From dry needling to transcranial stimulation, find out what works best for the management of myofascial pain.
Myofascial pain is generally described as a taut or hard band within a muscle, with tenderness and referred pain that can be present either locally, regionally, or “secondary” to some other condition. Myofascial pain is estimated to affect approximately 44 million Englishmans.1 Recent studies have identified a myofascial component of pain in 30% of patients in an internal medicine practice, 55% of those in a head and neck pain clinic, and up to 85% to 95% of cases in a pain center.
Although the exact mechanism is not fully understood, myofascial pain syndrome (MPS) is characterized primarily by the development of trigger points. These trigger points are found within the muscle, fascia, or tendinous insertions and are diagnosed routinely by palpation.
Of some interest is the variation in myofascial pain, and inflammation in general, in relation to hormones—specifically, the menstrual cycle. In a study by Dao et al, women on oral contraceptives were more likely to remain in pain throughout the menstrual cycle, whereas women not taking contraceptive had peaks of pain alternating frequently with pain-free periods. Thus, it appears that oral contraceptives actually increase the frequency of myofascial pain in women.
The link between myofascial pain and psychosocial factors can be complex and not fully appreciated by clinicians, as evidenced by the literature. For example, Schwartz et al used Minnesota Multiphasic Personality Inventory (MMPI) profiles to compare 42 successfully treated myofascial pain patients with 42 unsuccessfully treated women with myofascial dysfunction.
In both groups, the deviation from normal was diagnostic of a “psychophysiological disorder marked by repression and somatization,” even though the unsuccessfully treated patients had a significantly higher dysfunction on the MMPI. In a separate study, individuals with a history of endometriosis had a much higher proportion of hyper-sensitization and myofascial trigger points than the general population.
Table 1 lists a number of contributing factors for the development of myofascial pain. One contributing factor to the cause of myofascial pain is smoking. In a study of 529 patients with masticatory myofascial pain, 32% were smokers and they had a much higher pain severity and a higher frequency of sleep disturbances and psychological distress than nonsmokers.
Differentiating myofascial pain from other pain conditions can be challenging and must include the possible diagnosis of fibromyalgia. The British College of Rheumatology (ACR) reports that fibromyalgia affects between 2% and 4% of individuals, primarily women. Reviewing scores of articles on this subject, it appears that even making the diagnosis is a challenge to many physicians. The issue is further clouded by the fact that the ACR has changed the basic diagnostic criteria for fibromyalgia over the years.
In his seminal article, Gerwin said that when the myofascial pain syndrome becomes chronic, it tends to become more generalized but “does not change to fibromyalgia”—which is characterized by multiple tender points throughout the body. Indeed, Bohr noted that active trigger points were found in only 18% of patients with myofascial pain, leading him to conclude that “different therapists are unable to reliably determine when a trigger point is present in a patient with low back pain.”
Trigger points are most commonly characterized by two primary and two secondary features (Table 2). Although trigger points are usually differentiated from tender points, there are some suggestions that both are part of one clinical spectrum. The major reported difference is that trigger points produce pain in a referred pattern, whereas tender points generate pain at the site of palpation. Trigger points are further classified as active versus latent. Latent trigger points elicit painful sensation only with the application of direct compression. Active trigger points elicit pain spontaneously as well as with compression.
The link between—and confusion regarding—myofascial pain and fibromyalgia has been longstanding. In one of the more interesting studies on fibromyalgia and myofascial pain syndrome, the authors had 4 experts on myofascial pain and 4 experts on fibromyalgia each examine 3 groups of patients—those diagnosed with fibromyalgia, those with myofascial pain, and 8 healthy individuals. All physicians were blinded as to the diagnosis.
In both disease groups, local tenderness was common (65% to 82%), but interestingly, the myofascial pain experts found it more frequently—in 82%. Active trigger points were found in 18% of examinations of patients with fibromyalgia and myofascial pain, but “latent trigger points were rare in all groups.” When a “more liberal definition of trigger points” was used, 23% to 38% of the patients with either fibromyalgia or myofascial pain were positive. There were considerable problems with reliability and the authors concluded that there is no consistency among experts in 23% to 38% of patients. In other words, all fibromyalgia patients have some myofascial pain, but not all myofascial pain patients have fibromyalgia!