Supraspinal structures may be associated with hypoalgesia following thrust manipulation to the spine: a review of the literature

Abstract

Background: Thrust manipulation to the spine has been shown to be an effective treatment for pain reduction associated with musculoskeletal disorders. However, the mechanisms of action tied to this intervention have yet to be sufficiently explained.

Objectives: This manuscript reviews the literature related to supraspinal mechanisms associated with pain inhibition, which may also be associated with hypoalgesia following spinal manipulation. Such information adds to the current body of evidence that has demonstrated centrally mediated hypoalgesic effects following manipulation to be influenced by both dorsal horn inhibition and patient expectation.

Major findings: Areas believed to be responsible for processing pain include the amygdala, anterior cingulate, thalamus, insula, cerebellum, primary and secondary somatosensory cortices, periaqueductal grey, or dorsal horn. The periaqueductal grey receives information from spinoreticular and spinomesencephalic pathways in the spinal cord, as well as descending information from the amygdala and cortex. The inhibition of sensory stimuli in the dorsal horn may result in decreased projection of ascending information to the periaqueductal grey and modulation from higher-level cortical structures. Neuroimaging research in animals has demonstrated activation of such cortical structures in response to pain with subsequent decreased activation of these areas following joint mobilization. Researchers have yet to identify supraspinal structures associated with spinal manipulation in human subjects.

Conclusions: Future investigation should strive to identify supraspinal structures activated in human subjects following thrust manipulation. The identification of cortical and subcortical structures associated with hypoalgesia following spinal manipulation may influence the acceptance and use of this intervention with patients when indicated.

Keywords:

• Hypoalgesia
• Manipulation
• Manual therapy
• Pain
• Neuroimaging