Myofascial pain syndrome
Abstract
Myofascial Pain syndrome (MPS) is a painful condition of the soft tissue in which discomfort originates from trigger points, muscles, tendons or fascia.
Little is known about the pathomechanism. However, local disturbances in blood-flow and biochemical environment have been reported.
Patients describe a deep, focal pain, which may refer to different sites of the body.
Although Robert D. Gerwin defined criteria for identifying MTrPs, there is no specific test which may confirm the diagnosis. It is much more a combination of these criteria and the absence of other clues, which lead to the right diagnosis.
MPS is treated with physical therapy. Patients are advised to strengthen weak muscle groups and most importantly to stretch affected areas. In addition to that, other treatment options might be: Massage therapy, dry needling, neuraltherapy, acupuncture and administration of NSAID or muscle relaxants.
General considerations
Definition
Myofascial pain syndrome (MPS) is a pathology of the soft tissue. Its underlying cause are myofascial trigger points (MTrP), which can be explained as small, localized areas of muscle contraction with explicit tenderness. You may also find increased muscle tone, tender tendons or fascia.
Features of the MTrP are clearly defined. They are always situated on a taut band of muscle, are always tender on palpation and refer pain to distant sites of the body leading to central sensitization and therefore lowering the pain threshold. Furthermore, they contract noticeably by applying mechanical stimulation (local twitch response) and lead to limitation when trying to stretch the affected muscle [1].
Aetiology
To this date, the exact pathological course of events remains unclear. On ultrasound, trigger points impress as hypoechoic regions with comparably low blood flow [4]. Measurements of extracellular fluid around MTrPs have shown a decrease in pH of 4 to 5 as well as a high concentration of inflammatory cytokines and neurotransmitters [4]. These visual, vascular, and biochemical changes are unique to trigger points, which are also regulated by the sympathetic nervous system, making them vulnerable to states of activated sympathetic nervous system such as stressful situations [4]. Several predisposing factors, such as mechanical and metabolic stress, have been identified. However, data does not fully support a causal connection.
Mechanical stress
Anomalities in posture
Scoliosis
leg-length inequality
Spondylosis
Nerve compression
Osteoarthritis
Hypermobility
Poor posture
Work-related
Repetitive motions
Metabolic stress
Hypometabolic states
Iron deficiency
Vitamin D- & B12-deficiency
Infectous diseases
Psychological stress (Yellow flags, Blue flags)
Anxiety
Epidemiology
Estimations of lifetime prevalence of any myofascial pain have been reported at around 85% [4]. In contrast to many other pain disorders, men have been found to be equally affected as women [3]. As it is not a common topic of research interest, there is insufficient data on shoulder specific MPS.
Clinical presentation
Patients suffering from MPS experience deep and dull aching pain that may refer to other distinct sites in the body. Trigger points can either be latent or active. In active trigger points, pain occurs spontaneously in contrast to latent trigger points, where pain is only felt on palpation [4]. Moreover, there might be symptoms of autonomic dysfunction such as diaphoresis, flushing, pilomotor activity or temperature change of the affected area. In a chronic course of disease lowered work tolerance, weakness and sleep disturbance may be present as well [3]. The concept of referred pain is always to be taken into consideration. Trigger points in the shoulder girdle refer pain into the neck region, shoulder or down to the arm. They can mimic or be the cause of certain pain syndromes such as nerve entrapment, fibromyalgia, different types of headaches, frozen shoulder as variant of CRPS, or lower back pain [4].
Diagnosis
History
The anamnesis should contain the different aspects of MPS such as:
Onset of pain
Chronic or acute
Referral of pain
Helps differentiate between the muscles affected
Quality of pain
History of predisposing factors
Disease specific diagnosis
In a paper published by MD Robert D. Gerwin in 2014, eight different features of MTrP are defined, which are presented hereafter:
Features of the myofascial trigger point [1]: the first 3 are essential for diagnosis; the last 5 are not required to make a diagnosis
1. Tight band within the muscle
2. Exquisite tenderness at a point on the tight band
3. Reproduction of the patient’s pain
4. Local twitch response
5. Referred pain
6. Weakness
7. Restricted range of motion
8. Autonomic signs (skin warmth, piloerection)
Gerwin also constructed a simple instruction, which should facilitate identifying trigger points:
Procedure for identifying trigger points [1]:
1. History and pain diagram: the history identifies the areas affected by pain
2. Examination of muscles whose trigger points can refer pain to the affected areas
3. Palpate the muscle for tight bands, using either flat palpation or pincer palpation
4. Move the fingers along the tight band to find the hardest and most tender spot (the trigger point)
5. Compress the trigger point manually and ask (1) if the spot is tender or painful, and if so, (2) does the pain resemble the patient’s usual pain
6. Compress the trigger point for 5–10 seconds and then ask if there is pain or some sensation away from the trigger point (referred pain)
Muscles affected that may refer pain to the shoulder are:
M. Trapezius
M. Supraspinatus
M. infraspinatus
M. Levator scapulae
M. Posterior serratus superior
M. Rhomboideus
M. Subscapularis
M. Teres major and minor
M. Latissimus dorsi
M. Deltoideus
M. Pectoralis major and minor
It should be noted that MPS cannot be diagnosed by examination only. There are several other conditions, which can mimic pain stemming from MTrP and vice-versa and should consequently be excluded from one’s differential diagnosis. Root compression or other neurologic pathologies should be addressed and examined. Laboratory tests should be used to rule out metabolic disturbances, which if present, should be the focus of treatment [3].
Differential Diagnosis
Polymyositis
Fibromyalgia
Polymyalgia rheumatica
Radiculopathy
Entrapment neuropathy
Metabolic myopathy
Diskogenic disorders
Treatment
There are different ways to approach treatment of MPS. Inactivation of active and latent trigger points is of utmost priority. To achieve inactivation and therefore reduce central sensitisation, manual as well as invasive procedures have proven successful. Both dry needling and injection of local anaesthetics are effective tools to inactivate MTrPs. Additionally, preventing predisposing factors should be taken into consideration. Physical therapy with focusing on strengthening weak muscle groups, fixing posture and most importantly stretching affected areas were also shown to reduce frequency of occurrence of MTrPs [3]. Moreover, psychological stress and addressing workplace ergonomics should complete the non-pharmacological treatment.
Pharmacological treatment on the other side ranges from NSAIDs and muscle relaxants to benzodiazepines (try to avoid or only short term use), selective serotonin reuptake inhibitors or even lidocaine patches. Pharmacological treatment should be evaluated individually for each patient, regarding his or her associated symptoms [3].
Prognosis and progressive course of disease
If predisposing factors persist, trigger points are likely to form again after inactivation [4]. Continuous inactivation however, may lead to a decrease in central sensitisation and patients may benefit on the longterm [4].
References
Gerwin, Robert D. 2014. "Diagnosis Of Myofascial Pain Syndrome". Physical Medicine And Rehabilitation Clinics Of North America 25 (2): 341-355. doi:10.1016/j.pmr.2014.01.011.
Bron, Carel, and Jan D. Dommerholt. 2012. "Etiology Of Myofascial Trigger Points". Current Pain And Headache Reports 16 (5): 439-444. doi:10.1007/s11916-012-0289-4.
Borg-Stein, Joanne, and Mary Alexis Iaccarino. 2014. "Myofascial Pain Syndrome Treatments". Physical Medicine And Rehabilitation Clinics Of North America 25 (2): 357-374. doi:10.1016/j.pmr.2014.01.012.
Gerwin, Robert. 2016. "Myofascial Trigger Point Pain Syndromes". Seminars In Neurology 36 (05): 469-473. doi:10.1055/s-0036-1586262.