Myofascial Pain Syndrome

Although myofascial pain syndrome is a well recognized clinical condition known to be the cause of muscular pain especially neck pain, back pain and headaches, there remains a lot that is not known regarding the pathophysiology, mechanisms of pain referral, and treatment of choice for myofascial trigger points. In addition, myofascial trigger points remain a commonly overlooked cause of chronic neuromusculoskeletal pain and dysfunction.

Medical researchers Drs Travell and Simons define a myofascial trigger point as a tender nodule in a palpable taut band of skeletal muscle. Trigger Points (TrP) are able to generate either local or referred pain, either spontaneously (active) or on digital compression (latent). TrP may become activated by a variety of factors such as poor posture, overuse, biomechanical faults or muscle imbalance. TrP exhibit a local twitch response (muscle fasciculation) or jump sign (flexion withdrawl response) in response to digital pressure or dry needling. See explanatory chart.

Physiology of Myofascial Trigger Points

Understanding the biochemistry of active myofascial trigger points and determining the local biochemical effects of needle insertion may help us understand the mechanisms behind the initiation and amplification of myofascial pain and how dry needling works. Each TrP contains a sensory component, a motor component, and an autonomic component. Thus TrP pain syndrome involves local myofascial tissues, the central nervous system (CNS), and systemic biomechanical factors.

We owe a lot of gratitude to the physician John Kellgren, who during the 1930s made the significant contributions to our knowledge concerning the pathophysiology, diagnosis and treatment of myofascial trigger point pain. Lewis and Kellgren carried out experiments where they injected hypertonic saline into muscles and observed pain being experienced at the injection site and at some distance away, at what they called the zone of pain referral. (Kellgren JH; 1938)
After further investigations into the observed phenomena Kellgren went onto say:

A number of cases of "fibrositis" or "myalgia" have been investigated. The distribution of pain from normal muscles guided me to the muscles from which spontaneous pain may have arisen. Such muscles always presented tender spots on palpation and pressure on these spots reproduced the patient‟s pain.‟

He then went on to confirm that the pain arose as a result of nerve hyperactivity at these tender points by showing that it could be alleviated, by injecting a local anesthetic into the tissues at these tender sites.

Travell’s study of the subject (in the 1940's) led her to conclude that pain that had previously been called rheumatism, fibrositis, myalgia etc arises not only from skeletal muscle itself but also from its fibrous connective tissue. She therefore called the disorder the myofascial trigger point pain syndrome.

(See more detailed information)

Aggravating and Precipitating factors responsible for the development of Trigger Point activity are:

 

Trauma
This may be either a direct injury to the muscle or by the sudden or repeated overloading of it. Alternatively, it may develop when the muscle is subjected to repeated episodes of microtrauma such as occurs with a repetitive strain injury. Commonly back pain, wrist and arm pain.

 

Anxiety
TrP activity may also be brought about when a patient of an anxious temperament holds a group of muscles in a persistently contracted state. Commonly neck pain or headache.

 

Muscle wasting
TrP activity is liable to develop when muscles have become weakened and wasted by malignant disease or a neurological disorder. With respect to strokes, TrP nociceptive pain is liable to develop when weakened muscles become overloaded during attempts to restore movements to them during the recovery stage.

 

Muscle ischemia
TrP activity may arise when, because of arterial obstruction, the muscles of a limb become ischemic.

 

Visceral pain referral
Pain arising as a result of visceral disease is frequently referred to both skin and muscles. When this happens TrPs in muscles situated in this zone of pain referral are liable to become active, with the production of superimposed TrP pain. Commonly neck pain, back pain, shoulder or chest pain.

 

Radiculopathic compression of motor nerves
When pain occurs as a result of spinal nerve root compression, such as from spondylosis or disc prolapse, pain may also arise as a result of the secondary development of TrP activity in the paraspinal muscles. Commonly back pain or sciatica.

 

Climatic causes
TrPs are liable to become active when the muscles containing them are exposed to adverse environmental conditions such as damp, draughts, excessive cold or extreme heat. Commonly back pain, knee pain, neck pain.

Diagnosis of Myofascial Trigger Point Pain Syndrome

Patient history
In order to diagnose a patient as suffering from myofascial pain it is necessary to conduct a complete medical history covering topics such as symptom onset, duration, location, and character of pain, physical/functional impairment, factors that exacerbate or relieve, associated features or secondary signs/symptoms, neurologic history and a psychosocial history. (Ref: Causes of Persistent Myalgia. Gerwin RD; 2005)

 

Pain
This is by far the most common presenting complaint. Typically the pain is described as deep, aching and poorly localized. It is usually restricted to one quadrant of the body, although complex patterns from multiple TrPs may give a wider distribution. It is important to determine the precise nature and pattern of the pain, as would be done when taking a standard medical history. Various pain scales may be employed to standardize the process of determine the patient pain intensity.

Paraesthesia is not uncommon in association with the pain and often confirms in the patient’s mind the false impression that they have a ‘trapped nerve’. Symptoms are generally exacerbated by activity; however, some light exercise involving gentle stretching of the affected muscle may relieve the aching. Frequently, sciatica associated with a back pain is misdiagnosed as a disc protrusion, and is commonly a piriformis muscle TrP.
Some patients will find a tender point in muscle, particularly if the TrP is in an accessible site; and a few will describe some sort of technique they have developed to relieve the pain, which usually involves the application of pressure to the TrP.

Dysfunction.
TrP activity may lead to the development of various autonomic changes. These include lacrimation, regional pilomotor activity and excessive coldness of an extremity. TrPs appear to affect proprioceptive function. In the cervical musculature, in particular sternomastoid, this may be responsible for disequilibrium, even to the extent that the patient may describe true vertigo. In the limb musculature this may result in distorted weight perception. Motor dysfunction includes restricted range, weakness, reduced co-ordination and spasm in other muscles.

Sleep
Myofascial pain may disturb sleep but, more importantly, sleep position often aggravates TrP activity by allowing affected muscles to shorten.

Age
TrPs occur in all age groups but present most commonly in the middle years. The muscles of young active people are probably more resistant to injury, and faster to repair, so less likely to develop or sustain active TrPs. By comparison, the musculoskeletal system of the middle-aged adult is becoming increasingly degenerate, less resilient and slower to heal. In general the middle-aged are less active, but engage in unaccustomed bouts of physical activity. They tend to suffer most with the pain of activeTrPs. Latent MTrPs can be found in the majority of elderly people, causing stiffness and reduced active range of movement, but this age group present less frequently with the pain of active TrPs.

Sex
Women seem to present more frequently with myofascial pain than men. It has not been established whether myofascial pain is more common in women, or whether they are more likely to present with this type of pain. It is certainly true that phenotypic differences can influence biomechanical loading and, for the same mass, women tend to have wider hips and narrower shoulders than men. Biological factors such as these may be important, but socio-economic differences in terms of working environments may also have an influence. For example, a higher proportion of the male workforce performs physically strenuous jobs and it has been noted that these individuals suffer less from myofascial pain than sedentary workers.

Article by Peter Pedersen