Evidence for decreased Neurologic Pain Signature activation following thoracic spinal manipulation in healthy volunteers and participants with neck pain.

BACKGROUND CONTEXT: Spinal manipulation (SM) is a common treatment for neck and back pain, theorized to mechanically affect the spine leading to therapeutic mechanical changes. The link between specific mechanical effects and clinical improvement is not well supported. SM's therapeutic action may instead be partially mediated within the central nervous system. PURPOSE: To introduce brain-based models of pain for spinal pain and manual therapy research, characterize the distributed central mechanisms of SM, and advance the preliminary validation of brain-based models as potential clinical biomarkers of pain. STUDY DESIGN: Secondary analysis of two functional magnetic resonance imaging studies investigating the effect of thoracic SM on pain-related brain activity: A non-controlled, non-blinded study in healthy volunteers (Study 1, n = 10, 5 females, and mean age = 31.2 ±â€¯10.0 years) and a randomized controlled study in participants with acute to subacute neck pain (Study 2, n = 24, 16 females, mean age = 38.0 ±â€¯15.1 years). METHODS: Functional magnetic resonance imaging was performed during noxious mechanical stimulation of the right index finger cuticle pre- and post-intervention. The effect of SM on pain-related activity was studied within brain regions defined by the Neurologic Pain Signature (NPS) that are predictive of physical pain. RESULTS: In Study 1, evoked mechanical pain (p < 0.001) and NPS activation (p = 0.010) decreased following SM, and the changes in evoked pain and NPS activation were correlated (rRM2 = 0.418, p = 0.016). Activation within the NPS subregions of the dorsal anterior cingulate cortex (dACC, p = 0.012) and right secondary somatosensory cortex/operculum (rS2_Op, p = 0.045) also decreased following SM, and evoked pain was correlated with dACC activity (rRM2 = 0.477, p = 0.019). In Study 2, neck pain (p = 0.046) and NPS (p = 0.033) activation decreased following verum but not sham SM. Associations between evoked pain, neck pain, and NPS activation, were not significant and less clear, possibly due to inadequate power, methodological limitations, or other confounding factors. CONCLUSIONS: The findings provide preliminary evidence that SM may alter the processing of pain-related brain activity within specific pain-related brain regions and support the use of brain-based models as clinical biomarkers of pain.

Functional Magnetic Resonance Imaging of Cerebral Hemodynamic Responses to Pain Following Thoracic Thrust Manipulation in Individuals With Neck Pain: A Randomized Trial.

OBJECTIVE: The purpose of this study was to examine whether cerebral activation in response to noxious mechanical stimuli varies with thrust manipulation (TM) when compared with sham manipulation (SM) as measured by blood oxygenation level-dependent functional magnetic resonance imaging. METHODS: Twenty-four volunteers (67% female) with complaints of acute or subacute mechanical (nontraumatic) neck pain satisfied eligibility requirements and agreed to participate. Participants were randomized to receive TM to the thoracic spine or SM, and then underwent functional magnetic resonance scanning while receiving noxious stimuli before and after TM or SM. An 11-point numeric pain rating scale was administered pre- and postmanipulation for neck pain and to determine perceptions of pain intensity with respect to neck pain and mechanical stimuli. Blood oxygenation level-dependent functional magnetic resonance imaging recorded the cerebral hemodynamic response to the mechanical stimuli. RESULTS: Imaging revealed significant group differences, with those individuals in the manipulation group exhibiting increased areas of activation (postmanipulation) in the insular and somatosensory cortices and individuals in the sham group exhibiting greater areas of activation in the precentral gyrus, supplementary motor area, and cingulate cortices (P < .05). However, between-group differences on the numeric pain rating scale for mechanical stimuli and for self-reported neck pain were not statistically significant. CONCLUSIONS: This study provides preliminary level 2b evidence suggesting cortical responses in patients with nontraumatic neck pain may vary between thoracic TM and a sham comparator.

Advancements in Imaging Technology: Do They (or Will They) Equate to Advancements in Our Knowledge of Recovery in Whiplash?

Synopsis It is generally accepted that up to 50% of those with a whiplash injury following a motor vehicle collision will fail to fully recover. Twenty-five percent of these patients will demonstrate a markedly complex clinical picture that includes severe pain-related disability, sensory and motor disturbances, and psychological distress. A number of psychosocial factors have shown prognostic value for recovery following whiplash from a motor vehicle collision. To date, no management approach (eg, physical therapies, education, psychological interventions, or interdisciplinary strategies) for acute whiplash has positively influenced recovery rates. For many of the probable pathoanatomical lesions (eg, fracture, ligamentous rupture, disc injury), there remains a lack of available clinical tests for identifying their presence. Fractures, particularly at the craniovertebral and cervicothoracic junctions, may be radiographically occult. While high-resolution computed tomography scans can detect fractures, there remains a lack of prevalence data for fractures in this population. Conventional magnetic resonance imaging has not consistently revealed lesions in patients with acute or chronic whiplash, a "failure" that may be due to limitations in the resolution of available devices and the use of standard sequences. The technological evolution of imaging techniques and sequences eventually might provide greater resolution to reveal currently elusive anatomical lesions (or, perhaps more importantly, temporal changes in physiological responses to assumed lesions) in those patients at risk of poor recovery. Preliminary findings from 2 prospective cohort studies in 2 different countries suggest that this is so, as evidenced by changes to the structure of skeletal muscles in those who do not fully recover. In this clinical commentary, we will briefly introduce the available imaging decision rules and the current knowledge underlying the pathomechanics and pathophysiology of whiplash. We will then acknowledge known prognostic factors underlying functional recovery. Last, we will highlight emerging evidence regarding the pathobiology of muscle degeneration/regeneration, as well as advancements in neuroimaging and musculoskeletal imaging techniques (eg, functional magnetic resonance imaging, magnetization transfer imaging, spectroscopy, diffusion-weighted imaging) that may be used as noninvasive and objective complements to known prognostic factors associated with whiplash recovery, in particular, poor functional recovery. J Orthop Sports Phys Ther 2016;46(10):861-872. doi:10.2519/jospt.2016.6735.