Muscle pain or myofascial pains are often defined as “pain related to inflammation or irritation of muscle or of the fascia surrounding the muscle”. Myofascial pain syndrome (MPS) is a very common clinical condition there is muscle pain with sensory, motor and autonomic symptoms associated myofascial trigger points.
MPS is a soft tissue pain syndrome where the pain is present primarily at a single area or quadrant of the body, as compared to other soft tissue pain syndromes, like chronic fatigue syndrome, hypermobility syndrome, or fibromyalgia, where the pain is generalized. MFS often can be acute or chronic.
A myofascial trigger point is defined as a hyperirritable spot, usually within a taut band of skeletal muscle which is painful on compression or deep palpation and should produce to characteristic pain, motor dysfunction and autonomic phenomena.
Trigger points are classified as
• Active- Causes pain at rest, tender to palpate with a referred pain pattern or
• Latent- Doesn’t cause pain at rest but may restrict movement or cause muscle weakness and tenderness on palpation.
Psychological stress, muscle tension and physical factors like poor posture can cause a latent trigger point to become active, causing the pain.
The cause of the event of the trigger point is still unclear. Taught bands are the precursors of trigger points. They can occur commonly in asymptomatic individuals too. Injury to the muscles due to acute trauma or repetitive microtrauma can lead to the initiation of a trigger point. Lack of exercise, prolonged poor posture, vitamin deficiencies, sleep disturbances and joint problems from sustained muscle contractions all contribute to microtrauma.
Several mechanisms are hypothesized to elucidate this motor abnormality, the foremost accepted one is that the “Integrated Hypothesis” first developed by Simmons and later expanded by Gerwin.
Simmons’ integrated hypothesis may be a six-link chain that starts with the abnormal release of acetylcholine as shown below in the flowchart.
Gerwin added more specific details stating that sympathetic nervous system activity augments acetylcholine release associated with local hypoperfusion caused by the contraction (taut band) which results in muscle ischemia and hypoxia leading to acidification of tissue.
The prolonged ischemia also leads to muscle injury resulting in the discharge of potassium, bradykinins, cytokines, ATP, and substance P which could stimulate nociceptors within the muscle leading to tenderness and pain observed in myofascial trigger points.
Depolarization of nociceptive neurons causes the discharge of calcitonin gene-related peptide (CGRP). CGRP inhibits acetylcholine esterase, increases the sensitivity of acetylcholine receptors, and releases acetylcholine leading to SEA.
In recent studies by Shah et al using microdialysis techniques confirmed the presence of those substances at trigger point sites. Elevations of substance P, protons (H+), CGRP, bradykinin, serotonin, norepinephrine, TNF, interleukins, and cytokines were found in active trigger points compared to normal muscle or even latent trigger points. The pH of the active trigger point region decreases up to pH 4 (whereas normal pH value is 7.4) causing muscle pain and tenderness also as a decrease in acetylcholine esterase activity leading to sustained muscle contractions.
There is no specific laboratory test, imagining study, or interventional modality to diagnose trigger points.
Palpation is the most important findings in identifying the presence of taut bands in muscle. The examiner needs a detailed knowledge of muscle anatomy, the direction of specific muscle fibers, and muscle function
Two techniques of palpation: Flat palpation technique and Pincer palpation technique.
The palpation on muscle must be done in proper ways and confirmatory observations to identify the presence of trigger points.
Experimental techniques include:
Fibromyalgia is the most confusing as both cause severe muscle pain and tenderness but they do not share the same etiology or pathogenesis and their clinical presentation is not the same.
The main differences are
|Local or regional Pain, no systemic illness||Widespread Pain with psychological symptoms, sleep disturbances & systemic illness|
|Regional Condition||Bilateral as well as axial Pain|
|Presence of Taut Band||Absence of taut bands|
|Referred Pain||Presence of at least 11 tender points|
Other differential diagnoses include:
The usual treatment includes