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.     

Inhibitory effect of dry needling on the spontaneous electrical activity recorded from myofascial trigger spots of rabbit skeletal muscle

OBJECTIVE: Dry needling of myofascial trigger points can relieve myofascial pain if local twitch responses are elicited during needling. Spontaneous electrical activity (SEA) recorded from an active locus in a myofascial trigger point region has been used to assess the myofascial trigger point sensitivity. This study was to investigate the effect of dry needling on SEA. DESIGN: Nine adult New Zealand rabbits were studied. Dry needling with rapid insertion into multiple sites within the myofascial trigger spot region was performed to the biceps femoris muscle to elicit sufficient local twitch responses. Very slow needle insertion with minimal local twitch response elicitation was conducted to the other biceps femoris muscle for the control study. SEA was recorded from 15 different active loci of the myofascial trigger spot before and immediately after treatment for both sides. The raw data of 1-sec SEA were rectified and integrated to calculate the average integrated value of SEA. RESULTS: Seven of nine rabbits demonstrated significantly lower normalized average integrated value of SEA in the treatment side compared with the control side (P < 0.05). The results of two-way analysis of variance show that the mean of the normalized average integrated value of SEA in the treatment group (0.565 +/- 0.113) is significantly (P < 0.05) lower than that of the control (0.983 +/- 0.121). CONCLUSIONS: Dry needling of the myofascial trigger spot is effective in diminishing SEA if local twitch responses are elicited. The local twitch response elicitation, other than trauma effects of needling, seems to be the primary inhibitory factor on SEA during dry needling.     

Effects of a calcium channel blocker on electrical activity in myofascial trigger spots of rabbits

OBJECTIVE: This study investigated the effect of a calcium channel blocking agent, verapamil, on the spontaneous electrical activity (SEA) in a myofascial trigger spot of biceps femoris muscles of rabbits. DESIGN: Left and right legs of eight adult New Zealand rabbits were randomly assigned into either experimental or control groups to assess the effect of verapamil on SEA. Verapamil and normal saline were injected into the external iliac artery for experimental and control groups, respectively. The experiment was divided into two phases: Phase A investigated the immediate effect of verapamil on SEA of one active locus, and phase B studied the effect of verapamil on SEA of 25 different active loci. The average integrated value of SEA was used to statistically analyze the effect of verapamil on myofascial trigger-spot sensitivity. RESULTS: In phase A, conducted on one active locus, the regression analysis results showed that the average integrated value in the verapamil group linearly decreased with time, but the average integrated value did not significantly change with time in the control group. In phase B, which analyzed 25 different active loci, the results indicated that the mean average integrated values in the verapamil group was significantly lower than that of the control group. CONCLUSIONS: Calcium channel blockers can effectively inhibit the SEA of myofascial trigger spots.     

Shock waves as treatment of mouse myofascial trigger points

Introduction

An abnormal increase in spontaneous neurotransmission can induce subsynaptic knots in the myocyte called myofascial trigger points. The treatment of choice is to destroy these trigger points by inserting needles. However, 10% of the population has a phobia of needles, blood, or injuries. Therefore, the objective of this study is to verify the usefulness of shock waves in the treatment of myofascial trigger points.

Methods

Two groups of mice have been developed for this: healthy muscles treated with shock waves; trigger points affected muscles artificially generated with neostigmine and subsequently treated with shock waves. Muscles were stained with methylene blue, PAS-Alcian Blue, and labeling the axons with fluorescein and the acetylcholine receptors with rhodamine. Using intracellular recording the frequency of miniature endplate potentials (mEPPs) was recorded and endplate noise was recorded with electromyography.

Results

No healthy muscles treated with shock waves showed injury. Twitch knots in mice previously treated with neostigmine disappeared after shock wave treatment. Several motor axonal branches were retracted. On the other hand, shock wave treatment reduces the frequency of mEPPs and the number of areas with endplate noise.

Discussion

Shock waves seem to be a suitable treatment for myofascial trigger points. In the present study, with a single session of shock waves, very relevant results have been obtained, both functional (normalization of spontaneous neurotransmission) and morphological (disappearance of myofascial trigger points). Patients with a phobia of needles, blood, or injuries who cannot benefit from dry needling may turn to noninvasive radial shock wave treatment.     

The spinal cord connections of the myofascial trigger spots.

BACKGROUND: Recent electrophysiological studies revealed that endplate noise (EPN) could be specifically recorded from a myofascial trigger point (MTrP) region. EPN has been considered as the focal graded potentials due to excessive acetylcholine release in neuromuscular junction. A recent histological study has demonstrated a free nerve ending at the vicinity of the site, from where EPN could be recorded in an MTrP region. However, the sensory (afferent) and the motor (efferent) connections between an MTrP and the spinal cord still has never been fully studied. AIMS: The aim of this study was to delineate both motor and sensory connections between an MTrP and the spinal cord by applying the stain with horseradish peroxidase (HRP). METHODS: Nine Wistar rats were studied. When the rat was anesthetized, its biceps femoris muscles were exposed for localizing the myofascial trigger spot (MTrS, equivalent to MTrP in human). In one side, a monopolar Teflon-coated, hollow-needle electrode was used for searching EPN in an MTrS region, and then HRP was injected via this hollow-needle electrode into the site where EPN was recorded. HRP was also injected into a normal (non-taut band, non-MTrS) site in the contralateral side to obtain the control data. Two days after HRP injection, the rats were sacrificed and their spinal cords and dorsal root ganglia (DRG) were sectioned for the identification of the sites where neurons were labeled with HRP. RESULTS: The HRP-labeled neurons were found in the ventral horn of the spinal cord and in the DRG over L3, L4, and L5, while most were found in the L5 level. The mean numbers of HRP-labeled neurons in the EPN side looked smaller than that in the control side, but the difference did not reach statistically significant level (P>0.05). The mean values of the diameters of the HRP-labeled neurons in the DRG were not significantly different between the EPN side and the control side (P>0.05). However, HRP-neurons in the ventral horn of the spinal cord in the EPN side showed mild tendency to be smaller than that in the control side. CONCLUSIONS: The spinal cord connections of an MTrS are basically similar to that for a normal tissue region. The motor neurons related to MTrS tended to be smaller in their diameters. The findings in this study further supported the previously proposed hypotheses for the pathogenesis of an MTrP.     

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.     

Ultrasound Imaging of Injections in Masseter Muscle without Contrast Agent Using Strain Elastography and a Novel B-Mode Spatiotemporal Filter

Botulinum toxin type A (BTX-A) injections in masseter muscle can alleviate muscle tightness and aching pain caused by idiopathic masticatory myalgia, a subform of the myofascial pain syndrome. Yet the injection procedure (number, amount) is currently empirical. In this ex vivo study, we determined the feasibility of using contrast-free ultrasound imaging to visualize the short-term injectate propagation. Ultrasound annotations of BTX-A injectate spread in N = 12 porcine masseter muscles were compared with the histopathology of the excised masseter. BTX-A presence was automatically detected in the ultrasound cine by: compensating tissue motion and deformation during injection with a novel spatiotemporal filtering (SF) algorithm, and by imaging tissue swelling strains with strain elastography (SE). BTX-A injectate introduced 6.5% (standard deviation = 5.0%) echogenicity contrast and 13.9% (standard deviation = 3.7%) tissue swelling strain. Muscle fasciae were a border for BTX-A distribution. The SF algorithm achieved significantly higher noise rejection (contrast-to-noise ratio = 4.63) than SE (2.56, p = 0.01), and state-of-the-art 2-D digital image correlation (1.81, p < 0.001) and direct image subtraction (1.29, p < 0.001) methods. Histopathology agreed well with ultrasound (Dice coefficient = 0.48), with deviations mainly explained by the three-dimensional inhomogeneous distribution of BTX-A. Preliminary in vivo patient results indicated that SF and SE discard artifactual BTX-A detection outside the injection region. The proposed methods contribute to objectivize ultrasound-guided injections, with additional applications, for instance, to monitor injectate spread of local anesthetics.     

Comparison of the prevalence of myofascial trigger points of muscles acting on knee between patients with moderate degree of knee osteoarthritis and healthy matched people

IntroductionTrigger points have been implicated in the development of several musculoskeletal disorders. Trigger points harbored in lower limb muscles might represent a ubiquitous source of pain in patients with knee osteoarthritis (OA). This study was carried out to evaluate the prevalence of Myofascial Trigger Points (MTrPs) in muscles acting on the knee in patients with OA.MethodsThirty-seven patients aged at least 55 years old with a moderate degree of OA (grade III of Kellgren and Lawrence scale) were recruited. Thirty asymptomatic people, matched on age and body mass index, were considered as the control group. Ten muscles acting on the knee joint were selected. Taut bands were also identified using a skin rolling method. A pressure of 3 kg/cm² was used to identify myofascial trigger points in all muscles except the popliteus (8 kg/cm²).ResultsChi-square was performed to compare the prevalence of trigger points between the groups. The McNemar test was administered to compare the prevalence of trigger points in the right and left sides of participants. Prevalence of the trigger points was significantly higher in patients with knee OA compared with asymptomatic people in all muscles except for right (p = 0.17) and left (p = 0.41) rectus femoris, right (p = 0.61) and left (p = 0.22) sartorius and left biceps femoris (p = 0.08). Comparison of the prevalence of MTrPs bilaterally revealed that only the right and left sartorius differed significantly (p = 0.008).ConclusionsThe prevalence of MTrPs in the muscles acting on the knee joint is higher in patients with a moderate degree of knee OA compared with asymptomatic subjects.     

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.      

Intramuscular and nerve root stimulation vs lidocaine injection to trigger points in myofascial pain syndrome.

OBJECTIVES: To compare the efficacies of an intramuscular stimulation technique and 0.5% lidocaine injection to trigger points in myofascial pain syndrome. PARTICIPANTS: Forty-three people with myofascial pain syndrome of the upper trapezius muscle. INTERVENTIONS: Twenty-two subjects were treated with intramuscular stimulation and another 21 with 0.5% lidocaine injection at all the trigger points on days 0, 7 and 14. RESULTS: Intramuscular stimulation resulted in a significant reduction in Wong-Baker FACES pain scale scores at all visits and was more effective than trigger point injection. Intramuscular stimulation also resulted in significant improvement on the Geriatric Depression Scale - Short Form. Local twitch responses occurred in 97.7% (42/43) of patients. All the passive cervical ranges of motion were significantly increased. Post-treatment soreness was noted in 54.6% of patients in the intramuscular stimulation group and 38.1% in the trigger point injection group, respectively, and gross subcutaneous haemorrhage (> 4 cm2) was seen in only one patient in the trigger point injection group. CONCLUSION: In managing myofascial pain syndrome, after one month intramuscular stimulation resulted in more significant improvements in pain intensity, cervical range of motion and depression scales than did 0.5% lidocaine injection of trigger points. Intramuscular stimulation is therefore recommended for myofascial pain syndrome.     

Botulinum Toxin Dilution and Endplate Targeting in Spasticity: A Double-Blind Controlled Study

Gracies J-M, Lugassy M, Weisz DJ, Vecchio M, Flanagan S, Simpson DM. Botulinum toxin dilution and endplate targeting in spasticity: a double-blind controlled study.

Objective

To determine the effects of botulinum neurotoxin type A (BTX-A) dilution and endplate-targeting in spastic elbow flexors.

Design

Double blind randomized controlled trial; 4-month follow-up after a 160-unit injection of BTX-A into spastic biceps brachii (4 sites). Randomization into: group 1: 100 mouse units (MU)/mL dilution, 0.4cc/site, 4-quadrant injection; group 2: 100MU/mL dilution, 0.4cc/site, 4 sites along endplate band; group 3: 20MU/mL dilution, 2cc/site, 4-quadrant injection (n=7 per group).

Setting

Institutional tertiary care ambulatory clinic.

Participants

Referred sample of 21 adults with spastic hemiparesis. No participant withdrew due to adverse effects.

Intervention

A 160-unit injection of BTX-A of different dilutions and locations into biceps brachii.

Main Outcome Measures

Primary: agonist and antagonist (cocontraction) mean rectified voltage (MRV) of elbow flexors/extensors during maximal isometric flexion/extension; secondary: maximal voluntary power of elbow flexion/extension; spasticity angle and grade in elbow flexors/extensors (Tardieu Scale); active range of elbow extension/flexion.

Results

BTX-A injection overall reduced agonist flexor MRV (-47.5%, P<0.0001), antagonist flexor MRV (-12%, P=.037), antagonist extensor MRV (-19%, P<.01), flexion maximal voluntary power (-33%, P<.001), elbow flexor spasticity angle (-30%, P<.001) and grade (-17%, P=.03), and increased extension maximal voluntary power (24%, P=.037) and active range of elbow extension (5.5%, 8°, P=.002). Agonist and antagonist flexor MRV reductions in group 3 (-81% and -31%) were greater than in groups 1 and 2, whereas increase in active range of elbow extension was greater in group 2 (10%) than in groups 1 and 3 (P<.05, analysis of covariance [ANCOVA]). Elbow flexor spasticity was significantly reduced in groups 2 and 3 only (P<.05, ANCOVA).

Conclusions

In spastic biceps, high-volume or endplate-targeted BTX-A injections achieve greater neuromuscular blockade, cocontraction and spasticity reduction, and active range of elbow extension improvement, than low volume, nontargeted injections.     

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.     

The effect of small doses of botulinum toxin a on neck-shoulder myofascial pain syndrome: a double-blind, randomized, and controlled crossover trial

OBJECTIVES: Myofascial pain syndrome is a common cause of muscular pain in the shoulder-neck region. Injections of large amounts of botulinum toxin A have been found to be beneficial for the alleviation of myofascial pain, but large doses of this toxin may cause paresis of the muscle and other adverse events. The aim of this work was to determine the effect of small doses (5 U) of botulinum toxin A (BTA) injected directly into the painful trigger points of the muscles, using a double-blind crossover technique. METHODS: On the basis of the empirical criteria proposed for diagnosis of myofascial pain syndrome, 31 patients suffering from myofascial pain in the neck-shoulder region were studied. The patients received either botulinum toxin A or physiological saline injections on 2 occasions 4 weeks apart. The total dose varied from 15 to 35 U of botulinum toxin A [28+/- 6 U (mean+/- SD)]. The follow-up measurements were carried out at 4 weeks after each treatment. Neck pain and result of treatment were assessed with questionnaires. The pressure pain threshold was determined using a dolorimeter. RESULTS: Neck pain values decreased from 4.3+/- 2.4 to 3.3+/- 2.0 after saline injections and from 4.1+/- 2.1 to 3.3+/- 2.2 after botulinum toxin A. The pressure pain threshold values increased from 5.2+/-1.6 to 5.9+/-1.5 and from 5.7+/-1.6 to 5.9+/-1.6 after injections with saline and botulinum toxin A, respectively. No statistically significant changes in the neck pain and pressure pain threshold values occurred between the botulinum toxin A and saline groups. After the first injections, the subjective result of treatment was significantly (P=0.008) in favor of botulinum toxin A, and after the second injections, the subjective result was better for saline, but the difference was not statistically significant (P=0.098). There was no significant difference in the prevalence of side effects between saline and botulinum toxin A. CONCLUSIONS: Our study shows that there was no difference between the effect of small doses of botulinum toxin A and those of physiological saline in the treatment of myofascial pain syndrome.     

肌筋膜疼痛触发点内理化环境的改变及其作用

背景:以往研究对肌筋膜疼痛触发点的研究主要集中在发病特点和临床治疗方面,有关肌筋膜疼痛触发点局部组织的理化环境变化及其作用的研究较少.目的:总结并讨论肌筋膜疼痛触发点局部组织的理化环境变化及各种理化因子在肌筋膜疼痛中的作用.方法:由第一作者用计算机检索中国期刊全文数据库(CNKI:2000/2010)和Medline数据库(2000/2010),检索词分别为"肌筋膜疼痛触发点、致痛因子、神经系统致敏、伤害性感受器"和"myofascial trigger points,algogenic substance,nervous system sensitization,nociceptors".共检索到159篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章.从肌筋膜疼痛触发点局部理化环境变化及各种理化因子的作用两方面进行总结,对理化环境在肌筋膜疼痛触发点发病中的重要作用进行介绍.结果与结论:肌筋膜疼痛触发点局部肌肉组织各种理化因子发生显著性变化,表现为各神经血管反应物质增多,炎症递质和致痛因子浓度明显升高.但是国内外对肌筋膜疼痛触发点理化环境变化及其作用的相关研究较少,了解仍不深入.     

Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle

Hsieh Y-L, Chou L-W, Joe Y-S, Hong C-Z. Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle.

Objective

To elucidate the neural mechanisms underlying the remote effects produced by dry needling rabbit skeletal muscle myofascial trigger spots (MTrSs) via analyses of their endplate noise (EPN) recordings.

Design

Experimental animal controlled trial.

Setting

An animal laboratory of a university.

Animals

Male New Zealand rabbits (N=96) (body weight, 2.5–3.0kg; age, 16–20wk).

Intervention

Animals received no intervention for neural interruption in group I, transection of the tibial nerve in group II, transection of L5 and L6 spinal cord in group III, and transection of the T1 and T2 spinal cord in group IV. Each group was further divided into 4 subgroups: animals received ipsilateral dry needling, contralateral dry needling, ipsilateral sham needling, or contralateral sham needling of gastrocnemius MTrSs.

Main Outcome Measures

EPN amplitudes of biceps femoris (BF) MTrSs.

Results

BF MTrS mean EPN amplitudes significantly increased (P<.05) initially after gastrocnemius verum needling but reduced to a level significantly lower (P<.05) than the preneedling level in groups I and IV with ipsilateral dry needling or contralateral dry needling, and in group II with contralateral dry needling (but not ipsilateral dry needling). No significant EPN amplitude changes were observed in BF MTrS in group III or in the control animals receiving superficial needling (sham).

Conclusion

This remote effect of dry needling depends on an intact afferent pathway from the stimulating site to the spinal cord and a normal spinal cord function at the levels corresponding to the innervation of the proximally affected muscle.     

Myofascial disorders in the trochlear region in unilateral migraine: a possible initiating or perpetuating factor

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.     

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.     

The effects of myofascial trigger point injections are naloxone reversible

Ten patients with myofascial trigger point pain were entered into a double-blind cross-over study of the reversibility of myofascial trigger point injection (TPI) effects with naloxone versus placebo in order to test the hypothesis that the benefits of TPI are mediated, at least in part, through activation of an endogenous opioid system. Injection of trigger points with 0.25% bupivacaine decreased pain in all subjects and increased range of motion in subjects who, on initial assessment, demonstrated limitations of movement of the affected part(s). Allodynia and palpable bands preceding TPI when present also showed reduction after TPI. All improvements afforded by TPI were significantly reversed with intravenous naloxone (10 mg) compared to intravenous placebo. These results demonstrate a naloxone-reversible mechanism in TPI therapy. This suggests an endogenous opioid system as a mediator for the decreased pain and improved physical findings following injection of myofascial trigger points with local anesthetic.     

Electrophysiological assessment of acupuncture points

OBJECTIVE: This study was designed to assess the occurrence of end plate noise (EPN) in an acupuncture point (AcP). DESIGN: Ten male and 10 female normal volunteers were included in this study. For each subject, mapping of the distribution of EPN loci in an AcP region of Stomach-36 in one leg selected randomly, and also in a nearby non-AcP region in the other leg as a control, was performed with electromyographic recordings. RESULTS: There were significantly more EPN loci in the AcP region of Stomach-36 than in the non-AcP region near this AcP. Whenever the searching needle approached an EPN locus, the subjects always felt pain, soreness, or an unpleasant sensation. This feeling was rarely reported when no EPN was recorded from any site in either an AcP region or a non-AcP region. After electromyographic study, every AcP was confirmed as a myofascial trigger point. CONCLUSIONS: Similar to the distribution of EPN loci in an MTrP region, significantly more EPN loci can be identified in an AcP region of Stomach-36 than in a nearby non-AcP site. This study provides additional support to the hypothesis that some AcPs are also myofascial trigger points.     

Botulinum toxin A versus bupivacaine trigger point injections for the treatment of myofascial pain syndrome: a randomised double blind crossover study

The treatment of myofascial pain syndrome (MPS) is diverse and includes trigger point injections of various substances including local anesthetics, steroids and Botulinum toxin A (BTX A). The purpose of this study was to compare the effectiveness of trigger point injections using BTX A versus bupivacaine, both in combination with a home-based rehabilitation program. To be enrolled, subjects first had to demonstrate responsiveness to bupivacaine trigger point injection. In this single center, double blind, randomized, cross-over trial, 18 patients with MPS received trigger point injections of either 25 units Botulinum toxin A or 0.5 ml of 0.5% bupivacaine per trigger point. A maximum of eight trigger points were injected per subject. Subjects were followed until their pain returned to 75% or more of their pre-injection pain for two consecutive weeks, after which there was a 2 week wash-out period. The subjects then crossed over and had the same trigger points injected with the other agent. All subjects participated in a home exercise program involving static stretches of the affected muscles. Both treatments were effective in reducing pain when compared to baseline (P=0.0067). There was, however, no significant difference between the BTX A and 0.5% bupivacaine groups in duration or magnitude of pain relief, function, satisfaction or cost of care (cost of injectate excluded). Considering the high cost of BTX A, bupivacaine is deemed a more cost-effective injectate for MPS.