It is not sufficiently well recognised that the reflex sympathetic dystrophy syndrome (RSDS) and the myofascial pain syndrome (MPS) may develop concomitantly. This happens because they have similar aetiological factors, with trauma being by far the commonest.
Everyone is liable to develop nociceptor pain as a result of trauma-induced activation and sensitisation of C afferent skin and Group IV muscle nociceptors; also A-β mediated pain as a result of the sensory afferent barrage produced by these nociceptors giving rise to sensitisation of dorsal horn transmission neurones.
With most people these neural changes lead only to the development of MPS. In a minority of people, possibly those with a genetically determined predisposition, this sensory afferent barrage also causes changes to take place in the sympathetic nervous system, with the development of a characteristic burning type of sympathetically mediated pain. This may develop alone or in association with myofascial trigger point pain.
There is much controversy concerning the mechanisms for development of RSDS pain. One theory is that the pain develops as a result of the nociceptor-induced sensory afferent barrage setting up aberrant sympathetic efferent activity. This results in the release of noradrenaline which binds to α-1 adrenoreceptors in the walls of the nociceptors, exciting them further. Much research, however, still has to be done before the development of sympathetically maintained pain can be adequately explained.
It is stressed that for the successful treatment of RSDS early diagnosis is essential. Treatment involves sympathetic blockade either by the injection of local anaesthetic into a sympathetic ganglion, or by the regional infusion of a catecholamine depleting drug.
Sympathetically maintained pain is morphine resistant and is therefore unlikely to be relieved by acupuncture, the analgesic effect of which is mediated by opioid peptides. The main place for acupuncture is in the treatment of concomitant myofascial trigger point pain.
It is emphasised that in all cases of RSDS it is essential to search for myofascial trigger points and, when present, to deactivate these by means of acupuncture stimulation of A-δ nerve fibres present in the skin and subcutaneous tissues at the trigger point sites.
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