A New Unified Theory of Trigger Point Formation: Failure of Pre- and Post-Synaptic Feedback Control Mechanisms.

The origin of the myofascial trigger point (TrP), an anomalous locus in muscle, has never been well-described. A new trigger point hypothesis (the new hypothesis) presented here addresses this lack. The new hypothesis is based on the concept that existing myoprotective feedback mechanisms that respond to muscle overactivity, low levels of adenosine triphosphate, (ATP) or a low pH, fail to protect muscle in certain circumstances, such as intense muscle activity, resulting in an abnormal accumulation of intracellular Ca2+, persistent actin-myosin cross bridging, and then activation of the nociceptive system, resulting in the formation of a trigger point. The relevant protective feedback mechanisms include pre- and postsynaptic sympathetic nervous system modulation, modulators of acetylcholine release at the neuromuscular junction, and mutations/variants or post-translational functional alterations in either of two ion channelopathies, the ryanodine receptor and the potassium-ATP ion channel, both of which exist in multiple mutation states that up- or downregulate ion channel function. The concepts that are central to the origin of at least some TrPs are the failure of protective feedback mechanisms and/or of certain ion channelopathies that are new concepts in relation to myofascial trigger points.

Foci of Segmentally Contracted Sarcomeres in Trapezius Muscle Biopsy Specimens in Myalgic and Nonmyalgic Human Subjects: Preliminary Results.

OBJECTIVE: The myofascial trigger point hypothesis postulates that there are small foci of contracted sarcomeres in resting skeletal muscle. Only one example, in canine muscle, has been published previously. This study evaluated human muscle biopsies for foci of contracted sarcomeres. SETTING: The Departments of Rehabilitation Sciences and Physiotherapy at Ghent University, Ghent, Belgium. SUBJECTS: Biopsies from 28 women with or without trapezius myalgia were evaluated, 14 in each group. METHODS: Muscle biopsies were obtained from regions of taut bands in the trapezius muscle and processed for light and electron microscopy and for histochemical analysis. Examination of the biopsies was blinded as to group. RESULTS: A small number of foci of segmentally contracted sarcomeres were identified. One fusiform segmental locus involved the entire muscle fiber in tissue from a myalgic subject. Several transition zones from normal to contracted sarcomeres were found in both myalgic and nonmyalgic subjects. The distance between Z-lines in contracted sarcomeres was about 25-45% of the same distance in normal sarcomeres. Z-lines were disrupted and smeared in the contracted sarcomeres. CONCLUSIONS: A small number of foci of segmentally contracted sarcomeres were found in relaxed trapezius muscle in human subjects, a confirmation of the only other example of spontaneous segmental contraction of sarcomeres (in a canine muscle specimen), consistent with the hypothesis of trigger point formation and with the presence of trigger point end plate noise.

Myofascial Trigger Point Pain Syndromes.

Myofascial pain syndromes caused by trigger points (TrPs) in muscle are a common cause of local and generalized pain. Trigger points are hyperirritable zones in contracted bands of muscle, thought to be caused by muscle overload or stress. Stress TrPs have characteristic electromyographic features, and can be visualized with ultrasound and magnetic resonance elastography. Trigger point needling or injection can be effective in inactivating TrP, but correcting triggers is also critical.

Myofascial Pain Syndrome: A Nociceptive Condition Comorbid with Neuropathic or Nociplastic Pain.

Myofascial pain syndrome is featured by the presence of myofascial trigger points (TrPs). Whether TrPs are primary or secondary phenomena or if they relate to central or peripheral nervous system disorders is controversial. Referred pain, a cardinal sign of TrPs, is a central phenomenon driven by peripheral input. In 2021, the International Association for the Study of Pain (IASP) proposed a clinical criteria and grading system for classifying patients with pain on nociceptive, neuropathic, or nociplastic phenotypes. Myofascial TrP pain has been traditionally categorized as a nociceptive phenotype; however, increasing evidence supports that this condition could be present in patients with predominantly nociplastic pain, particularly when it is associated with an underlying medical condition. The clinical response of some therapeutic approaches for managing TrPs remains unclear. Accordingly, the ability to classify myofascial TrP pain into one of these phenotypes would likely be critical for producing more successful clinical treatment outcomes by a precision medicine approach. This consensus paper presents evidence supporting the possibility of subgrouping individuals with myofascial TrP pain into nociceptive, nociplastic, or mixed-type phenotype. It is concluded that myofascial pain caused by TrPs is primarily a nociceptive pain condition, is unlikely to be classified as neuropathic or nociplastic, but can be present in patients with predominantly neuropathic or nociplastic pain. In the latter cases, management of the predominant central pain problem should be a major treatment goal, but the peripheral drive from TrPs should not be ignored, since TrP treatment has been shown to reduce sensitization-associated symptomatology in nociplastic pain conditions, e.g., fibromyalgia.

Contracture Knots vs. Trigger Points. Comment on Ball et al. Ultrasound Confirmation of the Multiple Loci Hypothesis of the Myofascial Trigger Point and the Diagnostic Importance of Specificity in the Elicitation of the Local Twitch Response. Diagnostics 2022, 12, 321.

A recent study published in Diagnostics attempted to visualize trigger points and contracture knots with high-definition ultrasound. Based on their findings, the authors reversed the commonly understood meaning of the two terms. However, they did so without providing any convincing evidence. The authors maintained that their sonography images represented trigger points within contracture knots, supporting the multiple loci hypothesis. On review of the paper, both conclusions seem premature and rather speculative.

International, multidisciplinary Delphi consensus recommendations on non-pharmacological interventions for fibromyalgia.

OBJECTIVES: To develop evidence-based expert recommendations for non-pharmacological treatments for pain, fatigue, sleep problems, and depression in fibromyalgia. METHODS: An international, multidisciplinary Delphi exercise was conducted. Authors of EULAR and the Canadian Fibromyalgia Guidelines Group, members of the American Pain Society and clinicians with expertise in fibromyalgia were invited. Participants were asked to select non-pharmacological interventions that could be offered for specific fibromyalgia symptoms and to classify them as either core or adjunctive treatments. An evidence summary was provided to aid the decision making. Items receiving >70% votes were accepted, those receiving <30% votes were rejected and those obtaining 30-70% votes were recirculated for up to two additional rounds. RESULTS: Seventeen experts participated (Europe (n = 10), North America (n = 6), and Israel (n = 1)) in the Delphi exercise and completed all three rounds. Aerobic exercise, education, sleep hygiene and cognitive behavioural therapy were recommended as core treatments for all symptoms. Mind-body exercises were recommended as core interventions for pain, fatigue and sleep problems. Mindfulness was voted core treatment for depression, and adjunctive treatment for other symptoms. Other interventions, namely music, relaxation, hot bath, and local heat were voted as adjunctive treatments, varying between symptoms. CONCLUSIONS: This study provided evidence-based expert consensus recommendations on non-pharmacological treatments for fibromyalgia that may be used to individualise treatments in clinical practice targeting the diverse symptoms associated with fibromyalgia.

Trigger point injections for chronic non-malignant musculoskeletal pain: a systematic review.

OBJECTIVE: This systematic review assessed the available published evidence on the efficacy and safety of using trigger point injection (TPI) to treat patients with chronic non-malignant musculoskeletal pain that had persisted for at least 3 months. METHODS: All published systematic reviews or randomized controlled trials detailing the use of TPI in patients with chronic, non-malignant musculoskeletal pain (persisting for >3 months) were identified by systematically searching literature databases and the Websites of various health technology assessment agencies, research registers, and guidelines sites up to July 2006. RESULTS: Although no systematic reviews were identified, 15 peer-reviewed randomized controlled trials met the inclusion criteria. However, deficiencies in reporting, small sample sizes, and marked inter-study heterogeneity precluded a definitive synthesis of the data. TPI is a safe procedure when used by clinicians with appropriate expertise and training. It relieved symptoms when used as a sole treatment for patients with chronic head, neck, shoulder, and back pain or whiplash syndrome, regardless of the injectant used, and may be a useful adjunct to intra-articular injection in the treatment of osteoarthritis pain. Although the addition of TPI to stretching exercises augments treatment outcomes, this was also true of other therapies such as ultrasound and laser. CONCLUSION: The efficacy of TPI is no more certain than it was a decade ago as, overall, there is no clear evidence of either benefit or ineffectiveness. The only advantage of injecting anesthetic into trigger points may be to reduce the pain of the needling process, which may not be an insignificant benefit.

Referred pain elicited by manual exploration of the lateral rectus muscle in chronic tension-type headache.

OBJECTIVE: To analyze the presence of referred pain elicited by manual examination of the lateral rectus muscle in patients with chronic tension-type headache (CTTH). DESIGN: A case-control blinded study. SETTING: It has been found previously that the manual examination of the superior oblique muscle can elicit referred pain to the head in some patients with migraine or tension-type headache. However, a referred pain from other extraocular muscles has not been investigated. METHODS: Fifteen patients with CTTH and 15 healthy subjects without headache history were included. A blinded assessor performed a manual examination focused on the search for myofascial trigger points (TrPs) in the right and left lateral rectus muscles. TrP diagnosis was made when there was referred pain evoked by maintained pressure on the lateral corner of the orbit (anatomical projection of the lateral rectus muscle) for 20 seconds, and increased referred pain while the subject maintained a medial gaze on the corresponding side (active stretching of the muscle) for 15 seconds. On each side, a 10-point numerical pain rate scale was used to assess the intensity of referred pain at both stages of the examination. RESULTS: Ten patients with CTTH (66.6%) had referred pain that satisfied TrPs diagnostic criteria, while only one healthy control (0.07%) reported referred pain upon the examination of the lateral rectus muscles (P < 0.001). The elicited referred pain was perceived as a deep ache located at the supraorbital region or the homolateral forehead. Pain was evoked on both sides in all subjects with TrPs, with no difference in pain intensity between the right and the left. The average pain intensity was significantly greater in the patient group (P < 0.001). All CTTH patients with referred pain recognized it as the frontal pain that they usually experienced during their headache attacks, which was consistent with active TrPs. CONCLUSION: In some patients with CTTH, the manual examination of lateral rectus muscle TrPs elicits a referred pain that extends to the supraorbital region or the homolateral forehead. Nociceptive inputs from the extraocular muscles may sustain the activation of trigeminal neuron, thus sensitizing central pain pathways and exacerbating headache.

Post-needling soreness after myofascial trigger point dry needling: Current status and future research.

Post-dry needling soreness is a common complication of myofascial trigger point (MTrP) dry needling treatment. The prevention, management and relevance of this complication remain uncertain. This paper examines the current state of knowledge and suggests directions for further studies in this area. MTrPs are hypersensitive nodules in skeletal muscles' taut bands, present in several pain conditions. Dry needling has been recommended for relieving MTrP pain. MTrP dry needling procedures have shown to be associated with post-needling soreness, which is thought to be a consequence of the neuromuscular damage, and hemorrhagic and inflammatory reaction generated by the needle. Postneedling soreness is a very frequent effect after deep dry needling, usually lasting less than 72 h. It may not be especially distressing for most patients. However, patients presenting with higher levels of post-needling soreness, not perceiving dry needling effectiveness in the first session, or not having high myofascial pain intensity before treatment, could be the most likely to find post-needling soreness more distressing, functionally limiting and to abandon treatment. Future research should assess the clinical relevance of post-needling soreness. Post-needling soreness should be considered when investigating dry needling effectiveness since it could overlie the original myofascial pain and influence the patients' pain ratings.

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.

A review of myofascial pain and fibromyalgia--factors that promote their persistence.

Chronic muscle pain (myalgia) is a common problem throughout the world. Seemingly simple, it is actually a difficult problem for the clinician interested in determining the aetiology of the pain, as well as in managing the pain. The two common muscle pain conditions are fibromyalgia and myofascial pain syndrome. Fibromyalgia is a chronic, widespread muscle tenderness syndrome, associated with central sensitisation. It is often accompanied by chronic sleep disturbance and fatigue, visceral pain syndromes like irritable bowel syndrome and interstitial cystitis. Myofascial pain syndrome is an overuse or muscle stress syndrome characterised by the presence of trigger points in muscle. The problem these syndromes pose lies not in making the diagnosis of muscle pain. Rather, it is the need to identify the underlying cause(s) of persistent or chronic muscle pain in order to develop a specific treatment plan. Chronic myalgia may not improve until the underlying precipitating or perpetuating factor(s) are themselves managed. Precipitating or perpetuating causes of chronic myalgia include structural or mechanical causes like scoliosis, localised joint hypomobility, or generalised or local joint laxity; and metabolic factors like depleted tissue iron stores, hypothyroidism or Vitamin D deficiency. Sometimes, correction of an underlying cause of myalgia is all that is needed to resolve the condition.

A critical evaluation of Quintner et al: missing the point.

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

Diagnosis of myofascial pain syndrome.

Myofascial pain is one of the most common causes of pain. The diagnosis of myofascial pain syndrome (MPS) is made by muscle palpation. The source of the pain in MPS is the myofascial trigger point, a very localized region of tender, contracted muscle that is readily identified by palpation. The trigger point has well-described electrophysiologic properties and is associated with a derangement of the local biochemical milieu of the muscle. A proper diagnosis of MPS includes evaluation of muscle as a cause of pain, and assessment of associated conditions that have an impact on MPS.