Neurophysiological effects of spinal manipulation

Neurophysiological effects of spinal manipulation

A ChiroSecure Research Update

Abstract: The purpose of this review article is to examine the neurophysiological basis for the effects of spinal manipulation

Discussion: Biomechanical changes caused by spinal manipulation are thought to have physiological consequences by means of their effects on the inflow of sensory information to the central nervous system. Muscle spindle afferents and Golgi tendon organ afferents are stimulated by spinal manipulation. Smaller-diameter sensory nerve fibers are likely activated, although this has not been demonstrated directly.

Mechanical and chemical changes in the intervertebral foramen caused by a herniated intervertebral disc can affect the dorsal roots and dorsal root ganglia, but it is not known if spinal manipulation directly affects these changes. Individuals with herniated lumbar discs have shown clinical improvement in response to spinal manipulation. The phenomenon of central facilitation is known to increase the receptive field of central neurons, enabling either subthreshold or innocuous stimuli access to central pain pathways. Numerous studies show that spinal manipulation increases pain tolerance or its threshold.

One mechanism underlying the effects of spinal manipulation may, therefore, be the manipulation’s ability to alter central sensory processing by removing subthreshold mechanical or chemical stimuli from paraspinal tissues.

Spinal manipulation is also thought to affect reflex neural outputs to both muscle and visceral organs. Substantial evidence demonstrates that spinal manipulation evokes paraspinal muscle reflexes and alters motoneuron excitability. The effects of spinal manipulation on these somatosomatic reflexes may be quite complex, producing excitatory and inhibitory effects. Whereas substantial information also shows that sensory input, especially noxious input, from paraspinal tissues can reflexively elicit sympathetic nerve activity, knowledge about spinal manipulation’s effects on these reflexes and on end-organ function is more limited.

Conclusion: A theoretical framework exists from which hypotheses about the neurophysiological effects of spinal manipulation can be developed. An experimental body of evidence exists indicating that spinal manipulation impacts primary afferent neurons from paraspinal tissues, the motor control system, and pain processing. Experimental work in this area is warranted and should be encouraged to help better understand mechanisms underlying the therapeutic scope of spinal manipulation.

Reference: Pickar JG. Neurophysiological effects of spinal manipulation. Spine J. 2002 Sep-Oct;2(5):357-71. doi: 10.1016/s1529-9430(02)00400-x. PMID: 14589467.