Muscle Pain | Myofascial Pain

Muscle Pain or Myofascial Pain Syndrome

An article by Dr. Hamsa Jayasheel

Introduction:

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.

Etiology:

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.

Pathophysiology:

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.

Clinical features:

• Regional pain in the neck, shoulders, upper limbs, face, low back and lower limbs
• Referred pain
• Burning sensation
• Tenderness of the involved muscle
• Poor sleep
• Swelling
• Fatigue
• Paraesthesia
• Decreased range of motion
• Weakness
• Secondary depression and sleep disturbances

Diagnosis:

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.

Essential criteria:

• Taut band palpable (where the muscle is accessible)
• Exquisite spot of tenderness in a taut band
• Patient recognition of current pain complaint by the pressure of examiner
• Painful limit to full stretch ROM

Confirmatory observations:

• The visual or tactile local twitch response
• Referred pain sensation on compression of the taut band
• SEA confirmed by electromyography

Experimental techniques include:

• Electromyographic demonstration of spontaneous electrical activity characteristic of active loci in the tender nodule of a taut band,
• Needle electromyography,
• IR Spectroscopy, and
• Surface electromyography
• Magnetic resonance elastography
• Sono elastography combined with Doppler imaging

Differential diagnosis:

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

Other differential diagnoses include:

• Muscle spasm
• Neuropathic or radicular pain
• Delayed onset muscle pain
• Articular dysfunction and
• Infectious myositis
• Tension headaches
• Migraine and cluster headaches
• Low back syndromes
• Pelvic pain
• Intermittent claudication
• Bursitis, arthritis, tendinosis

Treatment:

The usual treatment includes

• Medication (painkillers, low dose anti-depressants, anti-epileptics).
• Therapy (stretching, posture training, massage, heat, ultrasound).
• Invasive techniques:
  • Dry needling: When the Trigger point is clearly identified and stabilized between two fingers, a hypodermic needle or acupuncture needle is inserted into the trigger point and repeatedly punctured by withdrawing and re inserting.
  • Trigger point injections: Using the same method as described above, a hypodermic needle is inserted and normal saline or local anaesthetic with or without steroids is injected into and near the trigger points. Contraindications: Anticoagulation, Aspirin ingestion within three days of injection, presence of local or systemic infection, allergy to the drug, extreme fear of needles.
  • Botox inj: In resistant cases, botox injection is done with very good results.