Factores que promueven la persistencia de mialgia en el síndrome de dolor miofascial y en la fibromialgia / Factors that promote persistent myalgia: myofascial pain and fibromyalgia

Existen múltiples causas de dolor muscular que deben tenerse en cuenta en el diagnóstico diferencial de los síndromes de dolor miofascial (SDM) y del síndrome fibromiálgico (SF). El SDM y el SF no son diagnósticos definitivos en sí mismos, sino que son síndromes con causas. Las causas subyacentes de mialga no tratadas pueden explicar por qué se produjo el dolor muscular y por qué persiste. Las causas pueden ser anormalidades mecánicas como las disfunciones vertebrales y pélvicas, y el estrés ergonómico o postural. Algunas enfermedades médicas sistémicas también causan mialgia. En esta categoría pueden incluirse alteraciones hormonales como el hipotiroidismo, trastornos nutricionales como las deficiencias de hierro o de vitaminas, y las enfermedades infecciosas como la enfermedad de Lyme o infestaciones parasitarias. Patologías del tejido conectivo como el lupus eritematoso pueden ser relevantes. Finalmente, las vísceras presentan un dolor referido muscular que produce SDM característicos. La identificación y el tratamiento de estas afecciones mejoran el resultado terapéutico del SDM y del SF

There are many causes of muscle pain that must be considered in the differential diagnosis of myofascial pain syndromes (MPS) and fibromyalgia syndrome (FMS). MPS and FMS are not final diagnoses in themselves, but are syndromes with causes. Untreated underlying causes of myalgia can explain why muscle pain occurred, and why it persists. Causes include mechanical abnormalities such as pelvic and spinal dysfunction, and ergonomic and postural stresses. Systemic medical illnesses also cause myalgia. Included in this category are hormonal disorders like hypothyroidism, nutritional disorders like iron and vitamin deficiencies, and infectious illnesses like Lyme disease and parasitic infestation. Connective tissue diseases like Lupus are relevant. Finally, visceral organs have a muscular pain referral that produces characteristic MPS. Identification and treatment of these conditions improves the outcome of treatment of MPS and FMS

Classification, epidemiology, and natural history of myofascial pain syndrome.

Myofascial pain syndrome is a disease of muscle that produces local and referred pain. It is characterized by a motor abnormality (a taut or hard band within the muscle) and by sensory abnormalities (tenderness and referred pain). It is classified as a musculoskeletal pain syndrome that can be acute or chronic, regional or generalized. It can be a primary disorder causing local or regional pain syndromes, or a secondary disorder that occurs as a consequence of some other condition. When it becomes chronic, it tends to generalize, but it does not change to fibromyalgia. It is a treatable condition that can respond well to manual and injection techniques, but requires attention to postural, ergonomic, and structural factors, and toxic or metabolic factors that impair muscle function.

Myofascial pain and fibromyalgia: Diagnosis and treatment.

Myofascial pain syndrome (MPS) and fibromyalgia (FM) are common muscular pain syndromes. They are both characterized by tenderness, but MPS is further characterized by the myofascial trigger point that has a taut band and causes referred pain. FM can be either primary (idiopathic) or secondary. MPS is always secondary to some muscle stressor. The diagnosis of these conditions is generally made by physical examination. Algometry can quantify the tenderness. EMG of the trigger point and diagnostic ultrasound can provide objective evidence of the trigger point. Biochemical markers and other phenomena associated with FM have not yet been shown to be either specific or sensitive enough to use as clinical indicators of the condition. Tryptophane is low in the serum and spinal fluid of FM patients, whereas substance P is elevated in the spinal fluid. Treatment of MPS is effective when the trigger point is inactivated and underlying mechanical or medical perpetuating factors are corrected. Treatment of fibromyalgia is more difficult as the drugs commonly used, such as the tricyclic antidepressants, which have uncertain benefits; and exercise, which clearly shows a short-term benefit, fail to provide long-lasting relief at 4 years.

Myofascial pain syndromes in the upper extremity.

Myofascial pain syndromes of the upper extremity are common causes of pain that may follow trauma and are associated with acute or chronic musculoskeletal stress. The syndromes are characterized by the presence of the myofascial trigger point, a physical finding that is reliably identified by palpation. Local and referred pain are hallmarks of the syndrome, and the referred pain patterns may mimic such conditions as radiculopathy and nerve entrapment syndromes. Treatment is directed toward inactivating the myofascial trigger point, correcting underlying perpetuating factors, and restoring the normal relationships between the muscles of the affected functional motor units.

Interrater reliability in myofascial trigger point examination.

The myofascial trigger point (MTrP) is the hallmark physical finding of the myofascial pain syndrome (MPS). The MTrP itself is characterized by distinctive physical features that include a tender point in a taut band of muscle, a local twitch response (LTR) to mechanical stimulation, a pain referral pattern characteristic of trigger points of specific areas in each muscle, and the reproduction of the patient's usual pain. No prior study has demonstrated that these physical features are reproducible among different examiners, thereby establishing the reliability of the physical examination in the diagnosis of the MPS. This paper reports an initial attempt to establish the interrater reliability of the trigger point examination that failed, and a second study by the same examiners that included a training period and that successfully established interrater reliability in the diagnosis of the MTrP. The study also showed that the interrater reliability of different features varies, the LTR being the most difficult, and that the interrater reliability of the identification of MTrP features among different muscles also varies.

Neurobiology of the myofascial trigger point.

The clinical phenomenon of the MTrP is accessible to any clinician who takes the time to learn to palpate skeletal muscle gently and carefully, and who is willing to learn the functional anatomy necessary to understand the regional spread of MTrPs through functional muscle units (Travell and Simons, 1992). Yet despite the years of clinical study of MPS, the pathophysiology of the central feature, the trigger point, has remained elusive. Many investigators have contributed to the general understanding of the mechanisms of pain perception, but we owe a particular debt of gratitude to Dr Seigfried Mense of Heidelberg for his pursuit of the study of pain originating in muscle lesions. However, Dr Mense would be the first to caution us against the direct transference of the results obtained with an inflammatory lesion produced in the experimental animal to the pain of MTrPs in the clinic patient. Notwithstanding that, researchers in the field of pain have given us an understanding of the basis for the hyperalgesia, allodynia and the previously difficult-to-understand finding of referred pain zones that we see daily in our patients. Finally, the interesting initial observations of Hubbard and Berkoff (1993), suggesting that the muscle spindle may be associated with the trigger point, open yet another door in our understanding of the nature of MPS.

Myofascial aspects of low back pain.

Myofascial TrPs are an often overlooked but treatable source of pain and discomfort in the low back. They often complicate or coexist with other causes of low back pain, and they can mimic other neuromuscular or back musculoskeletal problems. Successful treatment of myofascial pain requires the identification of TrPs by manual examination, identification of mechanical or systemic perpetuating factors, treatment of the specific TrPs, and corrective action to prevent their recurrence.