It must be reiterated that pain referral is the cardinal feature of the myofascial trigger point (MTrP). As such simply trying to identify a MTrP by the presence of a taut band and tender point is insufficient. The referred pain patterns generated by the MTrP usually, but not always, occur within a predictable distribution as described by Travell and Simon’s. If the referred pain is familiar to the patient, i.e reminds them of the symptoms for which the patient may have sought treatment, the MTrP may be considered active. If the referred pain is unfamiliar is may be considered latent, but arguably the MTrP may still be worth treating.
Is the referred pain phenomenon a peripheral or central effect?
Evidence has concluded that referred pain is most certainly a central effect. My understanding of this has mostly centred at the dorsal horn where a ‘wind up’ may occur in response the afferent nociceptive barrage arising from the MTrP. This results in a progressive pain referral mostly within the associated segment. This effect has been supported by studies which have shown MTrP’s in rats capable of sensitising the dorsal horn with the development of new neurons.
More recent evidence involving brain imaging studies would suggest the higher sensory centres are also involved in the production of referred pain arising from the MTrP. Of interest is how these activated regions are further increased and ‘spread’ in patients suffering from chronic pain conditions such as fibromyalgia.
From a clinical point of view, the extent of the central changes associated with referred pain arising from MTrP would, from my point of view, argue for early treatment. It may also explain how untreated MTrP may result in progressive central sensitisation possibly leading to fibromyalgia.
Take home message?
Encourage patients not to ignore persistent myofascial pain. This may involve self management strategies as well as seeking treatment if needed.