Goossens N1, Janssens L1,2, Caeyenberghs K3, Rummens S4,5, Dierckx S1, Sunaert S6, Brumagne S1
1KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium, 2Hasselt University, Biomedical Research Institute (BIOMED) REVAL, Hasselt, Belgium, 3Australian Catholic University, School of Psychology, Melbourne, Australia, 4KU Leuven, Department of Development and Regeneration, Leuven, Belgium, 5University Hospitals Leuven, Department of Physical and Rehabilitation Medicine, Leuven, Belgium, 6KU Leuven, Department of Imaging & Pathology, Leuven, Belgium
Background: The global prevalence and disability of non-specific low back pain (NSLBP) increased markedly over the past decades. However, the mechanisms underlying NSLBP are still poorly understood, hampering the ability of healthcare professionals to provide targeted care. Previous research demonstrated that a poorer ability for proprioceptive weighting during postural control might be important in the development of NSLBP. During complex postural conditions, patients with NSLBP predominantly relied on ankle proprioception, and were less able to up-weigh back proprioception compared to pain-free controls. This poorer ability for proprioceptive weighting in NSLBP might be associated with an altered processing of proprioceptive signals in the brain. However, to date, this remained to be demonstrated.
Purpose: This study investigated
(1) differences in brain activation during the processing of ankle and back proprioception between individuals with and without NSLBP, and
(2) associations between proprioception-related brain activation and the ability for proprioceptive weighting during postural control.
Methods: Twenty patients with NSLBP and 20 matched pain-free controls participated. Brain activation during proprioceptive processing was determined by applying muscle vibration to the triceps surae (“ankle”) and lumbar paraspinal muscles (“back”) during functional magnetic resonance imaging (fMRI). Muscle vibration was applied at 60 Hz (blocks of 18s) to strongly stimulate muscle spindles and vibrotactile skin receptors, and at 20 Hz (blocks of 18s) to only stimulate skin receptors. Statistical Parametric Mapping (SPM12) was used to model vibration-induced changes in brain activation. Contrast images for 60 Hz > 20 Hz vibration were calculated to determine brain activation during proprioceptive processing. Group differences in proprioception-related brain activation were determined using a region-of-interest (ROI) approach. Moreover, linear regression analysis was performed to investigate associations with proprioceptive weighting during postural control. The significance threshold was set at p 0.05, family-wise error corrected over pre-defined ROIs.
Results: Patients with NSLBP demonstrated significantly increased activation in the right inferior frontal gyrus (IFG) and primary motor cortex (M1) during the processing of ankle proprioception compared to healthy individuals. This increased activation in the right IFG correlated with a more optimal weighting of proprioception during postural control in the patients with NSLBP. Moreover, during the stimulation of back proprioception, increased activation of the right amygdala and left superior frontal gyrus was found in the patients with NSLBP compared to the healthy group.
Conclusion(s): During ankle proprioceptive processing, patients with NSLBP over-activated brain areas that contribute to the lower-level and higher-order processing of proprioception (i.e., M1, IFG), possibly indicating a compensation mechanism to support optimal postural control in NSLBP. Moreover, patients with NSLBP over-activated fear-related brain regions involved in the detection and emotional processing of sensory inputs, suggesting an increased threat detection and hypervigilance towards stimuli applied at the painful body part.
Implications: Our findings emphasize that NSLBP may not be solely driven by peripheral mechanisms. Instead, management of NSLBP should include diagnostic and therapeutic strategies targeted towards central neural correlates. Future studies are needed to determine which treatment interventions are most effective to normalize neural changes in NSLBP.
Keywords: Non-specific low back pain, Proprioception, Brain activation
Funding acknowledgements: Funded by Flanders Innovation and Entrepreneurship (VLAIO) (Doctoral grant Nina Goossens), and Research Foundation Flanders (FWO) (Postdoctoral Fellowship Lotte Janssens).
Purpose: This study investigated
(1) differences in brain activation during the processing of ankle and back proprioception between individuals with and without NSLBP, and
(2) associations between proprioception-related brain activation and the ability for proprioceptive weighting during postural control.
Methods: Twenty patients with NSLBP and 20 matched pain-free controls participated. Brain activation during proprioceptive processing was determined by applying muscle vibration to the triceps surae (“ankle”) and lumbar paraspinal muscles (“back”) during functional magnetic resonance imaging (fMRI). Muscle vibration was applied at 60 Hz (blocks of 18s) to strongly stimulate muscle spindles and vibrotactile skin receptors, and at 20 Hz (blocks of 18s) to only stimulate skin receptors. Statistical Parametric Mapping (SPM12) was used to model vibration-induced changes in brain activation. Contrast images for 60 Hz > 20 Hz vibration were calculated to determine brain activation during proprioceptive processing. Group differences in proprioception-related brain activation were determined using a region-of-interest (ROI) approach. Moreover, linear regression analysis was performed to investigate associations with proprioceptive weighting during postural control. The significance threshold was set at p 0.05, family-wise error corrected over pre-defined ROIs.
Results: Patients with NSLBP demonstrated significantly increased activation in the right inferior frontal gyrus (IFG) and primary motor cortex (M1) during the processing of ankle proprioception compared to healthy individuals. This increased activation in the right IFG correlated with a more optimal weighting of proprioception during postural control in the patients with NSLBP. Moreover, during the stimulation of back proprioception, increased activation of the right amygdala and left superior frontal gyrus was found in the patients with NSLBP compared to the healthy group.
Conclusion(s): During ankle proprioceptive processing, patients with NSLBP over-activated brain areas that contribute to the lower-level and higher-order processing of proprioception (i.e., M1, IFG), possibly indicating a compensation mechanism to support optimal postural control in NSLBP. Moreover, patients with NSLBP over-activated fear-related brain regions involved in the detection and emotional processing of sensory inputs, suggesting an increased threat detection and hypervigilance towards stimuli applied at the painful body part.
Implications: Our findings emphasize that NSLBP may not be solely driven by peripheral mechanisms. Instead, management of NSLBP should include diagnostic and therapeutic strategies targeted towards central neural correlates. Future studies are needed to determine which treatment interventions are most effective to normalize neural changes in NSLBP.
Keywords: Non-specific low back pain, Proprioception, Brain activation
Funding acknowledgements: Funded by Flanders Innovation and Entrepreneurship (VLAIO) (Doctoral grant Nina Goossens), and Research Foundation Flanders (FWO) (Postdoctoral Fellowship Lotte Janssens).
Topic: Musculoskeletal: spine
Ethics approval required: Yes
Institution: KU Leuven
Ethics committee: Ethics Committee Research UZ/KU Leuven
Ethics number: S53802
All authors, affiliations and abstracts have been published as submitted.
