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10 Articles in Volume 12, Issue #6
Carpal Tunnel Syndrome
Case Studies in New Daily Persistent Headache
Hormone Testing and Replacement in Pain Patients Made Simple
Management of Prenatal Low Back Pain
Managing the Diabetic Patient with Dementia
Myofascial Pain Syndrome: Uncovering the Root Causes
New Tools for Improving Patient-to-Physician Communication in Clinical Practice
Suicide and Suffering In the Elderly: We Must Do Better
Three Cases Highlight the Challenges Of Treating Rheumatoid Arthritis
Understanding the Sources of Morphine

Myofascial Pain Syndrome: Uncovering the Root Causes

Multiple contributing factors are linked to the development of myofascial pain syndrome including trauma, postural imbalances, psychological stressors, sleep deprivation, chronic disease states, vitamin insufficiencies, and spinal degenerative conditions.

Case: Myofascial Pain Syndrome

A 31-year-old Web site developer presents to his primary care provider with progressively “annoying” right shoulder and scapular pain that has been present for the past year. He describes his pain as a “tightness,” intermittent, and often occurring at the end of his workday or following exercise. While only a 3 out of 10 on the numerical pain scale, his pain seems to persist once it occurs and limits his ability to play tennis, volleyball, or weight lift at the gym. His pain rarely radiates down his arm and typically remains confined to his neck, trapezoid, and periscapular regions (see photo below). A trial of massage therapy helped temporarily, but the pain seems to return once he resumes his recreational activities.

 

Myofascial pain is an increasingly recognized etiology of non-acute musculoskeletal pain. Although not often considered in the differential diagnosis of musculoskeletal pain until the past 10 to 15 years, myofascial pain is now estimated to affect approximately 44 million Americans.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.2-5 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.6

Trigger Points
Trigger points are most commonly characterized by the following two primary features as well as two secondary features.

Primary features:

  • Palpable taut muscle fibers
  • Consistent localized or referred pain generation by palpation

Secondary features:

  • Restricted range of motion of involved muscle
  • Local twitch response with needle insertion7,8

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.9 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.10 For the purposes of this discussion, MPS will encompass both tender and trigger points.

Clinical Presentation And Pathophysiology
Clinically, myofascial pain often presents as a deep aching sensation, described as an area of “tightness” or “stiffness” by the patient. Myofascial pain is aggravated by use of the affected muscle and frequently responds to mechanical stressors such as stretching, pressure, anxiety, cold, or heat. It is occasionally associated with paresthesias. In many cases, it is preceded by acute or repetitive muscle trauma.

Table: Multiple contributing factors in MyofascialPain

Multiple contributing factors are identified in the development of MPS including trauma, postural imbalances, psychological stressors, sleep deprivation, chronic disease states, vitamin insufficiencies, and spinal degenerative conditions (Table 1).Theoretically, these states of medical or structural aberrance induce motor endplate dysfunction of the affected neuromuscular junctions. Prolonged motor endplate malfunction results in a cascade of myoneural changes including muscle fiber degeneration, regional fibrosis, and formation of the characteristic taut bands of MPS. Likely due to frequent overloading, the trapezius is often the most commonly affected muscle. A review of more recent medical literature suggests that the etiology may be linked to structural conditions such as cervical radiculopathy, muscular trauma such as whiplash, and postural-related stressors. MPS may serve as a “red herring,” distracting health care providers from other underlying issues. We suggest a deeper investigation in the setting of MPS with prior history of trauma or other regional complaints before treating MPS in isolation.

Photo: Patient with mild asymmetry of the right trapezius and levator scapulae muscles

Cervical Radiculopathy
Cervical radiculopathy (CR) is a condition characterized by pain in the neck, shoulder, and usually one or both upper extremities due to compression or irritation of one or more of the cervical spinal nerve roots.11 It can be associated with paresthesias, sensory and/or motor dysfunction, as well as reflex changes typically within the distribution of the affected nerve root.11 The C7 nerve root is the most commonly involved level.11

Although CR typically results from cervical disc herniation (posterolateral is most common) or cervical spondylosis, several recent studies suggest myofascial pain may play a role in its clinical presentation. In one cross-sectional study of 16 subjects diagnosed with unilateral cervical radiculopathy by history and physical exam findings, a greater number of tender points were found on the affected side (75 vs 34, P<0.01) compared to the asymptomatic side.12 A myotomal subgroup analysis of those subjects with C7 radiculopathy demonstrated a significantly higher number of trigger points among those muscles innervated by C7 on the affected (23 vs 7, P<0.02).12

A larger study evaluated 244 patients diagnosed with CR by both clinical presentation as well as concordant magnetic resonance imaging (MRI) findings to compare the prevalence of latent and active trigger points to those of asymptomatic controls.13 Data analysis revealed that active trigger points were found only in those patients with CR. Interestingly, there was no difference in the number of latent trigger points between groups. Additionally, the number of active myofascial trigger points was significantly greater in those patients with a medial disc herniation compared to a posterolateral herniation (P=0.041). The results of this study demonstrate an association between myofascial pain and CR.13 Other studies (mostly retrospective in nature) have more closely delineated this association by correlating a cluster of trigger points within a specific muscle group with lesions of its corresponding nerve root.14 Some research has even shown a higher pain intensity level of those trigger points found in patients with cervical disc lesions compared to those of patients without cervical pathology.14

Whiplash Injury
Another emerging etiology of myofascial pain is whiplash injury. Whiplash constitutes a forced trauma to the cervical spine,15 whereby the neck is forced into rapid extension followed by flexion.16 This mechanism of injury most commonly results from rear-end motor vehicle crashes.16 Although pain, neck stiffness, and reduced neck mobility typically occur acutely,15 whiplash associated disorder (WAD) is diagnosed when these symptoms persist beyond 1 year and are accompanied by non-resolving weakness or other neurological deficits.17-20 While a majority (≈90%) of whiplash associated pain subsides,17,19,21-23 symptoms will persist in a small proportion of patients as chronic WAD.17 Although the mechanism by which whiplash associated symptoms resolve in some patients and persist in others is still not entirely clear, a few studies have identified several features characteristic to both conditions.

Table: Practical applications to improve clinical outcomes

Several studies have shown that an overwhelming majority of whiplash victims—even from low-velocity collisions—tend to suffer from some type of skeletal or muscle pain. More recent studies suggest that these symptoms may involve a myofascial component. One observational study of 157 subjects with whiplash associated injuries, who reported pain and showed objective findings of weakness or sensory deficit, assessed the degree of muscle tenderness and mechanosensitivity at 12 days, 3 months, and 1 year from the day of injury. The study revealed non-recovered patients had an increased number of tender point scores at 12 days (P<0.05), 3 months (P<0.05), and 1 year (P<0.05) compared to those who recovered. Non-recovered subjects also experienced tenderness at lower measured pressure thresholds compared to those subjects whose whiplash symptoms resolved. Finally, over the course of 1 year, additional trigger points appeared distally from the initial site of injury, suggesting a dynamic component to these patients’ pain syndromes.15

A cross-sectional study of 124 subjects compared the prevalence of trigger points among patients with one of the following four conditions: WAD, fibromyalgia, non-traumatic cervical syndrome, or primary depression. A group of age-matched controls were also included (n=24). The results demonstrated a statistically significant greater number of trigger points among both the WAD as well as the fibromyalgia cohorts (P<0.05).24 Among the groups, the WAD cohort exhibited a proportionately greater distribution of trigger points within the semispinalis capitis muscles, scalenes, and sternocleidomastoid muscles compared to the relatively smaller increased distribution of trigger points among the trapezius and levator scapulae in the fibromyalgia cohort. The muscles demonstrating greater myofascial trigger points in the whiplash group correspond with those muscle groups typically involved during a whiplash event.24

Postural Habits
Postural abnormalities have also been implicated in the development of myofascial pain. These include both genetic anatomical variants such as leg length discrepancy, small hemi-pelvis, and abnormally shortened upper arms, as well as postural imbalances described below. In contrast to dynamic muscle groups that facilitate body movement, stabilizing core muscles suspend the skeletal elements in a specific posture for a prolonged period. It is theorized that poor body posture can prolong a state of contracture in stabilizing muscles, resulting in similar neuromuscular degradative changes as noted earlier. With the rise of musculoskeletal complaints in those patients performing low-level static exertions (LLSEs) such as keyboard and mouse use, several recent studies demonstrate a relationship between postural imbalance and myofascial pain.25-27

In 1999, David Simons and Janet Travel first identified postural habits as potential contributors of myofascial pain in their landmark publication, Myofascial Pain and Dysfunction: The Trigger Point Manual.28 Subsequent studies over the past decade confirmed this association. Case reports by physiotherapists with expertise in myofascial pain found that treatment of myofascial trigger points (MTrPs) and the correction of common maladaptive postural positions such as leg crossing, side leaning, and elbow folding resulted in resolution of the initial pain complaints.25 As MPS evolved as a diagnostic consideration in clinical research, its prevalence among musculoskeletal complaints began to increase. A study of subjects who regularly performed LLSEs found that trapezoidal MTrPs developed after just one hour of continuous typing.26 In another case series of 56 patients with new onset of upper extremity/cervical pain engaged in intense keyboard and/or mouse use (>3 hours per day), myofascial pain was overwhelmingly the most common diagnosis, occurring in 88% of patients with shoulder complaints and in 80% of those with forearm pain. Treatment of MTrPs and ergonomic correction of postural imbalances resulted in symptomatic improvement in nearly all cases.27

Conclusion
Certainly, MPS is a condition that is prevalent in the general population and warrants consideration in the differential diagnosis of musculoskeletal pain. Although often deemed localized to muscle itself, the diagnosis requires an investigation into potential underlying causes. In many cases, a structural, medical, or traumatic comorbidity also exists. Attention to the underlying factors may ensure more timely effective management and improved patient outcomes (Table 2).

Last updated on: May 6, 2019
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