However, given that they have been part of the landscape for twenty years, it is unlikely they will be forgotten and many physicians will still consider them part of the picture for fibromyalgia syndrome (FMS).
The short report on the 1990 ACR criteria provides a listing of the tender points and their location. Here is a little bit more information on tender points.
Most patients with FMS have tender point pain thresholds that are about half the 1990 ACR criteria of 4 kilograms, which is about 2 kilograms, or 4 pounds of pressure. Tender point counts are also not uniformly distributed within different groups of FMS patients, for example, age groups. In fact, most people are more likely to have 16 or more rather than 11 to 15 out of a possible 18.
Tender point counts are only slightly or moderately correlated to clinical pain intensity. Most studies suggest that tender points neither predict the extent of widespread pain nor do they correlate with clinical pain intensity ratings. As treatment for FMS progresses, tender points appear to be the most resistant relative to symptom resolution. For example, a study that looked at a number of different studies all dealing with the usefulness of antidepressants in FMS found that even with improvements in clinical pain and functional status tender point tenderness, while showing modest improvement, seemed to be a persistent characteristic.
Another source of pain is the actual muscle tissue in which the tender point lives. Looking at samples of muscle tissue, termed muscle biopsies, from patients with FMS, researchers found changes called ragged-red fibers, inflammatory infiltrates, and “moth-eaten” fibers. In other words, the muscle tissue of patients FMS was different than people who did not have FMS.
Other researchers have used more elaborate tools, one of which is called nuclear magnetic resonance (NMR) spectroscopy. With a phosphorus atom that has been “labeled” to have a certain “electron signal,” called 31P, different groups of researchers were able to study how the muscles of patients with FMS are able to use energy. Phosphorus is an atom that is attached to molecules that are very important in the energy processing reactions of cells so being able to measure just what happens to this atom can provide clues as to how efficient a certain tissue type may be when it comes to using energy.
The studies have shown that the symptoms of pain and fatigue experienced by patients can be correlated to metabolic changes in the muscle tissue of patients with FMS. Most of the findings seem to be pointing in the same direction – the muscles of patients with FMS are simply less efficient. Inside cells are organelles called mitochondria, which are nicknamed the “power-houses” of the cells. It is inside these organelles that the actual energy reactions take place, generating a molecule called ATP or adenosine triphosphate. ATP is best thought of as the energy currency of the cell. It is used to power almost all of the cell’s reactions to make proteins, DNA, and nearly anything else the cell has to do to “make a living.”
Given its name, you can ascertain that adenosine has three phosphate atoms, so by labeling the phosphate atoms, researchers can keep tabs on just where the ATP is going and what it is doing. That is how they were able to figure out that the muscle cells of patients with FMS were just not operating at maximal efficiency. What is interesting is that the “ragged-red” fibers the scientists saw when they were looking at FMS muscle tissue under the microscope is what you would see when you have “sick” mitochondria. So, the fancy NMR studies match what is seen with a simple microscope.
If muscles don’t get enough blood, a condition termed, ischemia, this can also generate pain. Patients with FMS will complain of a sensation of “muscle swollenness” during exercise. Another fancy device called, contrast enhanced colour doppler imaging was used to study muscular blood flow. This demonstrated that was a dampened increase in muscular vascularity, or blood flow, both after active and during passive work even at limited levels comparable to those of activities of daily living. This could be explained by simple deconditioning, in other words, people just aren’t that fit. Another explanation is that the nervous system isn’t appropriately responding by allowing the blood vessels to open up and let in more blood when they are being used.
Although FMS patient may not be that physically fit this argument quickly gets into a chicken and egg situation. Are people with FMS not fit and this contributes to their disease or does their disease make it even more difficult for people to exercise and become more fit? In support of the latter explanation, it seems the nervous system of people with FMS does not respond the way it should and allow the blood vessels in muscles to open up, allowing more blood to flow through the exercising tissue.
Now what happens? Muscle ischemia is one factor leading to local hypoxia, or decreased oxygen. Hypoxia accelerates the creation of a specific compound with a very elaborate name –advanced glycation end products (AGEs). These products are able to do things which are not very nice. In short, they end up creating an environment which is what researchers call an “inflammatory state,” which means quite like it sounds. The area around the cell looks like it has been injured, which, quite literally, it has, by virtue of the AGEs. When this happens, the body sends in the cells it normally would to fight an infection – macrophages, fibroblasts, and other cells whose job is to “conquer and destroy.” In other words, they destroy any damaged tissue and replace it with other tissue.
This is well and good normally; however, in this case, the injury was created by a “malfunction” created by the inability of the nervous system to allow the appropriate amount of oxygen to reach muscles. It should not have happened and if it keeps happening more “inflammatory states” are going to be created. The problem is that the tissue that is used to replace the damaged tissue is just not quite as good as the original tissue when it was functioning well. It’s similar to keep having your car repaired after an accident. If you keep on having accident after accident, pretty soon your car isn’t going to be worth much.
A bigger problem occurs when the AGEs start changing proteins that live a long time, like the protein called collagen. When this happens, there is always a signal being sent out to send in the “conquer and destroy” cells because the collagen isn’t able to be easily replaced and the AGEs keep hanging around. To make matters worse, patients with FMS seem to have a problem with collagen to begin with. Researchers have found abnormal collagen wrapped around the nerve fibers in the deep connective tissue of skin in patients with FMS. This collagen is denser than normal. Now, there is a positive feedback system. The abnormal collagen gets modified by the AGEs which creates an inflammatory response that further decreases the ability of the area to get oxygen which creates more AGEs which makes the inflammatory response worse, creating more AGEs, and so on. As a result, since hypoxia amplifies the pain response, the pain sensed by FMS patients worsens. I imagine you get the picture of what is going on.
Although tender points have been the center of attention, it is also important to remember that patients with FMS also have trigger points. Trigger points were traditionally thought to be present in patients who suffer from a condition called myofascial pain syndrome. Many times you can feel them yourself. They are the “knots” within muscles; most people feel them in their shoulders muscles along the tops of their backs. Trigger points were categorized into two types – active and latent. Both active and latent trigger points are areas of tenderness or “knots” on a taut muscle band. If you have had them treated by a physician the doctor may have put a needle into them, injecting an anesthetic solution or a solution of sterile water or saline (a sterile, slightly salty solution). Acupuncturists may also have treated them in the same way. Often when this happens the muscle twitches and you can even feel a tingling sensation, sometimes even pain, shoot up to different parts of your body. This is called “referred pain,” and is actually one of the distinguishing characteristics of trigger points.
Dr. David Simons and Dr. Janet Travell, who later became the White House physician for John F. Kennedy published two very thick books just on trigger points. They mapped all of the trigger points in the body with very specific instructions on how to find them and just where each of the trigger points would send their patterns of referred pain. This is one of the unusual characteristics of trigger points. Regardless of the person, each trigger point sent pain to pretty much the same location. A major differentiating characteristic between active and latent trigger points is that the latter are not spontaneously painful.
Trigger points had been previously noted in patients with FMS as early as 1986. One published study found more than 50% of FMS patients with greater than ten active trigger points. Trigger points are found in muscles. If you have read the short report on the 1990 American College of Rheumatology’s FMS Criteria you may have noticed that three of the 1990 ACR three tender points (not trigger points) are described over non-muscular locations – the cervical, second rib, and knee. However, these actually correspond to muscle trigger points that are located in the lower part of the sternocleidomastoid muscle, the outside portion of the pectoralis muscle, and the lower vastus medialis muscle, respectively. (Now you know some anatomy to impress your physician)
The first electrophysiologic evidence that the 18 tender point sites in FMS are either latent or active muscle trigger point sites was published in 2009. The first study to quantitatively map active and latent trigger points in FMS was also published that year and did so with 13 locations in the trapezius muscle. Just think - the ACR had two tender points in the trapezius muscle, but these researchers mapped over 13 trigger points in the same muscle!
There were some other interesting findings. The FMS study patients showed active trigger points in locations that corresponded to latent trigger points in healthy people, and the FMS patients were significantly more tender at all locations, especially at anterior and mid portions of the muscle. Finally, the local and referred pain that could be brought about by manual pressing of the trigger points did a very nice job of reproducing the neck and shoulder pain patterns reported by the FMS patients.
The total number of active trigger points has been shown to be positively correlated with the intensity of spontaneously reported pain in FMS patients – the more trigger points, the more intense the pain FMS patients feel. The leading researcher in this field, Dr. Hong-You Ge, feels that that nearly all major muscles in FMS patient contain active trigger points and the widespread spontaneous pain patterns seen in these patients result from an “adding up” or a summation of all the regional pains from active trigger points. Dr. Ge also published the first study in 2010 that showed more than 90% of the ACR tender point sites are also trigger points and can reproduce the pain patterns described by FMS patients in their neck and shoulders, arms, thighs and gluteal regions. He confirmed this using an instrument called an electromylograph that uses a tiny needle which, when inserted directly into the tiny trigger point, registers unique electrical activity only made by active trigger points.
Even given their moniker, latent trigger points are not benign. Mechanical stimulation of a latent trigger point, either manually or with a needle, can produce referred pain, just not of the same character as that of an active trigger point. In general, although latent trigger points are not spontaneously painful they can become active under demanding conditions such as intense physical activities, stress, and disturbed sleep. Latent trigger points have also been found to induce muscle cramps when they become stimulated, which can cause even more discomfort.
Trigger points are not easy to identify and many physicians do not know how to accurately find them; some physicians simply do not want to take the time to do so. Finding them is an acquired skill which is one of the reasons an experienced pain physician is important in treating FMS.
They can be treated in several ways. One method is to inject into them a solution of a local anesthetic, such as lidocaine. Another approach is to apply a prescription patch that has a lidocaine solution “built-in” to the patch. This allows a constant amount of anesthetic to be absorbed into the tissue immediately below the patch. If the trigger points are not too deep the patch can be an effective treatment. However, if the trigger points are deep within the tissue the anesthetic will not be able to reach them. Both approaches “shut down” the mechanisms keeping the trigger point “active” and the tissue relaxes. Following up with physical therapy that includes a stretching program or sessions using ultrasound following a written prescription from a physician is also an important component for providing long term resolution.
Acupuncture is another treatment method, especially a type of acupuncture that uses electrical stimulation between certain specific acupuncture points. This type of acupuncture treatment, as the case for most acupuncture treatments, is to free up blocked energy, which is termed, “Qi” in Chinese Medicine. The role of acupuncture in FMS will be the topic of a short report that you will see on this web site in the future.
The role of trigger points and the pain input from muscle tissues in the creation and maintenance of the pain of FMS syndrome, through a process called central sensitization, and the role of decreased pain inhibitory mechanisms is an area of increasing research and will be discussed in short reports to come. So, you haven’t heard the last of trigger points; they may be gone from the 2010 ACR Criteria, but they are certainly not forgotten.
