Autonomic Effects of Spinal Manipulative Therapy: Systematic Review of Randomized Controlled Trials

The purpose of this study was to systematically review the effects of spinal manipulative therapy (SMT) on autonomic nervous system (ANS)-mediated outcomes, in both symptomatic and healthy populations, and to assess the quality of evidence for the most prevalent outcomes with the Grading of Recommendations, Assessment, Development and Evaluation approach.

PubMed, Cochrane Library, PEDro, Web of Science, and EMBASE were searched from their inception to March 2014. Randomized controlled trials involving SMT, such as mobilization and manipulation, that reported at least 1 outcome related to the ANS, with placebo, control groups, or other SMT techniques as comparators, with either healthy or symptomatic samples were included. The Physiotherapy Evidence Database scale and the Grading of Recommendations, Assessment, Development and Evaluation approach were used to assess risk of bias and the quality of evidence, respectively.

Eighteen trials were included in this systematic review. Passive accessory intervertebral mobilization produced sympathoexcitation independently of the treated region (cervical, thoracic, or lumbar spine); although sustained natural apophyseal glides did not influence the ANS, conflicting results were observed regarding manipulation techniques. The overall quality of evidence for all analyzed outcomes ranged from low to very low quality.

There is evidence pointing toward the existence of sympathoexcitatory short-term effects following passive accessory intervertebral mobilization mobilizations, but not for sustained natural apophyseal glide mobilizations. There is conflicting evidence regarding the ability of manipulation to elicit sympathoexcitation. However, the low quality of the evidence precludes a definitive conclusion of such effects. Based on the current evidence, there is uncertainty regarding the true effect estimates of SMT on ANS-mediated outcomes.