Immediate changes after manual therapy in resting-state functional connectivity as measured by functional magnetic resonance imaging in participants with induced low back pain

Abstract

Objective: The purposes of this study were to use functional magnetic resonance imaging to investigate the immediate changes in functional connectivity (FC) between brain regions that process and modulate the pain experience after 3 different types of manual therapies (MT) and to identify reductions in experimentally induced myalgia and changes in local and remote pressure pain sensitivity.

Methods: Twenty-four participants (17 men; mean age ± SD, 21.6 ± 4.2 years) who completed an exercise-injury protocol to induce low back pain were randomized into 3 groups: chiropractic spinal manipulation (n = 6), spinal mobilization (n = 8), or therapeutic touch (n = 10). The primary outcome was the immediate change in FC as measured on functional magnetic resonance imaging between the following brain regions: somatosensory cortex, secondary somatosensory cortex, thalamus, anterior and posterior cingulate cortices, anterior and poster insula, and periaqueductal gray. Secondary outcomes were immediate changes in pain intensity, measured with a 101-point numeric rating scale, and pain sensitivity, measured with a handheld dynamometer. Repeated-measures analysis of variance models and correlation analyses were conducted to examine treatment effects and the relationship between within-person changes across outcome measures.

Results: Changes in FC were found between several brain regions that were common to all 3 MT interventions. Treatment-dependent changes in FC were also observed between several brain regions. Improvement was seen in pain intensity after all interventions (P < .05) with no difference between groups (P > .05). There were no observed changes in pain sensitivity, or an association between primary and secondary outcome measures.

Conclusion: These results suggest that MTs (chiropractic spinal manipulation, spinal mobilization, and therapeutic touch) have an immediate effect on the FC between brain regions involved in processing and modulating the pain experience. This suggests that neurophysiologic changes after MT may be an underlying mechanism of pain relief.

Keywords: Chiropractic; Magnetic Resonance Imaging; Musculoskeletal Manipulations; Neurophysiology Brain.

Conflict of interest statement

CONFLICTS OF INTEREST

No conflicts of interest were reported for this study.

Copyright © 2014 National University of Health Sciences. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Functional connectivity is defined as the temporal correlation of a neurophysiological index measured in different brain areas. This term has been applied to functional magnetic resonance imaging, where the changes in BOLD signal over time are compared between two regions of interest (ROI). The correlation between the time series equals the estimated functional connectivity.

Figure 2

The data used for this study was obtained from a subgroup of volunteers derived from the pre-clinical trial.

Figure 3

A. Following manual therapy (MT), a decrease in functional connectivity (FC) between the left somatosensory cortex (SI) and the right posterior insula (pINS) was observed. B. The left anterior insula (aINS) and left posterior cingulate cortex (PCC) showed increased FC over time. C. Following MT, the left posterior insula (pINS) and left periaqueductal grey (PAG) showed increased FC

Figure 4

A. The change in functional connectivity (FC)between the right anterior insula (aINS) and right somatosensory cortex (SI) differed across the three MT groups. The spinal manipulative therapy (SMT) group showed an increase (Δ = 0.28), while the spinal mobilization group (MOB) (Δ = −0.04) and the therapeutic touch group (TT) (Δ = −0.14) showed decreases in FC. B. The FC changes between the right anterior insula (aINS) and left posterior cingulate cortex (PCC) differed across the three MT groups. The SMT group (Δ = 0.21) and the MOB (Δ = 0.05) showed an increases, while the TT group (Δ = −0.06) showed a decrease. C. The FC changes between the right somatosensory cortex (SI) and right periaqueductal grey (PAG) increased in the SMT (Δ = 0.04) and MOB (Δ = 0.19) groups, while FC decreased in the TT group (Δ = −0.17).