Sympathetic outflow unchanged after spinal manipulation in asymptomatic patients
MedWire News: Spinal manipulation applied to a hypomobile segment of the upper thoracic spine has no effect on plasma catecholamine levels in asymptomatic patients, report Canadian researchers.
Previous studies have shown that mechanical stimulation to spinal and paraspinal tissues results in a multitude of physiologic responses and it has been suggested that this may be mediated by the sympathetic nervous system (SNS), say Aaron Puhl and H Stephen Injeyan from the Canadian Memorial Chiropractic College in Toronto, Ontario.
Measuring plasma concentrations of the catecholamines norepinephrine (NE) and epinephrine (E) is an accepted method of gauging overall sympathetic and adrenal medullary activity, and plasma catecholamine levels are known to change in a matter of seconds in response to sympathetic stimulation, they explain.
The researchers therefore sought to investigate the short-term effects of spinal manipulation, applied to a hypomobile segment of the upper thoracic spine (T1-T6), on plasma concentrations of NE and E in 56 asymptomatic individuals aged between 20 and 45 years.
Participants were randomly assigned to receive either a chiropractic manipulative intervention or a sham intervention in the upper thoracic spine. Plasma NE and E concentrations were determined before, immediately after, and 15 minutes after the intervention. Plasma samples of 36 participants (18 treatment, 18 control) were used in the final analysis.
The researchers found that mean plasma concentrations of NE and E did not significantly differ between the spinal manipulation and sham groups at baseline (1.52 vs 1.57 and 0.29 vs 0.30 nM, respectively) or at either of the postintervention sample times (1.55 vs 1.59 and 0.33 vs 0.32 nM immediately after intervention; 1.58 vs 1.64 and 0.30 vs 0.30 nM 15 minutes after intervention, respectively). In addition, levels of NE and E did not change significantly over the course of the study.
"These findings suggest that there was no change to sympathetic outflow in these patients," explain the authors in the Journal of Manipulative and Physiological Therapeutics. "Although this study does not necessarily negate the theory that spinal manipulation can affect the SNS, it does indicate that catecholamine levels are not affected to a measurable extent by a thoracic manipulation in asymptomatic subjects."
Nonetheless, "this study provides a reliable baseline measure of catecholamine concentrations as well as the response of catecholamine concentrations to a thoracic manipulation in asymptomatic subjects."
Puhl and Injeyan say that their results should "inform the design of future studies of a similar nature" and "aid in the analysis of their results by providing a baseline response to manipulation."
They suggest that future research might "investigate the effects of spinal manipulation therapy on the catecholamine levels in symptomatic subjects with spinal dysfunction, where the basal activity of the SNS is more likely to be altered."
By Nikki Withers