Differences in the organization of the primary motor cortex in people with and without low back pain and associations with motor control and sensory tests.

Differences in organization of the primary motor cortex and altered trunk motor control (sensing, processing and motor output) have been reported in people with low back pain (LBP). Little is known to what extent these differences are related. We investigated differences in 1) organization of the primary motor cortex and 2) motor and sensory tests between people with and without LBP, and 3) investigated associations between the organization of the primary motor cortex and motor and sensory tests. We conducted a case-control study in people with (N=25) and without (N=25) LBP. The organization of the primary motor cortex (Center of Gravity (CoG) and Area of the cortical representation of trunk muscles) was assessed using neuronavigated transcranial magnetic stimulation, based on individual MRIs. Sensory tests (quantitative sensory testing, graphaesthesia, two-point discrimination threshold) and a motor test (spiral-tracking test) were assessed. Participants with LBP had a more lateral and lower location of the CoG and a higher temporal summation of pain. For all participants combined, better vibration test scores were associated with a more anterior, lateral, and lower CoG and a better two-point discrimination threshold was associated with a lower CoG. A small subset of variables showed significance. Although this aligns with the concept of altered organization of the primary motor cortex in LBP, there is no strong evidence of the association between altered organization of the primary motor cortex and motor and sensory test performance in LBP. Focusing on subgroup analyses regarding pain duration can be a topic for future research.

Reliability of two lumbar motor control tests for people with low back pain that are feasible in clinical practice.

BACKGROUND: Clinically feasible and reliable methods to measure motor control in people with low back pain (LBP) are lacking. This reliability and measurement error study design (i.e. repeated measurements in stable patients) aimed to determine the intra- and interrater reliability, and measurement errors of several parameters for two clinical lumbar motor control tests. METHOD: Participants 18-65 years of age, with current or a history of LBP performed a spiral tracking task (n = 33; i.e., tracing a spiral on a computer monitor by making spinal movements) or a repositioning task (n = 34; i.e., returning the trunk to a predefined position). Accelerometers were used to measure trunk positions. To explore the potential of these tests, we evaluated a broad range of parameters. To assess intra- and interrater reliability, we calculated the intraclass correlation coefficient (ICC(2,1) for absolute agreement), standard error of measurement and smallest detectable change for each parameter. FINDINGS: Overall, the interrater reliability of the spiral tracking test was good (ICC>0.75). The reliability of the second and third trial revealed higher ICC values compared to the reliability of the first two trials. The intra- and interrater reliability of the repositioning test was overall poor (ICC <0.5, with the exception of trunk inclination: ICC: 0.5 to 0.75). CONCLUSION: The reliability and set-up of the spiral tracking test supports its feasibility for clinical use. Considering the poor reliability of the repositioning test, it is doubtful whether further development of this measurement protocol is indicated. Only for the direction trunk inclination further standardisation might be warranted.

Associations between primary motor cortex organization, motor control and sensory tests during the clinical course of low back pain. A protocol for a cross-sectional and longitudinal case-control study.

Background: In people with low back pain (LBP), altered motor control has been related to reorganization of the primary motor cortex (M1). Sensory impairments in LBP have also been suggested to be associated with reorganization of M1. Little is known about reorganization of M1 over time in people with LBP, and whether it relates to changes in motor control and sensory impairments and recovery. This study aims to investigate 1) differences in organization of M1 of trunk muscles between people with and without LBP, and whether the organization of M1 relates to motor control and sensory impairments (cross-sectional component) and 2) reorganization of M1 over time and its relation with changes in motor control and sensory impairments and experienced recovery (longitudinal component). Methods: A case-control study with a cross-sectional and five-week longitudinal component is conducted in participants with LBP (N = 25) and participants without LBP (N = 25). Participants with LBP received usual care physiotherapy. Various tests were administered at baseline and follow-up. Following an anatomical MRI, organization of M1 (Center of Gravity and Area of the cortical representation of trunk muscles) was determined using transcranial magnetic stimulation. Quantitative sensory testing, a spiral-tracking motor control test, graphesthesia, two-point discrimination threshold and various self-reported questionnaires were also assessed. Multivariate multilevel analysis will be used for statistical analysis. Conclusion: We will address the gaps in knowledge about the association between reorganization of M1 and motor control and sensory tests during the clinical course of LBP. This study is registered at DOI 10.17605/OSF.IO/5C8ZG.