RECOMENDACIÓN

(Travell & Simons, 1983; 1992)

Trigger points may be found in muscles, tendons, ligaments, and joint capsules. They are classified as either latent or active. Latent trigger points can be found in normal people, in whom they give rise to no symptoms. For example, the midpoint of the trapezius muscle is a latent trigger point, and so is the infraglenoid tubercle, on the scapula below the glenoid cavity just above the origin of the long head of the triceps. Firm pressure on these and similar sites is painful in almost everyone. An active trigger point is one from which pain is felt spontaneously, either locally or at some distance from it, in the zone of referred pain. Some active trigger points develop from pre-existing latent triggers, but others arise at sites that were not previously tender at all.

In spite of a fair amount of research and quite a lot of speculation, there is no general agreement about what trigger points are. Those that are in muscles possess increased electrical activity, which can be demonstrated if an insulated needle with just the tip exposed is inserted into them, but they show no definite or constant histological features (A. Ward, personal communication). It is possible that they are maintained centrally, by activity originating from the spinal cord. A noxious stimulus could cause reflex maintenance of nociceptor activity in the periphery via an outflow through the sympathetic system; another suggestion is that the trauma may cause reflex maintenance of muscle spasm via motoneurons.

Once they have arisen or become active, trigger points may persist and cause symptoms for long periods: weeks, months, or even years. On the

Needle inserted into trigger point

Skin

Subcutaneous tissue Trigger point

Muscle

other hand, they can often also be abolished, at least temporarily, by simple pressure as well as by the insertion of a needle or in other ways. Lack of awareness about the length of time a trigger point may remain active after an injury has often led doctors to suspect a psychosomatic disorder or even malingering in patients with persistent pain, yet often a complete and permanent cure can be achieved in such cases by the insertion of a simple acupuncture needle.

Trigger points can become active in a number of ways. Trauma, sudden strain, or excessive use of the muscle may do this; so, too, may continued overuse or prolonged contraction, as may occur in people who are psychologically tense. Emotional factors are certainly concerned in their genesis and maintenance. Other causes include prolonged immobilization and infections; and sometimes the cause is unknown.

Travell and Simons distinguish between primary and satellite trigger points; the satellites develop in areas of referred pain. For example, patients with sciatica may have a primary trigger point in the gluteal region and a number of satellite trigger points in the limb below. The term ‘secondary trigger point’ refers to trigger points that may develop in antagonist or synergist muscles.

Muscle with taut bands and trigger points (plan view)

The ATA concept in practice 73

An important feature of trigger points is that they may be associated with taut bands in the muscles. These are thought to be zones of increased contractility. Like trigger points, they may come and go with surprising rapidity.

Examining patients for trigger points

The art of examining patients for trigger points requires practice to learn. It is not taught to medical students so doctors coming to acupuncture have to acquire it. There are two basic techniques. For flat muscles, such as the gluteal muscles, the skin and subcutaneous tissues are moved transversely across the line of the muscle fibres. Travell and Simons describe the action as like that of feeling corduroy. A way of simulating it to some extent is to lay a few pencils side by side on a table, cover them with a cloth, and then move the cloth with the finger across the pencils so that they roll beneath it. The middle finger seems to be more sensitive than the index finger for the purpose, and I find that my left hand is more sensitive than my right, but this may be an individual peculiarity.

The alternative technique of examination, which is required for strap muscles such as the sternomastoid and also for areas such as the anterior and posterior axillary folds, is to use a pincer action, gripping the muscle between thumb and middle finger and drawing the skin and subcutaneous tissues across the underlying muscle as if trying to pull them off it.

It is important to have the muscles under slight tension, though not too much, when searching for trigger points. A totally relaxed muscle cannot be examined in this way, nor can a firmly contracted one.

No instruments are required for detecting trigger points; you need only your fingers. It takes time, however, to build up an awareness of how

much pressure to apply. We start with fairly gentle pressure, both to avoid causing unnecessary pain and because, in some patients, this is more effective; we then apply progressively firmer pressure in an attempt to elicit tenderness. In certain situations, such as the gluteal muscles, considerable pressure may need to be exerted, because the affected muscles, such as the piriformis, lie at depth below other layers of muscle. In all this process of examination we need to keep the anatomy in mind and constantly try to maintain a three-dimensional mental image of what we are feeling.

Some degree of tenderness is normal in muscles if they are pressed sufficiently firmly. The acupuncturist therefore needs to form a mental, or rather a kinaesthetic, image of how much tenderness is to be expected for a particular degree of pressure at a given site. This varies according to the type of patient. In general, women have more latent trigger points than men, so a degree of tenderness in the trapezius muscle that would be accepted as normal in a woman might be abnormal in a man. But it’s not only the absolute degree of tenderness that we need to be aware of; we also compare the two sides of the body, and differences here are particularly significant.

With practice, different degrees of tension can be felt in the muscles, and the above-mentioned strands of taut muscle can be identified; one particularly tender area in each of these strands will be found and this is the trigger point. Sometimes a strand of muscle will twitch under the finger as it slides across the tense strand; this indicates the site of the trigger point. A twitch of this kind can be elicited in most people in that portion of extensor digitorum that controls the middle finger. Another indication is the so-called ‘jump sign’; ‘flinch sign’ might be more accurate because the patient pulls sharply away as the trigger point is encountered. And, of course, patients will generally tell you that they experience pain as the trigger point is pressed.

The locations of trigger points in the various muscles are described in textbooks. As a general rule, referral of pain is from axis to periphery and from proximal to distal, so this gives an idea of where one should be looking for trigger points. However, every patient is different and there is no substitute for careful clinical examination without preconceptions. Restriction of individual movements also gives clues; for example, if a patient has restricted neck rotation this would suggest the presence of trigger points in the opposite sternomastoid since this muscle is responsible for rotation (although other muscles in the neck could of course be affected as well).

Fibromyalgia versus myofascial pain

Up to this point we have been looking at trigger points in the context of what Travell and Simons call the myofascial pain syndrome. That is, we have been talking about fairly localized tender areas and radiation of pain

The ATA concept in practice 75

therefrom. However, there are patients who have some of the features of myofascial pain but who seem to suffer from a different disorder, which is nowadays often labelled fibromyalgia. The main differences are as follows.

䊉 Fibromyalgia affects women much more than men.

䊉 Pain is widespread in fibromyalgia, whereas in myofascial pain it is usually localized although more than one area of the body may affected.

䊉 Patients with fibromyalgia often wake up feeling tired. Sleep may also be disturbed in myofascial pain because of the pain, but sleep disturbance is not part of the syndrome as such.

䊉 Patients with fibromyalgia often have morning stiffness and fatigue. 䊉 Antidepressants may help patients with fibromyalgia, although this is

not necessarily because they are depressed. (However, emotional upsets and stress do seem to be related to the onset of fibromyalgia.) Antidepressants don’t help myofascial pain. Neither fibromyalgia nor myofascial pain respond to non-steroidal anti-inflammatory drugs (NSAIDs).

䊉 Fibromyalgia appears to be part of a spectrum of related disorders, including irritable bowel syndrome, tension headaches, and primary dysmenorrhoea. This is not true of myofascial pain.

䊉 The prognosis of the two disorders differs. Myofascial pain generally responds well to acupuncture whereas fibromyalgia does not; at best, acupuncture seems to give partial relief for a short time in fibromyalgia, perhaps for two or three weeks. This can present the acupuncturist with a difficult problem in the case of patients who find even this brief remission worth while, since the disorder can last for many months or even years; in fact, indefinitely.