Abstract
The objectives of the study were to investigate changes in pain perception and neural activity during tonic pain due to altered sensory input from the spine following chiropractic spinal adjustments. Fifteen participants with subclinical pain (recurrent spinal dysfunction such as mild pain, ache or stiffness but with no pain on the day of the experiment) participated in this randomized cross-over study involving a chiropractic spinal adjustment and a sham session, separated by 4.0 ± 4.2 days. Before and after each intervention, 61-channel electroencephalography (EEG) was recorded at rest and during 80 seconds of tonic pain evoked by the cold-pressor test (left hand immersed in 2 °C water). Participants rated the pain and unpleasantness to the cold-pressor test on two separate numerical rating scales. To study brain sources, sLORETA was performed on four EEG frequency bands: delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz) and beta (12–32 Hz). The pain scores decreased by 9% after the sham intervention (p < 0.05), whereas the unpleasantness scores decreased by 7% after both interventions (p < 0.05). sLORETA showed decreased brain activity following tonic pain in all frequency bands after the sham intervention, whereas no change in activity was seen after the chiropractic spinal adjustment session. This study showed habituation to pain following the sham intervention, with no habituation occurring following the chiropractic intervention. This suggests that the chiropractic spinal adjustments may alter central processing of pain and unpleasantness.
Highlights
Changes in the way the human brain processes pain, as well as the capacity to modulate the pain experience, underlies the pathogenesis of most chronic pain conditions1
Research has shown that chiropractic spinal adjustments alter the afferent input from the spine which leads to changes in central nervous system (CNS) function23
As it is becoming clear that chiropractors impact brain function consistently, it is very likely that chiropractic care influences the biomechanical movement patterns of the spine and improves proprioceptive processing of the spine33,34 and directly impacts the so called ‘pain matrix’ in the brain and has a conditioned pain modulation (CPM) effect on a person’s perception of pain
Summary
Changes in the way the human brain processes pain, as well as the capacity to modulate the pain experience, underlies the pathogenesis of most chronic pain conditions. Shao et al, using EEG and standardized low-resolution brain electromagnetic tomography (sLORETA), showed that tonic cold pain induced significant changes of source power across different frequency bands in many brain regions, including the prefrontal, primary and secondary somatosensory (S1 and S2), insular and cingulate cortices. Shao et al, using EEG and standardized low-resolution brain electromagnetic tomography (sLORETA), showed that tonic cold pain induced significant changes of source power across different frequency bands in many brain regions, including the prefrontal, primary and secondary somatosensory (S1 and S2), insular and cingulate cortices40 These same regions have been consistently shown to be activated or deactivated during pain perception by various neuroimaging studies using functional magnetic resonance imaging (fMRI), magnetoencephalography (MEG) and positron emission tomography (PET) (see e.g.7,41–43). These specific brain regions and frequency bands identified during the CP test were the 4–8 Hz (theta) oscillatory activity in the prefrontal cortex, the 8–12 Hz (alpha) oscillatory activity in the anterior cingulate cortex (ACC) and the 12–18 Hz (beta) oscillatory activity in the posterior cingulate cortex (PCC)
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