain intensity, catastrophizing, and the pressure pain threshold at the myofascial trigger points. A significant difference was observed only when comparing pain intensity (p < 0.001) between the breast cancer survivors (median score: 8.00 points, first quartile: 7.00 points, third quartile: 8.75 points) and women with neck pain (median score: 2.50 points, first quartile: 2.00 points, third quartile: 4.00 points). No significant difference was found between groups in catastrophizing and pressure pain threshold. The conclusion of this study was that breast cancer survivors have a higher intensity of myofascial pain in the upper trapezius muscle when compared to patients with neck pain, which indicates the need for evaluation and a specific intervention for the myofascial dysfunction of these women.     

Effect of Treatment on Trigger Points

Patients with muscle pain complaints commonly are seen by clinicians treating pain, especially pain of musculoskeletal origin. Myofascial trigger points merit special attention because its diagnosis requires examinations skills and its treatment requires specific techniques. If undiagnosed, the patients tend to be overinvestigated and undertreated, leading to chronic pain syndrome. Patients with myofascial pain syndrome present primarily with painful muscle(s) and restricted range of motion of the relevant joint. Palpable painful taut bands are named trigger points and are the main and pathognomonic finding on physical examination. Eliciting local twitch response and referred pain requires experience and examination skills. It may be useful to classify the patient as having acute or chronic, and as having primary or secondary, myofascial pain so the decision on the details of treatment can be curtailed to the needs of each patient. Effective treatment modalities are local heat and cold, stretching exercises, spray-and-stretch, needling, local injection, and high-power pain threshold ultrasound.     

Treatment of myofascial pain

OBJECTIVE: To investigate the effectiveness of ultrasound treatment and trigger point injections in combination with neck-stretching exercises on myofascial trigger points of the upper trapezius muscle. DESIGN: Depression and anxiety associated with chronic pain were assessed using the Beck Depression Inventory (BDI) and the Taylor Manifest Anxiety Scale (TMAS). The study population comprised 102 patients who had myofascial trigger points in one side of the upper trapezius. The patients were randomly assigned to one of three groups: group 1 received ultrasound therapy to trigger points in conjunction with neck-stretching exercises; group 2 received trigger point injections and performed neck-stretching exercises; and group 3, the control group, performed neck-stretching exercises only. Treatment effectiveness was assessed using subjective pain intensity (PI) with a visual analog scale, pressure pain threshold (PT) with algometry, and range of motion (with a goniometer) of the upper trapezius muscle. RESULTS: Compared with the control group, patients in groups 1 and 2 had a statistically significant reduction in PI, an increase in PT, and an increase in range of motion. There were no statistically significant differences between treatment groups 1 and 2. Although not statistically significant, patients in the control group had better results at the 3-mo follow-up. The BDI scores indicated depression in 22.9% of the patient, with 4.8% of the patients having severe depression. High anxiety scores on the TMAS were present in 89.3% of the patients. When BDI and TMAS scores were compared with PI or PT levels, no significant correlations were found, but when compared with pain duration before treatment, correlations were significant. CONCLUSIONS: Patients with myofascial pain syndrome had higher scores for anxiety than for depression. When combined with neck stretching exercises, ultrasound treatment and trigger point injections were found to be equally effective.     

Trigger points and myofascial pain: toward understanding how they affect headaches

Myofascial pain, referred from hyperalgesic trigger points located in skeletal muscle and its associated fascia, is a common cause of persistent regional pain. Clinical and experimental literature on manifestations, pathophysiology, and management of pain from myofascial trigger points is reviewed with priority given to how pain referred from trigger points generates, triggers, and maintains headaches—especially chronic and recurrent ones. Because treating myofascial problems may be the only way to offer complete relief from certain types of headache, clinicians must learn to diagnose and manage trigger points in neck, shoulder, and head muscles.     

Myofascial Trigger Points: An Evidence-Informed Review

Abstract

This article provides a best evidence-informed review of the current scientific understanding of myofascial trigger points with regard to their etiology, pathophysiology, and clinical implications. Evidence-informed manual therapy integrates the best available scientific evidence with individual clinicians' judgments, expertise, and clinical decision-making. After abrief historical review, the clinical aspects of myofascial trigger points, the interrater reliability for identifying myofascial trigger points, and several characteristic features are discussed, including the taut band, local twitch response, and referred pain patterns. The etiology of myofascial trigger points is discussed with a detailed and comprehensive review of the most common mechanisms, including low-level muscle contractions, uneven intramuscular pressure distribution, direct trauma, unaccustomed eccentric contractions, eccentric contractions in unconditioned muscle, and maximal or sub-maximal concentric contractions. Many current scientific studies are included and provide support for considering myofascial trigger points in the clinical decision-making process. The article concludes with a summary of frequently encountered precipitating and perpetuating mechanical, nutritional, metabolic, and psychological factors relevant for physical therapy practice. Current scientific evidence strongly supports that awareness and working knowledge of muscle dysfunction and in particular myofascial trigger points should be incorporated into manual physical therapy practice consistent with the guidelines for clinical practice developed by the International Federation of Orthopaedic Manipulative Therapists. While there are still many unanswered questions in explaining the etiology of myofascial trigger points, this article provides manual therapists with an up-to-date evidence-informed review of the current scientific knowledge.     

Bilateral activation of motor unit potentials with unilateral needle stimulation of active myofascial trigger points

OBJECTIVE: The objective of this study was to determine if there are electromyographic differences between active and latent myofascial trigger points (MTrPs) during trigger point needling. DESIGN: A total of 21 subjects were recruited prospectively. The experimental group consisted of 13 subjects who had active myofascial pain in the neck for >6 mos. The age-matched, control group consisted of eight subjects without neck pain but with taut bands in the cervical musculature. The active MTrPs (or latent MTrPs in the control group) were identified in the trapezius or levator scapulae muscles, then needle electrodes were inserted ipsilaterally into the muscle with the MTrPs and into the same muscle on the contralateral side. Electromyographic activity was recorded bilaterally with a dual-channel electromyographic machine, and local twitch responses were obtainedusinganacupuncturedryneedlingtechniqueonlyonthesideoftheactiveMTrPs. RESULTS: We demonstrated that in subjects with active MTrPs, bilateral motor unit activation could be obtained with unilateral needle stimulation of the trigger point. In contrast, in all the subjects with latent MTrPs, only unilateral motor unit activation could be obtained in the muscle on the same side of the needle stimulation. The motor unit potentials seen on the electromyograph were similar in morphology to a fasciculation potential but more complex. CONCLUSION: We demonstrated bilateral or mirror-image electromyographic activity associated with unilateral needle stimulation of active MTrPs. We have found no previous mention of this phenomenon in the literature. Our study supports the concept that the perpetuation of pain and muscle dysfunction in active MTrPs may be related to abnormal central nervous system processing of sensory input at the level of the spinal cord.     

Change the Myofascial Pain and Range of Motion of the Temporomandibular Joint Following Kinesio Taping of Latent Myofascial Trigger Points in the Sternocleidomastoid Muscle

[Purpose] The purpose of this study was to identify the changes in the myofascial pain and range of the motion of temporomandibular joint when Kinesio taping is applied to patients with latent myofascial trigger points of the sternocleidomastoid muscle. [Subjects and Methods] The subjects were 42 males and females aged 20 to 30 years (male 17, female 25). They were randomly divided into the control group and the experimental group, which would receive Kinesio taping. Kinesio taping was applied to the sternocleidomastoid muscle three times per week for two weeks. The pain triggered when the taut band or nodule was palpated was measured. Pain intensity was measured using the visual analog scale (VAS) and pressure pain threshold (PPT). The range of motion of the temporomandibular joint was measured. In all subjects, VAS, PPT, and range of motion of the temporomandibular joint were measured before and after the intervention. [Results] In the experimental group, it was found that pain in the SCM was relived, as the VAS and PPT score decrease significantly and range of motion of temporomandibular joint increase significantly. In comparison between the groups, significant differences were shown in the VAS and PPT scores and in the range of motion of the temporomandibular joint. [Conclusion] Kinesio taping is thought to be an intervention method that can be applied to latent myofascial trigger points.Key words: Kinesio taping, Latent myofascial trigger point, Sternocleidomastoid muscle     

New views of myofascial trigger points: etiology and diagnosis

Simons DG. New views of myofascial trigger points: etiology and diagnosis.Two studies appearing in Archives, one by Shah and colleagues and another one by Chen and colleagues, present groundbreaking findings that can reduce some of the controversy surrounding myofascial trigger points (MTPs). Both author groups recognize the ubiquity of this disease and the importance to patients of health care professionals becoming better acquainted with the cause and identification of MTPs. The integrated hypothesis is the most credible and most complete proposed etiology of MTPs. However, the feedback loop suggested in this hypothesis has a few weak links, and studies by Shah and colleagues in particular supply a solid link for one of them. The feedback loop connects the hypothesized energy crisis with the milieu changes responsible for noxious stimulation of local nociceptors that causes the local and referred pain of MTPs. Shah’s reports quantify the presence of not just 1 noxious stimulant but 11 of them with outstanding concentrations of immune system histochemicals. The results also strongly place a solid histochemical base under the important clinical distinction between active and latent MTPs. The study by Chen on the use of magnetic resonance elastography (MRE) imaging of the taut band of an MTP in an upper trapezius muscle may open a whole new chapter in the centuries-old search for a convincing demonstration of the cause of MTP symptoms. MRE is a modification of existing magnetic resonance imaging equipment, and it images stress produced by adjacent tissues with different degrees of tension. This report seems to present an MRE image of the taut band that shows the chevron signature of the increased tension of the taut band compared with surrounding tissues.     

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.     

Quantification of changes in myofascial trigger point sensitivity with the pressure algometer following passive stretch

In order to determine the relationship between trigger point sensitivity and the referred symptoms of myofascial pain, VAS ratings of referred pain intensity and pressure algometer measures of myofascial trigger point sensitivity were taken pre and post treatment of the muscle containing the trigger point with passive stretch. The results in 20 subjects, experiencing unilateral or bilateral myofascial head and neck pain, showed that myofascial trigger point sensitivity decreases in response to passive stretch as assessed by the pressure algometer, and that trigger point sensitivity and intensity of referred pain are related.     

Trigger points: diagnosis and management

Trigger points are discrete, focal, hyperirritable spots located in a taut band of skeletal muscle. They produce pain locally and in a referred pattern and often accompany chronic musculoskeletal disorders. Acute trauma or repetitive microtrauma may lead to the development of stress on muscle fibers and the formation of trigger points. Patients may have regional, persistent pain resulting in a decreased range of motion in the affected muscles. These include muscles used to maintain body posture, such as those in the neck, shoulders, and pelvic girdle. Trigger points may also manifest as tension headache, tinnitus, temporomandibular joint pain, decreased range of motion in the legs, and low back pain. Palpation of a hypersensitive bundle or nodule of muscle fiber of harder than normal consistency is the physical finding typically associated with a trigger point. Palpation of the trigger point will elicit pain directly over the affected area and/or cause radiation of pain toward a zone of reference and a local twitch response. Various modalities, such as the Spray and Stretch technique, ultrasonography, manipulative therapy and injection, are used to inactivate trigger points. Trigger-point injection has been shown to be one of the most effective treatment modalities to inactivate trigger points and provide prompt relief of symptoms.     

High-power pain threshold ultrasound technique in the treatment of active myofascial trigger points: a randomized, double-blind, case-control study

OBJECTIVE: To study what effects a high-power, pain-threshold, static ultrasound technique applied to acute myofascial trigger points of the upper trapezius has on pain and on active cervical lateral bending. DESIGN: Double-blind randomized trial. SETTING: Physical therapy unit of a private general hospital. PARTICIPANTS: Seventy-two adults with acute pain on 1 side of the neck, admitted to the outpatient unit during 1999 and 2000. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Visual analog scale and goniometric measurement of active lateral bending of the neck performed daily after treatment sessions and length of treatment (number of therapy sessions). RESULTS: High-power ultrasound applied to the trigger points before stretching the muscle was more effective (P<.05) than conventional ultrasound, and it also significantly (P<.001) decreased the length of therapy. CONCLUSIONS: High-power, pain-threshold, static ultrasound technique may be considered in the treatment of patients with acute myofascial pain syndrome, with the understanding that this technique demands more concentration and communication between the patient and the therapist.     

Electrophysiological characteristics according to activity level of myofascial trigger points

[Purpose] This study compared the differences in electrophysiological characteristics of normal muscles versus muscles with latent or active myofascial trigger points, and identified the neuromuscular physiological characteristics of muscles with active myofascial trigger points, thereby providing a quantitative evaluation of myofascial pain syndrome and clinical foundational data for its diagnosis. [Subjects] Ninety adults in their 20s participated in this study. Subjects were equally divided into three groups: the active myofascial trigger point group, the latent myofascial trigger point group, and the control group. [Methods] Maximum voluntary isometric contraction (MVIC), endurance, median frequency (MDF), and muscle fatigue index were measured in all subjects. [Results] No significant differences in MVIC or endurance were revealed among the three groups. However, the active trigger point group had significantly different MDF and muscle fatigue index compared with the control group. [Conclusion] Given that muscles with active myofascial trigger points had an increased MDF and suffered muscle fatigue more easily, increased recruitment of motor unit action potential of type II fibers was evident. Therefore, electrophysiological analysis of these myofascial trigger points can be applied to evaluate the effect of physical therapy and provide a quantitative diagnosis of myofascial pain syndrome.Key words: Electromyography, Electrophysiological characteristics, Myofascial trigger point