3Myofascial pain syndromes and their evaluation
Section snippets
Definitions
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Myofascial pain: pain arising from muscles or related fascia.
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Active trigger point: an active trigger point causes spontaneous pain at rest, with an increase in pain on contraction or stretching of the muscle involved. There is often a restriction of its range of motion. Pain on motion may cause ‘pseudo-muscle weakness’ due to reflex inhibition (Table 1).
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Latent trigger point: a latent trigger point is a focal area of tenderness and tightness in a muscle that does not result in spontaneous pain.
Prevalence
It has been estimated that some 44 million Americans have myofascial pain problems.5 A study from an internal medicine group practice found that 30% of patients with pain complaints had active myofascial trigger points.6 A report from a clinic specializing in head and neck pain reported a myofascial etiology in 55% of cases.7 Patients evaluated in one pain management center were found to have a myofascial component to their pain in 95% of cases.8 There is increasing awareness that active
The key elements in the case history suggesting a diagnosis of myofascial pain
The possibility that there may be myofascial syndrome should be considered in any patient in whom a well-defined etiology for their pain cannot be found. The clinical diagnosis of myofascial pain is dependent on the physician being aware of this diagnosis as a possible cause for the patient's pain complaint.3 In a patient with a recent muscle injury or symptoms of repetitive strain the possibility of a myofascial component is self-evident. In a patient with a focal pain complaint that cannot be
The key elements in the physical examination of suspected myofascial pain
Rheumatologists are well trained in the diagnosis of arthritis, tendonitis and bursitis, but usually lack training in the diagnosis of myofascial pain syndromes. Myofascial pain syndromes may mimic a large number of other disorders20; furthermore, the finding of myofascial trigger points does not rule out other conditions. Thus, a general history and physical examination is, as always, a prerequisite for a competent and informed diagnosis.
Examining for the presence of myofascial trigger points
Reliability of Diagnosis
There are no well-validated diagnostic criteria for the identification of trigger points. The usual recommendations for identifying a trigger point specify that gentle palpation should be performed across the direction of the muscle fibers in order for the examiner to identify a longitudinal region of nodularity (i.e. the taut band). If the taut band can be ‘snapped’, a local contraction of the muscle may be observed (i.e. ‘the twitch response’). The patient's response to these maneuvers is a
Experimental Muscle Pain
The pioneering studies of experimental myofascial pain were performed by a future rheumatologist, Jonas Henrik Kellgren, when he was a student of Sir Thomas Lewis at University College Hospital, London, UK. Lewis was interested in the precise localization of pain by a skin stimulus, whereas pain from deeper structures was not so accurately localized. In the 1930s it was assumed that most cutaneous pain resulted from a ‘neuritis’, and Lewis challenged this explanation by experiments using
Histological, Neurophysiological and Biochemical Findings
The precise pathophysiological basis for the trigger point phenomenon is still not fully understood, but there is emerging evidence for abnormal neurophysiology and a perturbed biochemical milieu being relevant to the histological finding of ‘contracture knots’.
Common Clinical Syndromes of Myofascial Pain
A myofascial pain syndrome may be due to just one trigger point, but more commonly there are several trigger points responsible for any given regional pain problem. It is not uncommon for the problem to be initiated with a single trigger point, with the subsequent development of satellite trigger points that evolve over time due to the mechanical imbalance resulting from the reduced range of movement and pseudo-weakness. The persistence of a trigger point may lead to neuroplastic changes at the
Prognosis
Uncomplicated myofascial pain syndromes usually resolve with appropriate correction of predisposing factors and myofascial treatment.72 If the symptoms are persistent, due to ineffective management, the development of segmental central sensitization may lead to a stubbornly recalcitrant pain disorder. In some such cases, the spread of central sensitization leads to the widespread pain syndrome of fibromyalgia.4, 73
Treatment
The effective management of myofascial pain syndromes requires attention to the following issues*72, 74:
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