Data Sources: MEDLINE search using key words: chiropractic, osteopathy, neurophysiology, review, spinal reflex, supraspinal reflex, manipulation.
Data Selection: The search resulted in more than 200 papers that fit the key words. Papers were selected on the basis that they contained relevant information on somatovisceral, viscerosomatic or supraspinal reflexes or treatment approaches relevant to the management of visceral disorders by spinal manipulative therapy.
Data Extraction: Ninety-four selected papers contained information that related to somatovisceral and viscerosomatic reflexes or on supraspinal influences on these reflexes.
Data Synthesis: A review of the proposed mechanisms of the effect of spinal manipulative therapy on visceral neurophysiology was conducted. The reflexes affect the resting status of the somatic structures via mechanical and neurological (somato-somatic reflex) mechanisms that can cause a change to the afferent arm of the somato-visceral reflex. Such changes can occur by the direct action of a somatovisceral effect at the segmental level, but the effect is minimised by the action of the supraspinal pathways in the integration of the reflexes. It is hypothesised that SMT may affect the supraspinal inhibitory and excitatory pathways to the preganglionic neurones, although this has not been demonstrated. There is scanty evidence of SMT affecting visceral disease through manipulation of the spine.
Conclusions: Spinal manipulative therapy can affect the resting status of somatic structures via mechanical and neurological (somato-somatic reflex) mechanisms, and this change can cause a change to the afferent arm of the somato-visceral reflex. It is likely that supraspinal influences play a major role in this effect, however the exact nature of this effect has not been demonstrated with respect to manipulation of the spine. Much research is required to establish a causative relationship between the treatment of somatic structures of the spine and normalisation of pathological visceral tissues via somatovisceral or supraspinal reflexes.
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