MPS is a noninflammatory disorder of musculoskeletal origin, associated with pain and muscle stiffness, characterized by the presence of hyperirritable palpable nodules in the skeletal muscle fibers, which are termed MTrPs. These trigger points are the cardinal feature of MPS and hence differentiate it from other painful MPSs such as inflammatory myositis and fibromyalgia. (Saxena et al, 2015).
MTrP is a hyperirritable spot in a taut band of a skeletal muscle, which is painful on compression, stretch, overload, or contraction of the muscle and usually has a distinct referred pain pattern.
Pathophysiology of MTrPs: The integrated hypothesis is the most accepted theory for explaining the pathophysiology of MTrP. It proposes that MTrPs occur as a result of an abnormal acetylcholine release at the level of a dysfunctional motor endplate resulting in sustained contractile activity of skeletal muscle fibers. The continued contractions, in turn, lead to the depletion of ATP, the release of pro-inflammatory substances, ischemia, and the localized hypoxic energy crisis which is associated with sensory and autonomic reflex arcs that are maintained by complex sensitization mechanisms.
Classification of MTrPs:
Active TrP: produces 2 types of pain
Latent TrP: may have all the other clinical characteristics of an active TrP with the main difference being painful only if palpated or compressed.
Mechanical stimulation of MTrPs can elicit different responses
MPS is diagnosed by muscle palpation and identification of the presence of myofascial trigger points and associated familiar pain. The manual palpation force can be established and performed efficiently by using a pressure algometry (usually between 2-4 kg/cm²).
When a trigger point in a taut band is suspected and located, the pressure of palpation over the TrP should be maintained for 10-20 seconds to determine if a pattern of pain referral is elicited.
When the source of pain is difficult to identify, a diagnostic anesthetic injection delivered to the trigger point can be very helpful to confirm the diagnosis. (Okeson et al, 2013).
Differential diagnosis of MPS
The main goal of MPS management is to decrease or eliminate pain symptoms, increase mouth opening to normal and improve the quality of life.
1- Nonpharmacological treatments:
2- Pharmacological treatments:
References:
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