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Hotz Boendermaker S1, Boendermaker B2,3
1University of Applied Science, Winterthur, Switzerland, 2Departmtent of Physiotherapy, Winterthur, Switzerland, 3VUB, Physiotherapy, Human Physiology & Anatomy, Brussel, Belgium
Background: Low back pain (LBP) is amongst the most prevalent health problems in the working-age population and conventional treatments of structural and functional impairments of the spine were frequently unsuccessful. Growing evidence is suggesting that neurodysfunctional mechanisms are involved in maintaining LBP. To investigate such maladaptive changes, neuroimaging methods can be used to investigate the role of somatosensory processing in chronic LBP (CLBP) and reported changes in the brain's function.
Purpose: The present functional MRI (fMRI) study aimed to reveal central processing of non-painful somatosensory input as well as neuroplastic changes in CLBP patients by using a clinically relevant non-painful stimulus.
Methods: An experienced manual therapist applied force controlled, non-painful posterior-to-anterior (PA) pressure of 30N on spinous processes L1, L3 and L5 in 14 controls and 14 CLBP patients. The randomized stimulation protocol consisted of 51 stimuli of 5 seconds duration and a jittered inter-stimulus interval between 6 to 8 seconds. Data analysis was performed using SPM8. After fixed-effect analysis, the individual contrast images (pressure > rest) were included in a flexible factorial model with the factors group (controls and CLBP patients), level of stimulation (L1, L3 and L5), and considering level × group interaction. This was followed up with two-sample T-tests to examine simple main effects of group. All results were family-wise error corrected (p 0.05).
Results: The application of PA pressure on the lumbar spine resulted in a significant hemodynamic response in somatosensory cortices, anterior cingulate and premotor cortices and in the anterior cerebellum, in the control group. The patient group showed smaller activations mainly in the right hemisphere. The flexible factorial design revealed a main effect for groups in the orbitofrontal cortex. There were no effects found for the level of stimulation and for the interaction effect for group x level of stimulation. The subsequent analysis of the comparison controls > patients revealed activation bilaterally in the orbitofrontal cortices, in the in the left operculo-insular cortex and in the premotor ventral area. The patient group did not reveal enhanced activations compared with the controls.
Conclusion(s): The present study revealed the effect of mechanical stimuli on the lower back to induce significant hemodynamic responses in networks responsible for perception, processing and retaining mechanosensory information. Subsequently, in daily life, this sensory input might provide a basis for body perception, anticipatory postural adjustments and stabilization of the lumbar spine. Unfortunately, this mechanism seems to be impaired in CLBP patients. In particular, prefrontal cortices integrate information from large-scale networks, among others sensory perception, interoceptive signals and internal representations. The goal is to give these processes a sense of significance by adding an affective quality to induce adequate behavioral responses. These results therefore might indicate that the perception of non-painful mechanical stimulation is functional in controls and patients, although the interpretation of meaningfulness is maladaptive in CLBP patients, in particular to affectively evaluate non-painful sensory inputs.
Implications: As treatments based on functional and structural abnormalities of CLBP patients are frequently unsuccessful, these findings support the growing evidence that additional emotional mechanisms are involved in maladaptive somatosensory processing.
Keywords: Low back pain, functional MRI, reorganisation
Funding acknowledgements: Swiss National Science Foundation
Purpose: The present functional MRI (fMRI) study aimed to reveal central processing of non-painful somatosensory input as well as neuroplastic changes in CLBP patients by using a clinically relevant non-painful stimulus.
Methods: An experienced manual therapist applied force controlled, non-painful posterior-to-anterior (PA) pressure of 30N on spinous processes L1, L3 and L5 in 14 controls and 14 CLBP patients. The randomized stimulation protocol consisted of 51 stimuli of 5 seconds duration and a jittered inter-stimulus interval between 6 to 8 seconds. Data analysis was performed using SPM8. After fixed-effect analysis, the individual contrast images (pressure > rest) were included in a flexible factorial model with the factors group (controls and CLBP patients), level of stimulation (L1, L3 and L5), and considering level × group interaction. This was followed up with two-sample T-tests to examine simple main effects of group. All results were family-wise error corrected (p 0.05).
Results: The application of PA pressure on the lumbar spine resulted in a significant hemodynamic response in somatosensory cortices, anterior cingulate and premotor cortices and in the anterior cerebellum, in the control group. The patient group showed smaller activations mainly in the right hemisphere. The flexible factorial design revealed a main effect for groups in the orbitofrontal cortex. There were no effects found for the level of stimulation and for the interaction effect for group x level of stimulation. The subsequent analysis of the comparison controls > patients revealed activation bilaterally in the orbitofrontal cortices, in the in the left operculo-insular cortex and in the premotor ventral area. The patient group did not reveal enhanced activations compared with the controls.
Conclusion(s): The present study revealed the effect of mechanical stimuli on the lower back to induce significant hemodynamic responses in networks responsible for perception, processing and retaining mechanosensory information. Subsequently, in daily life, this sensory input might provide a basis for body perception, anticipatory postural adjustments and stabilization of the lumbar spine. Unfortunately, this mechanism seems to be impaired in CLBP patients. In particular, prefrontal cortices integrate information from large-scale networks, among others sensory perception, interoceptive signals and internal representations. The goal is to give these processes a sense of significance by adding an affective quality to induce adequate behavioral responses. These results therefore might indicate that the perception of non-painful mechanical stimulation is functional in controls and patients, although the interpretation of meaningfulness is maladaptive in CLBP patients, in particular to affectively evaluate non-painful sensory inputs.
Implications: As treatments based on functional and structural abnormalities of CLBP patients are frequently unsuccessful, these findings support the growing evidence that additional emotional mechanisms are involved in maladaptive somatosensory processing.
Keywords: Low back pain, functional MRI, reorganisation
Funding acknowledgements: Swiss National Science Foundation
Topic: Musculoskeletal; Human movement analysis; Pain & pain management
Ethics approval required: Yes
Institution: University of Applied Science
Ethics committee: Canton of Zurich
Ethics number: 2016-02096
All authors, affiliations and abstracts have been published as submitted.
