Hotz-Boendermaker S.1, Boendermaker B.1, Meier M.L.2, Humphreys B.K.2
1Zurich University of Applied Sciences, Institute of Physiotherapy, Winterthur, Switzerland, 2University Hospital Balgrist, Chiropractic Medicine, Zurich, Switzerland
Background: Non-painful posterior-to-anterior (PA) lumbar pressure has revealed an extensive network of brain activation in regions previously described for attention, proprioceptive memory retention and anticipatory postural control that may act as a proxy for actual lumbar movement1.
Purpose: The present functional magnetic resonance imaging (fMRI) study aimed to investigate cortical somatosensory processing of this non-painful clinically relevant stimulus in chronic low back pain (CLBP) patients.
Methods: Force controlled, non-painful PA pressure of 30N was directed on spinous processes of 16 controls and 14 CLBP patients. Fifty-one stimuli (duration 5s) were randomly applied at three lumbar levels (L1,L3,L5). Data analysis was performed using SPM8. Differences between CLBP patients and controls were computed for the primary somatosensory cortex (S1) for 1) activation representing average level of brain activity as response to the PA stimulation and 2) functional connectivity (FC) to reveal additional information about the degree by which components of the large-scale sensorimotor systems are functionally coupled together to process sensory input. FC was computed using the seed region right S1 derived from group peak activations.
Results: Average activation within S1 did not reveal differences between CLBP patients and controls in the whole head analysis. Reorganization was demonstrated in the FC analyses in the CLBP group compared to the control group. Reduced FC was found between the seed region right S1 and right premotor areas (supplementary motor area SMA; premotor dorsal) and bilateral prefrontal cortex. Enhanced FC was detected between right S1 and secondary somatosensory Cortex (S2) and parietal cortex in the left hemisphere.
Conclusion(s): The findings demonstrated maladaptive changes in sensory information processing of the lower back in CLBP patients that may provide an indication of the mechanism by which persistent pain leads to functional disability. First, the reduced interaction between S1 and Areas, responsible for the preparation and control of behavior, may reflect trunk movement coordination impairments in CLBP. In particular, as the premotor region SMA has been repeatedly reported to be involved in postural control. Furthermore, somatosensory-parietal circuits provide an internal body representation which is subsequently mapped onto corresponding premotor regions and used for movement preparation, tactile acuity and lumbar proprioceptive awareness. Stronger interaction within this network in the patient group may indicate enhanced information processing due to impaired integration of multisensory information of the body in persistent LBP. We hypothesize that in a pain state, painful input draws full attention and may lead to a down-regulation of non-painful sensory input that result in reorganization of sensory processing.
Implications: Fortunately, maladaptive reorganization is reversible. Therefore, research is needed to determine if sensorimotor therapies is beneficial in activation of the mechanosensory cortices and results in the restoration of normal sensorimotor activity of the lower back.
1 The cortical and cerebellar representation of the lumbar spine. Boendermaker B, Meier ML, Luechinger R, Humphreys BK, Hotz-Boendermaker S.Hum Brain Mapp. 2014 Aug;35(8):3962-71.
Funding acknowledgements: No funding acknowledgements
Topic: Pain & pain management
Ethics approval: This study was approved by the Ethics Committee of the Canton of Zurich, Switzerland.
All authors, affiliations and abstracts have been published as submitted.
