Poster No:
1599
Submission Type:
Abstract Submission
Authors:
Monika Dörig1, David Cole2, Alexandros Guekos1, Philipp Stämpfli3, Philipp Schuetz4, Louis Schibli4, Petra Schweinhardt1, Michael Meier1
Institutions:
1Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital, Zurich, Switzerland, 2Department of Psychiatry (UPK), University of Basel, Basel, Switzerland, 3MR-Center of the Psychiatric Hospital, University of Zurich, Zurich, Switzerland, 4Competence Center Thermal Energy Storage, Lucerne University of Applied Sciences and Arts, Horw, Switzerland
First Author:
Monika Dörig
Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital
Zurich, Switzerland
Co-Author(s):
David Cole
Department of Psychiatry (UPK), University of Basel
Basel, Switzerland
Alexandros Guekos
Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital
Zurich, Switzerland
Philipp Stämpfli
MR-Center of the Psychiatric Hospital, University of Zurich
Zurich, Switzerland
Philipp Schuetz
Competence Center Thermal Energy Storage, Lucerne University of Applied Sciences and Arts
Horw, Switzerland
Louis Schibli
Competence Center Thermal Energy Storage, Lucerne University of Applied Sciences and Arts
Horw, Switzerland
Petra Schweinhardt
Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital
Zurich, Switzerland
Michael Meier
Integrative Spinal Research, Department of Chiropractic Medicine, Balgrist University Hospital
Zurich, Switzerland
Introduction:
Chronic low back pain (cLBP) is often associated with cortical plasticity in the primary sensorimotor cortices, where the somatotopic map may become "smudged" or less functionally discrete (Schabrun, 2017; Flor, 1997), potentially contributing to pain persistence (Brumagne, 2019; Vittersø, 2022). However, evidence for cortical map reorganization in cLBP is sparse, particularly regarding the sensory representation of the back in the primary somatosensory cortex (S1). While early studies on conditions like complex regional pain syndrome (CRPS) supported the cortical reorganization theory in chronic pain, a recent high-resolution functional magnetic resonance imaging (fMRI) study suggests that S1 somatotopic maps may remain preserved in CRPS (Mancini, 2019), challenging the cortical sensory reorganization theory in chronic pain. To test this in cLBP, we established detailed, fine-grained sensory-topographic maps of the human back in healthy individuals (Cole, 2022; Guekos, 2023) and compared these maps to patients with cLBP by using fMRI during thoracolumbar vibrotactile stimulation. Using this approach, we aimed to test whether the topographic organization observed in healthy controls is altered in patients with cLBP, adding further evidence to support or refute the cortical sensory reorganization theory in chronic pain.
Methods:
41 healthy adults (mean age=29.6 years, SD=5.23; 25 females) and 45 cLBP patients (mean age=30.5 years, SD=8.32; 28 females) were included. fMRI data were collected on a 3T scanner (TR=1.8 s, TE=34 ms, voxel size=1.75×1.7×2 mm3). Participants received bilateral vibrotactile stimuli (20 Hz and 80 Hz) in randomized order at nine segmental levels of the thoracolumbar spine (Cole, 2022). These frequencies were chosen to evaluate the contribution of different mechanoreceptors to cortical activation patterns (Schellekens, 2021). Representational similarity analysis (RSA) with a whole-brain searchlight approach (Kriegeskorte, 2006) was used to examine somatosensory cortical representations of the back, coupled with models to probe the neural organization of stimulation location encoding. A random model served as a control. Brain representational dissimilarity matrices (RDMs) for each pair were computed using Mahalanobis distances and compared to the model RDMs with Kendall's tau correlation. Significant clusters were identified using permutation-based threshold-free cluster enhancement (TFCE, N=10,000).
Results:
A segmental model, reflecting the spatial proximity of adjacent spinal segments in a dermatomal manner, demonstrated the best fit to the neural activation patterns, both in healthy individuals and patients with cLBP. The model fit was significant in both 20 Hz and 80 Hz conditions, revealing informative clusters in the sensorimotor cortices and extending into the superior parietal lobule (SPL). The highest z-scores were located in the medial regions of S1, with clusters surviving multiple comparison corrections (TFCE and FWE-corrected, p<0.05). Importantly, no significant differences in representational structure were observed between patients with cLBP and healthy controls, suggesting that the somatotopic organization of paraspinal segments is preserved in patients with cLBP.
Conclusions:
Our findings further challenge the hypothesis that chronic pain conditions, such as cLBP, are associated with cortical reorganization in the primary somatosensory cortex (S1). In line with recent studies on CRPS, our data suggest that the somatosensory representation of the back remains intact in cLBP patients. This therefore calls into question the role and mechanistic understanding of clinical approaches aiming at restoring somatotopic organization, such as mirror therapy and sensory discrimination training.
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI)
Multivariate Approaches 1
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Cortical Anatomy and Brain Mapping 2
Novel Imaging Acquisition Methods:
BOLD fMRI
Perception, Attention and Motor Behavior:
Perception: Tactile/Somatosensory
Keywords:
Cortex
FUNCTIONAL MRI
Multivariate
Pain
Other - cortical reorganization theory
1|2Indicates the priority used for review
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Please indicate below if your study was a "resting state" or "task-activation” study.
Task-activation
Healthy subjects only or patients (note that patient studies may also involve healthy subjects):
Patients
Was this research conducted in the United States?
No
Were any human subjects research approved by the relevant Institutional Review Board or ethics panel?
NOTE: Any human subjects studies without IRB approval will be automatically rejected.
Yes
Were any animal research approved by the relevant IACUC or other animal research panel?
NOTE: Any animal studies without IACUC approval will be automatically rejected.
Not applicable
Please indicate which methods were used in your research:
Functional MRI
For human MRI, what field strength scanner do you use?
3.0T
Which processing packages did you use for your study?
AFNI
SPM
FSL
Free Surfer
Other, Please list
-
Python rsatoolbox
Provide references using APA citation style.
Brumagne, S. (2019). Neuroplasticity of Sensorimotor Control in Low Back Pain. The Journal of orthopaedic and sports physical therapy, 49(6), 402–414. https://doi.org/10.2519/jospt.2019.8489
Cole, D.M. (2022). In the back of your mind: Cortical mapping of paraspinal afferent inputs. Human brain mapping, 43(16), 4943–4953. https://doi.org/10.1002/hbm.26052
Flor, H. (1997). Extensive reorganization of primary somatosensory cortex in chronic back pain patients. Neuroscience letters, 224(1), 5–8. https://doi.org/10.1016/s0304-3940(97)13441-3
Kriegeskorte, N. (2006). Information-based functional brain mapping. Proceedings of the National Academy of Sciences of the United States of America, 103(10), 3863–3868. https://doi.org/10.1073/pnas.0600244103
Kriegeskorte, N. (2008). Representational similarity analysis - connecting the branches of systems neuroscience. Frontiers in systems neuroscience, 2, 4. https://doi.org/10.3389/neuro.06.004.2008
Guekos, A. (2023). BackWards - Unveiling the brain's topographic organization of paraspinal sensory input. NeuroImage, 283, 120431. https://doi.org/10.1016/j.neuroimage.2023.120431
Mancini, F. (2019). Fine-Grained Mapping of Cortical Somatotopies in Chronic Complex Regional Pain Syndrome. The Journal of neuroscience: the official journal of the Society for Neuroscience, 39(46), 9185–9196. https://doi.org/10.1523/JNEUROSCI.2005-18.2019
Schabrun, S. M., Elgueta-Cancino, E. L., & Hodges, P. W. (2017). Smudging of the Motor Cortex Is Related to the Severity of Low Back Pain. Spine, 42(15), 1172–1178. https://doi.org/10.1097/BRS.0000000000000938
Schellekens, W. (2021). A touch of hierarchy: population receptive fields reveal fingertip integration in Brodmann areas in human primary somatosensory cortex. Brain structure & function, 226(7), 2099–2112. https://doi.org/10.1007/s00429-021-02309-5
Vittersø, A.D. (2022). The sensorimotor theory of pathological pain revisited. Neuroscience and biobehavioral reviews, 139, 104735. https://doi.org/10.1016/j.neubiorev.2022.104735
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