Myofascial Pain Syndromes a short review

Simon Strauss M.D.
e-mail: simons@atnet.net.au

Introduction

"Myofascial Trigger Points are among the most common, yet poorly recognized and inadequately managed, causes of musculoskeletal pain seen in medical practice." Ex White House Physician Janet Travell 1976.

Over the last two decades Janet Travell's call for improved recognition and treatment of Myofascial Trigger Points has begun to be answered. Relatively rapid changes in our knowledge have begun to accrue particularly since the establishment of a standardized nomenclature and the usage of pain diagnostic tools.

These advances have led to a major exploration of the epidemiology, pathogenesis of and therapeutic options for pain states caused by muscular Trigger Points, which are now specifically known as Myofascial Pain Syndromes.

The delineation of Chronic Benign Intractable Pain Syndromes of the Neck and Back as being Myofascial Pain Syndromes is of particular importance as these Chronic Benign Intractable Pain syndromes constitute a large proportion of the chronic pain population. Who, because the diagnosis Chronic Benign Intractable Pain Syndromes carried considerable psychological overtones, were frequently exposed to psychologically based therapies, which usually had little effect on pain reduction. Thus the finding that these patient's have a physical cause for their pain is of great significance as it allows for treatments that target the tissue and reflexes that cause and maintain their pain state.

Definitions.

Myofascial Pain Syndromes can be thought of as pain syndromes that are caused by and are maintained by one or more active Trigger Points and their associated reflexes.

Myofascial Trigger Points (MTrPs): May be active or latent.

An active Myofascial Trigger Point is a focus of hyperirritability in a muscle or its fascia that causes pain and tenderness at rest or with motion that stretches or loads the muscle. It prevents full lengthening of the muscle, as well as causing fatigue and decreased strength. Pressure on an active MTrP induces / reproduces some of the patient's pain complaint and is recognised by the patient as being some or all of his or her pain.

A latent Myofascial Trigger Point: does not cause pain during normal activities. It is locally tender, but causes pain only when palpated. It also refers pain on pressure. It can be associated with a weakened shortened more easily fatigued muscle.

Prevalence

The prevalence of Myofascial Pain Syndromes in both non-patient and patient groups has now been extensively documented.

The studies listed below represent a small part of this exploration that has been published in the peer-reviewed literature.

Unselected and Control Groups

A Danish study of 1504 randomly selected people, aged 30 - 60, found that 37% of males and 65% of females had localised myofascial pain.

An American study of 100 male and 100 female airforce personnel (Av. Age 19) determined that 45% of males and 54% females had focal neck muscle tenderness (latent trigger points).

269 female student nurses were examined. 45% had TrPs in masseter, 35% had TrPs in trapezious. 28% had myofascial pain at the time of examination.

Lumbogluteal muscles: Assessment of 100 asymptomatic control subjects. Revealed latent TrPs in 45% of Quadratus Lumborum, 41% of Gluteus Medius, 11% of Gluteus Minimus, 5% of Piriformis.

Patient Groups

Community pain medical center. 96 Patients studied by a neurologist: 93% had at least part of their pain caused by myofascial TrPs and in 74% of the patients myofascial TrPs were considered to be the primary source of Pain.

Comprehensive pain center: 283 consecutive admissions to a comprehensive pain center: The diagnosis made independently by a Neurosurgeon and a Physiatrist based on physical examination as described by Travell and Simons assigned a primary organic diagnosis of myofascial pain in 85% of the cases.

Additionally several studies have determined that MTrPs are frequently associated with and contribute to the patient's pain in the conditions summarised in the table below.

 

Diagnosis

Number

% with MTrPs

Source

Cervicogenic Headache

80

100%

Lin et al

Reflex Sympathetic Dystrophy

84

82%

Lin et al

Fibromyalgia

19

100%

Finestone et al

Chronic Intractable Benign Back Pain

90

96.7%

Rosomoff et al

Chronic Intractable Benign Neck Pain

34

100%

Rosomoff et al

Myofascial Pain Syndromes- Clinical Features

History of spontaneous pain associated with acute overload or chronic overuse of the muscle. The mildest symptoms are caused by latent MTrPs that cause no pain but cause some degree of functional disability. More severe involvement results in pain related to the position or movement of the muscle. The most severe level involves pain at rest.

Spot Tenderness: A very tender small spot, which is found in a Taut Band.

A taut band: A ropelike swelling found within the muscle probably due to sustained shortening of muscle fibers. Increasing the tension on the muscle fibers of the taut band can increase the sensitivity of the MTrP.

Jump Sign: Pressure on the tender spot causes the patient to physically react to the precipitated pain by exclaiming or moving. This reaction indicates the level of tenderness but is also dependent on the pressure exerted by the examiner.

Pain Recognition: Digital pressure on or needling of the tender spot induces / reproduces some of the patient's pain complaint and is recognised by the patient as being some or all of his or her pain.

This finding by definition identifies an active trigger point.

(This replication of the patient's pain may require sustained pressure (5 - 60 seconds) on the MTrP.)

Twitch Response: A transient contraction of the muscle fibers of the taut band containing the trigger point. The twitch response can be elicited by "snapping" palpation of the trigger point. Or more commonly by precise needling of the trigger point.

Elicited referred pain: An active MTrP refers pain in a pattern characteristic of that muscle -Usually to a site distant to the MTrP. 85% of TrPs project distally. [The area of the referred pain is often tender and may contain satellite trigger points.]

Latent TrPs also refer pain on pressure but usually require more pressure to do so.

Restricted Range of Movement: Full stretching of the affected muscle is often involuntarily restricted by pain.

Muscle Weakness: The patient is unable to demonstrate normal muscle strength on static testing of the affected side as compared to the contralateral non-affected side. The involved muscle is also more easily fatigued.

Pathogenic factors

Acute overload

Overwork - Fatigue (Including postural stress)

Chilling

Gross Trauma

Other Trigger Points

Emotional distress

Joint or nerve damage

Visceral disturbance

 

Perpetuating Factors

Mechanical: Structural Inadequacies e.g. The short leg syndrome, the small hemipelvis, the long second metatarsal, short upper arms.

Clothes. Tight constrictive clothing can produce MTrPs due to sustained muscle compression. E.g. Jeans related buttock pain, Bra strap headache, and wallet sciatica.

Systemic. Metabolic, endocrine, toxic, inflammatory etc.

Commonly found systemic factors include Hypothyroidism, folic acid and Iron deficiency.

Toxic: alcohol.

Metabolic - Inflammatory: gout.

Relative Growth Hormone deficiency has recently been suggested as playing a pivotal role in MTrPs syndromes.( As growth hormone is necessary for muscle repair and its secretion is related to deep sleep which is frequently disturbed in patients with pain. )

The Nature of Myofascial Trigger Points

The Histology of the Trigger Point is unremarkable.

Most modern studies have shown signs consistent with oxidative stress. [Implicating abnormal activity as opposed to gross anatomical change]

At present there are three major hypotheses:

The Energy crisis theory

The muscle spindle concept

The motor endplate hypothesis

Myofascial Trigger Points Diagnostic factors

MTrPs have specific pain referral patterns.

The actual trigger point is frequently outside the area of the patient's perceived pain.

Trigger point activity stimulates regional / segmental sympathetic outflows.

The area of the perceived (referred) pain is usually cool or cold.

The muscle containing the active Trigger Point is frequently found by recognising the Patient's Pain Pattern.

Comparison of the patient's pain diagram with Travell and Simons' trigger point charts greatly aids diagnosis.

Myofascial Trigger Points Emerging Criteria for Diagnosis:

Circumscribed local tenderness

Patient recognition

Jump sign

Local twitch response

Taut band

 

The Trigger Point Story - Where East Meets West

"Where there is a painful spot, there is an Acupuncture point" from the Neijing- The Yellow Emperor's Classic -1,000+ B.C.

When pressed on the Patient winces, or suddenly starts and exclaims "AAGH Is The POINT!" From Acupuncture a Comprehensive Text: Shanghai College of Traditional Chinese medicine.

Ah Shi - Oh Yes! as the patient's pain complaint is reproduced by palpation. Nanking College of Traditional Chinese Medicine, Nanking, China 1978.

Traditional Chinese Medicine's pathogenic factors include

Over-exertion

Invasion by "Cold" E.g. Chilling of a muscle by wind or cold following exertion.

Prolonged Inactivity

Visceral disturbance

TCM groups the Myofascial Pain Syndromes under the heading of Cold Bi syndromes. These syndromes have these common characteristics: Inhibition of blood supply, fondness and alleviation of pain with warmth and a worsening of the pain severity with cold and damp.

Traditional Chinese Medicines aim in the treatment of Cold Bi is to remove the obstruction to the flow of Chi and blood and warm and nourish the tissues.

In Western terms, remove the trigger point and its associated muscle spasm/shortening, diminish the over active sympathetic outflows and thereby restore normal blood flow.

The Near and Far method of Acupuncture, where the trigger point, and distal analgesia producing sympatholytic acupuncture points below the elbow or knee are needled, is an ancient method for the treatment of Myofascial pain syndromes that is currently used in China today.

The Bu needling technique or the warming method, where the needle is painlessly inserted and gently manipulated until needle grasp is obtained causes stimulation of large fibre afferents . The consequences of large fibre afferent activity are inhibition of small fibre activity (pain gate), relaxation of segmental muscle tone (muscle gate), and inhibition of sympathetic segmental outflow (sympathetic gate).

The exact effects of trigger point needling are not known. Relaxation of 'stuck' myofibrils, segmental release of encephalin and dynorphin, and localised trauma induced vasodilatation have all been postulated to explain the conversion of an exquisitely tender circumscribed muscle area to normal.

The effect of needling the analgesia producing distal points (points that are either muscle motor points or have dense cutaneous / muscle nerve innervation) has been well researched. The analgesic effects are mediated by the Endogenous Opiod substances as well as a host of other neurotransmitters and modulators including 5HT, and Nor Adrenalin. The sympatholytic effects of Acupuncture have been well detailed and have been shown to be associated with decreased pain scores in both sympathetically maintained and trigger point related pain states.

The success of the Near and Far Acupuncture technique and indeed of most treatment techniques that target the trigger point relies on the accurate localisation of the relevant trigger point. Consequently a rigorous physical examination including palpation must be carried out.

Treatment

The effective Rx of Myofascial Pain rests with defining the tissue and or reflex that is maintaining the Pain State. I.e. find the 'Active Trigger Points' and assess sympathetic involvement.

However, before being able to effectively treat Myofascial Pain syndromes (and evaluate that treatment's efficacy) the Trigger Point must first be identified, quantified and its associated reflexes delineated. Pressure Algometry, Thermography and EMG studies as well as electrical stimulation for pain provocation studies and differential local anaesthetic blocks, have been used with varying success to provide objective measurement of Trigger Point activity. Additionally much can be gained in clinical practice by the use of subjective pain assessment tools including, Visual Analogue pain Scales, The McGill Pain Questionnaire and Pain Diagrams.

The wide importance of Pain Assessment is highlighted by the following statement: "One of the most dramatic developments in pain research and therapy has been the recent proliferation of techniques for the measurement and assessment of Pain", R. Melzack

My own view is that, "Every patient complaining of chronic pain deserves to be examined. Palpation and the utilisation of pain assessment tools including, Pain Diagrams, the McGill Pain Questionnaire, Visual Analogue Pain Scale are all a necessary part of this process. And should always be carried out before referral for Psychologically based therapies. Simon Strauss unsubstantiated opinion.

Myofascial Pain Syndrome Assessment- Primary care practitioners Tool Kit

Subjective

Visual Analogue Scale (VAS)

McGill Pain Questionnaire

Pain Diagram

Objective

Pressure Threshold Algometry

Differential Local Anesthetic Blocks

Thermography, EMG etc.

Treatment Efficacy

Controlled trials have shown; dry needling, Acupuncture (The Near and Far technique), trigger point injection with saline, steroids, local anesthetics and Botulinum Toxin, to be effective treatment strategies. Biofeedback and Dental Splints have also proven to be effective in the context of Myofascial Tempero-Mandibular Joint Syndromes. The case for Spinal Manipulation and Low-Level Laser irradiation has not yet been established.