Differential diagnosis of trigger points

Objective: A number of medical and structural conditions produce muscular pain associated with myofascial trigger points [TrPs]. These conditions should be considered when evaluating a patient with muscle pain. Thesis: Myofascial pain syndrome is characterized by regional or widespread myalgia with muscle TrPs. Trigger points are also common in fibromyalgia. The TrP is a physical sign that occurs in a variety of myalgic conditions. Acute or chronic muscle stress creates an "energy crisis" that can result in a TrP. A muscle-related nociceptive stimulation of the peripheral and central nervous system results in hypersensitivity. Both mechanical and systemic medical disorders stress muscle. Mechanical problems can be structural or postural. Static [postural] or acute [trauma] muscle overload occurs in mechanical disorders which results in physical and biochemical changes including hypoxia and ischemia, and neuromuscular junction dysfunction. Delayed onset muscle pain is seen in unaccustomed eccentric exercise. Post-laminectomy and failed spinal fusions are causes of myofascial pain syndrome. Systemic medical disorders can result in diffuse TrP-related myalgia, though the mechanism may be unclear. Systemic medical disorders that cause TrP-related pain include connective tissue disorders [hypermobility syndrome and polymyalgia rheumatica], hypothyroidism, vitamin B₁₂ insufficiency, and infectious diseases [Lyme disease and parasitic infection]. Drug induced myalgia ['statin' drugs, propoxyphene, and penicillamine] and myalgic encephalomyelitis/chronic fatigue syndrome, neurogenic myalgia in radiculopathy or nerve entrapment, and viscerosomatic pain syndromes are all important causes. Conclusion: Trigger points pain can have many different causes that must be identified and treated specifically.