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.

Antinociceptive Effects of Spinal Manipulative Therapy on Nociceptive Behavior of Adult Rats during the Formalin Test

“…In concert with these inhibitory afferent mechanisms or independently, descending pain inhibitory systems [ 77 , 78 ] also may be involved. Clinical research using functional magnetic resonance imaging in asymptomatic individuals has demonstrated that decreased remote peripheral pain rating immediately following spinal manipulative therapy was significantly related to reduced neuronal activation in brain regions associated with pain [ 92 ].…”

Effect of Spinal Manipulation Thrust Duration on Trunk Mechanical Activation Thresholds of Nociceptive-Specific Lateral Thalamic Neurons

“…Human imaging studies have begun to investigate brain correlates of a counterirritation phenomenon thought to be associated with manual therapy intervention. 32,33 For example, a counterirritation stimulus consisting of immersing the left contralateral foot in cold water decreased pain-related activation of several brain areas including the thalamus, primary somatosensory cortices, anterior cingulate cortex, and posterior insular cortex evoked by phasic electrical stimulation of the sural nerve in healthy volunteers. 61 Functional magnetic resonance imaging was used in a recent case series study to determine supraspinal activation in response to noxious mechanical stimuli applied before and after spinal manipulation.…”

Using Functional Magnetic Resonance Imaging to Determine if Cerebral Hemodynamic Responses to Pain Change Following Thoracic Spine Thrust Manipulation in Healthy Individuals

“…Manipulation has been postulated to have hypoalgesic effects on local and distant areas of pain, 61 and we have examined the global hypoalgesic effects of thoracic manipulation. The reasons for the use of thoracic spine manipulation with noxious mechanical stimulation to the index finger, as opposed to cervical spine manipulation, are 2-fold: first, it is not possible to manipulate the cervical spine without imparting some head-neck motion in the x, y, and z directions (in/ out and along the main magnetic field).…”