Alternative Health Information

Trigger points

Trigger points are hyperirritable spots in skeletal muscle that are associated with palpable nodules in taut bands of muscle fibers. The palpable nodules are the result of small contraction knots in muscle tissue. They are an extremely common cause of pain and are frequently misdiagnosed as some other problem, which often leads to a great deal of anguish for the patient.
A trigger point does not really cause a contraction, it causes a contracture. A contraction is muscular activity mediated by the nervous system, while a contracture is a mechanical "sticking" of the muscle fibers with no involvement from the nervous system. Usually an event of muscular overload causes a prolonged release of Ca++ ion from the sarcoplasmic reticulum (storage unit for the muscle cell) which results in a sticking of the untrained or overloaded cells. This leads to a compression of capillaries and results in an increased local energy demand and local ischemia (loss of blood circulation) to the area. This "energy crisis" (as it is termed in the seminal work on trigger points) causes the release of chemicals that augment pain activity. Since an involved muscle is weakened by this sustained shortening, surrounding muscles can be made to pick up the slack and develop trigger points themselves.
Trigger points are extremely painful on compresson and often elicit referred pain, tenderness and motor dysfunction in predictable patterns.
Trigger points have been a subject of study by a small number of doctors for several decades although this has not become part of mainstream medicine. The existence of tender areas and zones of induration in muscles has been recognized in medicine for many years and was described as muscular rheumatism or fibrositis in English; German terms included myogelose and myalgie. However, there was little agreement about what they meant. Important work was carried out by J.H.Kellgren at University College Hospital, London, in the 1930s and, independently, by Michael Gutstein in Berlin and Michael Kelly in Australia (the latter two workers continued to publish into the 1950s and 1960s). Kellgren conducted experiments in which he injected saline into healthy volunteers and showed that this gave rise to zones of referred pain lower down the limbs.
It was however an American physician, Janet Travell, who was responsible for the most detailed and important work. She published more than 40 papers between 1942 and 1990 and in 1983 the first volume of The Trigger Point Manual appeared; this was followed by the second volume in 1992. A second edition of this work has now been published. In her later years Travell collaborated extensively with her colleague David Simons. A third edition is soon to be published by Simons and his wife, both of whom have survived Travell.
In spite of all this work, the trigger point concept is unknown to most doctors, who still learn little or nothing about the subject at medical school. Other health professionals, such as physiotherapists, osteopaths, and chiropractors are generally more aware of these ideas and many of them make use of trigger points in their clinical work. According to Travell and Simon's seminal work on the subject, Myofascial Pain and Dysfunction: The Trigger Point Manual, around 75% of pain clinic patients had a trigger point as the sole source of their pain. In addition, the following conditions are often diagnosed (incorrectly) when trigger points are the true cause of pain: carpal tunnel syndrome, bursitis, tendinitis, angina pectoris, sciatic symptoms, along with many other pain problems. Arthritis is often cited as the cause for pain even though pain is not always concomitant with arthritis. The real culprit is a trigger point, normally activated by a certain activity involving the muscles used in the motion, by chronically bad posture, structural deficiencies such as a lower limb length inequality or a small hemipelvis, or nutritional deficiencies.
The main innovation of Travell's work was the introduction of the myofascial pain syndrome concept. This is described as a focal hyperritability in muscle that can strongly modulate central nervous system functions. It needs to be distinguished from fibromyalgia, which is characterized by widespread pain and tenderness and is described as a central augmentation of nociception giving rise to deep tissue tenderness that includes muscles. It is considerably more difficult to treat.
Trigger points can be classified as latent or active, depending on whether they are giving rise to symptoms. Latent trigger points can cause muscle shortening and weakening but not spontaneous pain. The causes of activation include acute or chronic muscle overload, indirect activation by other trigger points, visceral or joint disease, emotion, and radiculopathy. The radiation effects include pain and also other sensations; the affected muscles may also be weak.
Diagnosis of trigger points is mainly by manual palpation. There are changes in the "feel" of the tissues and the patient will report local tenderness, sometimes with radiation effects. There may be a twitch in the affected muscle.
Treatment of trigger points may be by local compression, injection of a local anesthetic such as procaine hydrocloride (novocain), or "spray-and-stretch" using a cooling (vapocoolant) spray. Practitioners of medical acupuncture often use trigger points as the basis for their treatment and studies have shown a considerable similarity between the locations of trigger points and classic acupuncture points


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