Abstract
BackgroundCompression of myofascial trigger points (MTrPs) in muscles is reported to reduce chronic musculoskeletal pain. Although the prefrontal cortex (PFC) is implicated in development of chronic pain, the mechanisms of how MTrP compression at low back regions affects PFC activity remain under debate. In this study, we investigated effects of MTrP compression on brain hemodynamics and EEG oscillation in subjects with chronic low back pain.MethodsThe study was a prospective, randomized, parallel-group trial and an observer and subject-blinded clinical trial. Thirty-two subjects with chronic low back pain were divided into two groups: subjects with compression at MTrPs (n = 16) or those with non-MTrPs (n = 16). Compression at MTrP or non-MTrP for 30 s was applied five times, and hemodynamic activity (near-infrared spectroscopy; NIRS) and EEGs were simultaneously recorded during the experiment.ResultsThe results indicated that compression at MTrPs significantly (1) reduced subjective pain (P < 0.05) and increased the pressure pain threshold (P < 0.05), (2) decreased the NIRS hemodynamic activity in the frontal polar area (pPFC) (P < 0.05), and (3) increased the current source density (CSD) of EEG theta oscillation in the anterior part of the PFC (P < 0.05). CSD of EEG theta oscillation was negatively correlated with NIRS hemodynamic activity in the pPFC (P < 0.05). Furthermore, functional connectivity in theta bands between the medial pPFC and insula cortex was significantly decreased in the MTrP group (P < 0.05). The functional connectivity between those regions was positively correlated with subjective low back pain (P < 0.05).DiscussionThe results suggest that MTrP compression at the lumbar muscle modulates pPFC activity and functional connectivity between the pPFC and insula, which may relieve chronic musculoskeletal pain.Trial registrationThis trial was registered at University Hospital Medical Information Network Clinical Trials Registry (UMIN000033913) on 27 August 2018, at https://upload. umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000038660.
Highlights
Chronic musculoskeletal pain is a substantial health concern, which may lead to worsening of daily living activities over time (Nakamura et al, 2011; Sugai et al, 2017)
The present study investigated the neural mechanisms of analgesic effects of myofascial trigger point (MTrP) compression in chronic low back pain using near infrared spectroscopy (NIRS) and EEG measurement
Both NIRS and EEG results indicated that MTrP compression significantly decreased activity in the polar area in the PFC (pPFC), as well as decreased functional connectivity between the pPFC and insula cortex, the strength of which between those regions was negatively correlated with subjective low back pain
Summary
Chronic musculoskeletal pain is a substantial health concern, which may lead to worsening of daily living activities over time (Nakamura et al, 2011; Sugai et al, 2017). It is noted that prolonged nociceptive inputs from MTrPs induce plastic changes in the brain, resulting in development and maintenance of chronic musculoskeletal pain (Niddam, 2009; Hocking, 2013; Shah et al, 2015). These findings suggest that analgesic effects of MTrP compression may be mediated through its effects on the central nervous system. Compression of myofascial trigger points (MTrPs) in muscles is reported to reduce chronic musculoskeletal pain. We investigated effects of MTrP compression on brain hemodynamics and EEG oscillation in subjects with chronic low back pain
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