Microstructural integrity of the superior cerebellar peduncle is associated with an impaired proprioceptive weighting capacity in individuals with non-specific low back pain

Organization of sensorimotor activity in anterior cruciate ligament reconstructed individuals: an fMRI conjunction analysis

Introduction

Anterior cruciate ligament reconstruction (ACLR) is characterized by persistent involved limb functional deficits that persist for years despite rehabilitation. Previous research provides evidence of both peripheral and central nervous system adaptations following ACLR. However, no study has compared functional organization of the brain for involved limb motor control relative to the uninvolved limb and healthy controls. The purpose of this study was to examine sensorimotor cortex and cerebellar functional activity overlap and non-overlap during a knee motor control task between groups (ACLR and control), and to determine cortical organization of involved and uninvolved limb movement between groups.

Methods

Eighteen participants with left knee ACLR and 18 control participants performed a knee flexion/extension motor control task during functional magnetic resonance imaging (fMRI). A conjunction analysis was conducted to determine the degree of overlap in brain activity for involved and uninvolved limb knee motor control between groups.

Results

The ACLR group had a statistically higher mean percent signal change in the sensorimotor cortex for the involved > uninvolved contrast compared to the control group. Brain activity between groups statistically overlapped in sensorimotor regions of the cortex and cerebellum for both group contrasts: involved > uninvolved and uninvolved > involved. Relative to the control group, the ACLR group uniquely activated superior parietal regions (precuneus, lateral occipital cortex) for involved limb motor control. Additionally, for involved limb motor control, the ACLR group displayed a medial and superior shift in peak voxel location in frontal regions; for parietal regions, the ACLR group had a more posterior and superior peak voxel location relative to the control group.

Conclusion

ACLR may result in unique activation of the sensorimotor cortex via a cortically driven sensory integration strategy to maintain involved limb motor control. The ACLR group's unique brain activity was independent of strength, self-reported knee function, and time from surgery.

The Role of Back Muscle Dysfunctions in Chronic Low Back Pain: State-of-the-Art and Clinical Implications

Changes in back muscle function and structure are highly prevalent in patients with chronic low back pain (CLBP). Since large heterogeneity in clinical presentation and back muscle dysfunctions exists within this population, the potential role of back muscle dysfunctions in the persistence of low back pain differs between individuals. Consequently, interventions should be tailored to the individual patient and be based on a thorough clinical examination taking into account the multidimensional nature of CLBP. Considering the complexity of this process, we will provide a state-of-the-art update on back muscle dysfunctions in patients with CLBP and their implications for treatment. To this end, we will first give an overview of (1) dysfunctions in back muscle structure and function, (2) the potential of exercise therapy to address these dysfunctions, and (3) the relationship between changes in back muscle dysfunctions and clinical parameters. In a second part, we will describe a framework for an individualised approach for back muscle training in patients with CLBP.

Nociceptive withdrawal reflexes of the trunk muscles in chronic low back pain

Individuals with chronic low back pain (CLBP) move their spine differently. Changes in brain motor areas have been observed and suggested as a mechanism underlying spine movement alteration. Nociceptive withdrawal reflex (NWR) might be used to test spinal networks involved in trunk protection and to highlight reorganization. This study aimed to determine whether the organization and excitability of the trunk NWR are modified in CLBP. We hypothesized that individuals with CLBP would have modified NWR patterns and lower NWR thresholds. Noxious electrical stimuli were delivered over S1, L3 and T12, and the 8th Rib to elicit NWR in 12 individuals with and 13 individuals without CLBP. EMG amplitude and occurrence of lumbar multifidus (LM), thoracic erector spinae, rectus abdominus, obliquus internus and obliquus externus motor responses were recorded using surface electrodes. Two different patterns of responses to noxious stimuli were identified in CLBP compared to controls: (i) abdominal muscle NWR responses were generally more frequent following 8th rib stimulation and (ii) occurrence of erector spinae NWR was less frequent. In addition, we observed a subgroup of participants with very high NWR threshold in conjunction with the larger abdominal muscle responses. These results suggest sensitization of NWR is not present in all individuals with CLBP, and a modified organization in the spinal networks controlling the trunk muscles that might explain some changes in spine motor control observed in CLBP.

The effects of proprioceptive weighting changes on posture control in patients with chronic low back pain: a cross-sectional study

Introduction

Patients with chronic low back pain (CLBP) exhibit changes in proprioceptive weighting and impaired postural control. This study aimed to investigate proprioceptive weighting changes in patients with CLBP and their influence on posture control.

Methods

Sixteen patients with CLBP and 16 healthy controls were recruited. All participants completed the joint reposition test sense (JRS) and threshold to detect passive motion test (TTDPM). The absolute errors (AE) of the reposition and perception angles were recorded. Proprioceptive postural control was tested by applying vibrations to the triceps surae or lumbar paravertebral muscles while standing on a stable or unstable force plate. Sway length and sway velocity along the anteroposterior (AP) and mediolateral (ML) directions were assessed. Relative proprioceptive weighting (RPW) was used to evaluate the proprioception reweighting ability. Higher values indicated increased reliance on calf proprioception.

Results

There was no significant difference in age, gender, and BMI between subjects with and without CLBP. The AE and motion perception angle in the CLBP group were significantly higher than those in the control group (JRS of 15°: 2.50 (2.50) vs. 1.50 (1.42), JRS of 35°: 3.83 (3.75) vs. 1.67 (2.00), p_JRS < 0.01; 1.92 (1.18) vs. 0.68 (0.52), p_TTDPM < 0.001). The CLBP group demonstrated a significantly higher RPW value than the healthy controls on an unstable surface (0.58 ± 0.21 vs. 0.41 ± 0.26, p < 0.05). Under the condition of triceps surae vibration, the sway length (p_stable < 0.05; p_unstable < 0.001), AP velocity (p_stable < 0.01; p_unstable < 0.001) and ML velocity (p_unstable < 0.05) had significant group main effects. Moreover, when the triceps surae vibrated under the unstable surface, the differences during vibration and post vibration in sway length and AP velocity between the groups were significantly higher in the CLBP group than in the healthy group (p < 0.05). However, under the condition of lumbar paravertebral muscle vibration, no significant group main effect was observed.

Conclusion

The patients with CLBP exhibited impaired dynamic postural control in response to disturbances, potentially linked to changes in proprioceptive weighting.

Causal relationships between migraine and microstructural white matter: a Mendelian randomization study

BACKGROUND

Migraine is a disabling neurological disorder with the pathophysiology yet to be understood. The microstructural alteration in brain white matter (WM) has been suggested to be related to migraine in recent studies, but these evidence are observational essentially and cannot infer a causal relationship. The present study aims to reveal the causal relationship between migraine and microstructural WM using genetic data and Mendelian randomization (MR).

METHODS

We collected the Genome-wide association study (GWAS) summary statistics of migraine (48,975 cases / 550,381 controls) and 360 WM imaging-derived phenotypes (IDPs) (31,356 samples) that were used to measure microstructural WM. Based on instrumental variables (IVs) selected from the GWAS summary statistics, we conducted bidirectional two-sample MR analyses to infer bidirectional causal associations between migraine and microstructural WM. In forward MR analysis, we inferred the causal effect of microstructural WM on migraine by reporting the odds ratio (OR) that quantified the risk change of migraine for per 1 standard deviation (SD) increase of IDPs. In reverse MR analysis, we inferred the causal effect of migraine on microstructural WM by reporting the β value that represented SDs of changes in IDPs were caused by migraine.

RESULTS

Three WM IDPs showed significant causal associations (p < 3.29 × 10- 4, Bonferroni correction) with migraine and were proved to be reliable via sensitivity analysis. The mode of anisotropy (MO) of left inferior fronto-occipital fasciculus (OR = 1.76, p = 6.46 × 10- 5) and orientation dispersion index (OD) of right posterior thalamic radiation (OR = 0.78, p = 1.86 × 10- 4) exerted significant causal effects on migraine. Migraine exerted a significant causal effect on the OD of left superior cerebellar peduncle (β = - 0.09, p = 2.78 × 10- 4).

CONCLUSIONS

Our findings provided genetic evidence for the causal relationships between migraine and microstructural WM, bringing new insights into brain structure for the development and experience of migraine.

Amplitude of Electromyographic Activity of Trunk and Lower Extremity Muscles during Oscillatory Forces of Flexi-Bar on Stable and Unstable Surfaces in People with Nonspecific Low Back Pain

BACKGROUND

Recently, the oscillatory bar has been proposed as a new and effective rehabilitation tool in people with nonspecific low back pain (NSLBP), although its effects on muscular control in this population have not been well documented, especially in lower extremity muscles and different support surface conditions.

OBJECTIVE

This study aimed to evaluate and compare the effects of flexi-bar use on stable and unstable surfaces on electromyographic activity of trunk and lower extremity muscles in healthy persons and those with NSLBP.

MATERIAL AND METHODS

18 healthy men and 18 men with NSLBP participated in this cross-sectional study. The root mean square value of electromyographic activity was calculated in the trunk and lower extremity muscles during 4 different task conditions: quiet standing (QS) or flexi-bar use on a rigid or foam support surface. A repeated measures test was used for statistical analysis.

RESULTS

The results showed that the amplitude activity of almost all muscles was significantly greater during flexi-bar use than in the QS condition (P<0.05). The rectus femoris, tibialis anterior, and gastrocnemius demands were significantly greater on the foam than the rigid surface (P<0.05).

CONCLUSION

This study showed that oscillatory forces caused by flexi-bar use can increase muscle activation in multiple segments (hip and ankle in addition to trunk muscles) that are crucial for postural stability. Furthermore, the foam surface appeared to target the rectus femoris in addition to the ankle muscles. Using a flexi-bar may be helpful in NSLBP rehabilitation, and exercising on a foam surface may enhance additive hip muscle activity in people with NSLBP.

People with chronic low back pain display spatial alterations in high-density surface EMG-torque oscillations

We quantified the relationship between spatial oscillations in surface electromyographic (sEMG) activity and trunk-extension torque in individuals with and without chronic low back pain (CLBP), during two submaximal isometric lumbar extension tasks at 20% and 50% of their maximal voluntary torque. High-density sEMG (HDsEMG) signals were recorded from the lumbar erector spinae (ES) with a 64-electrode grid, and torque signals were recorded with an isokinetic dynamometer. Coherence and cross-correlation analyses were applied between the filtered interference HDsEMG and torque signals for each submaximal contraction. Principal component analysis was used to reduce dimensionality of HDsEMG data and improve the HDsEMG-based torque estimation. sEMG-torque coherence was quantified in the δ(0–5 Hz) frequency bandwidth. Regional differences in sEMG-torque coherence were also evaluated by creating topographical coherence maps. sEMG-torque coherence in the δ band and sEMG-torque cross-correlation increased with the increase in torque in the controls but not in the CLBP group (p = 0.018, p = 0.030 respectively). As torque increased, the CLBP group increased sEMG-torque coherence in more cranial ES regions, while the opposite was observed for the controls (p = 0.043). Individuals with CLBP show reductions in sEMG-torque relationships possibly due to the use of compensatory strategies and regional adjustments of ES-sEMG oscillatory activity.

Brainstem Diffusion Tensor Tractography and Clinical Applications in Pain

The brainstem is one of the most vulnerable brain structures in many neurological conditions, such as pain, sleep problems, autonomic dysfunctions, and neurodegenerative disorders. Diffusion tensor imaging and tractography provide structural details and quantitative measures of brainstem fiber pathways. Until recently, diffusion tensor tractographic studies have mainly focused on whole-brain MRI acquisition. Due to the brainstem's spatial localization, size, and tissue characteristics, and limits of imaging techniques, brainstem diffusion MRI poses particular challenges in tractography. We provide a brief overview on recent advances in diffusion tensor tractography in revealing human pathways connecting the brainstem to the subcortical regions (e.g., basal ganglia, mesolimbic, basal forebrain), and cortical regions. Each of these pathways contains different distributions of fiber tracts from known neurotransmitter-specific nuclei in the brainstem. We compare the brainstem tractographic approaches in literature and our in-lab developed automated brainstem tractography in terms of atlas building, technical advantages, and neuroanatomical implications on neurotransmitter systems. Lastly, we summarize recent investigations of using brainstem tractography as a promising tool in association with pain.

The Function Assessment Scale for Spinal Deformity: Validity and Reliability of a New Clinical Scale

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

The aim of this study was to develop and validate the Function Assessment scale for Spinal Deformity (FASD).

SUMMARY OF BACKGROUND DATA

Spinal malalignment impacts daily functioning. Standard evaluation of adult spinal deformity (ASD) is based on static radiography and patient-reported scores, which fail to assess functional impairments. A clinical scale, quantifying function and balance of patients with ASD, could increase our insights on the impact of ASD on functioning.

METHODS

To develop the FASD, 70 ASD patients and 20 controls were measured to identify the most discriminating items of the Balance Evaluation Systems Test and Trunk Control Measurement Scale. Discussions between experts on the clinical relevance of selected items led to further item reduction. The FASD's discriminative ability was established between 43 patients and 19 controls, as well as between three deformity subgroups. For its responsiveness to treatment, 10 patients were reevaluated 6 months postoperatively. Concurrent validity was assessed through correlation analysis with radiographic parameters (pelvic tilt; sagittal vertical axis [SVA]; pelvic incidence minus lumbar lordosis [PI-LL]; coronal vertical axis) and patient-reported scores [Oswestry Disability Index]; Scoliosis Research Society outcome questionnaire; Falls Efficacy Scale-International). Test-retest and interrater reliability were tested on two groups of ten patients using intraclass correlation coefficients (ICC).

RESULTS

Patients with ASD, mainly with sagittal malalignment, scored worse compared to controls on FASD (P < 0.001) and its subscales. No significant improvement was observed 6 months postoperatively (P = 0.758). FASD correlated significantly to all patient-reported scores and to SVA and PI-LL. Reliability between sessions (ICC = 0.97) and raters (ICC = 0.93) was excellent. Subscales also showed good to excellent reliability, except FASD 1 on "spinal mobility and balance" between sessions (ICC = 0.71).

CONCLUSION

FASD proved to be a valid and reliable clinical scale for evaluation of functional impairments in ASD. Objective information on function and balance might ultimately guide physiotherapeutic treatment toward improved functioning.Level of Evidence: 2.

Mechanisms of Arthrogenic Muscle Inhibition

CONTEXT

Arthrogenic muscle inhibition (AMI) continues to be a limiting factor in joint rehabilitation as the inability to volitionally activate muscle significantly dampens recovery. New evidence acquired at higher brain centers and in clinical populations continues to reshape our perspective of what AMI is and how to treat it. This review aims to stimulate discussion about the far-reaching effects of AMI by exploring the interconnected pathways by which it evolves.

OBJECTIVES

To discuss how reflexive inhibition can lead to adaptations in brain activity, to illustrate how changes in descending motor pathways limit our ability to contract muscle following injury, and to summarize the emerging literature on the wide-reaching effects of AMI on other interconnected systems.

DATA SOURCES

The databases PubMed, SPORTDiscus, and Web of Science were searched for articles pertaining to AMI. Reference lists from appropriate articles were cross-referenced.

CONCLUSION

AMI is a sequential and cumulative neurological process that leads to complex clinical impairments. Originating with altered afferent information arising from an injured joint, patients experience changes in afferent information, reflexive muscle inhibition, deficiencies in somatosensation, neuroplastic compensations in higher brain centers, and ultimately decreased motor output to the muscle surrounding the joint. Other aspects of clinical function, like muscle structure and psychological responses to injury, are also impaired and influenced by AMI. Removing, or reducing, AMI should continue to be a focus of rehabilitation programs to assist in the optimization of health after joint injury.

Neurobiological and behavioural outcomes of biofeedback-based training in autism: a randomized controlled trial

The human brain has demonstrated the power to structurally change as a result of movement-based interventions. However, it is unclear whether these structural brain changes differ in autistic individuals compared to non-autistic individuals. The purpose of the present study was to pilot a randomized controlled trial to investigate brain, balance, autism symptom severity and daily living skill changes that result from a biofeedback-based balance intervention in autistic adolescents (13-17 years old). Thirty-four autistic participants and 28 age-matched non-autistic participants underwent diagnostic testing and pre-training assessment (neuroimaging, cognitive, autism symptom severity and motor assessments) and were then randomly assigned to 6 weeks of a balance-training intervention or a sedentary-control condition. After the 6 weeks, neuroimaging, symptom severity and motor assessments were repeated. Results found that both the autistic and non-autistic participants demonstrated similar and significant increases in balance times with training. Furthermore, individuals in the balance-training condition showed significantly greater improvements in postural sway and reductions in autism symptom severity compared to individuals in the control condition. Daily living scores did not change with training, nor did we observe hypothesized changes to the microstructural properties of the corticospinal tract. However, follow-up voxel-based analyses found a wide range of balance-related structures that showed changes across the brain. Many of these brain changes were specific to the autistic participants compared to the non-autistic participants, suggesting distinct structural neuroplasticity in response to balance training in autistic participants. Altogether, these findings suggest that biofeedback-based balance training may target postural stability challenges, reduce core autism symptoms and influence neurobiological change. Future research is encouraged to examine the superior cerebellar peduncle in response to balance training and symptom severity changes in autistic individuals, as the current study produced overlapping findings in this brain region.

Differences in brain structure and theta burst stimulation-induced plasticity implicate the corticomotor system in loss of function after musculoskeletal injury

Traumatic musculoskeletal injury (MSI) may involve changes in corticomotor structure and function, but direct evidence is needed. To determine the corticomotor basis of MSI, we examined interactions among skeletomotor function, corticospinal excitability, corticomotor structure (cortical thickness and white matter microstructure), and intermittent theta burst stimulation (iTBS)-induced plasticity. Nine women with unilateral anterior cruciate ligament rupture (ACL) 3.2 ± 1.1 yr prior to the study and 11 matched controls (CON) completed an MRI session followed by an offline plasticity-probing protocol using a randomized, sham-controlled, double-blind, cross-over study design. iTBS was applied to the injured (ACL) or nondominant (CON) motor cortex leg representation (M1_LEG) with plasticity assessed based on changes in skeletomotor function and corticospinal excitability compared with sham iTBS. The results showed persistent loss of function in the injured quadriceps, compensatory adaptations in the uninjured quadriceps and both hamstrings, and injury-specific increases in corticospinal excitability. Injury was associated with lateralized reductions in paracentral lobule thickness, greater centrality of nonleg corticomotor regions, and increased primary somatosensory cortex leg area inefficiency and eccentricity. Individual responses to iTBS were consistent with the principles of homeostatic metaplasticity; corresponded to injury-related differences in skeletomotor function, corticospinal excitability, and corticomotor structure; and suggested that corticomotor adaptations involve both hemispheres. Moreover, iTBS normalized skeletomotor function and corticospinal excitability in ACL. The results of this investigation directly confirm corticomotor involvement in chronic loss of function after traumatic MSI, emphasize the sensitivity of the corticomotor system to skeletomotor events and behaviors, and raise the possibility that brain-targeted therapies could improve recovery.NEW & NOTEWORTHY Traumatic musculoskeletal injuries may involve adaptive changes in the brain that contribute to loss of function. Our combination of neuroimaging and theta burst transcranial magnetic stimulation (iTBS) revealed distinct patterns of iTBS-induced plasticity that normalized differences in muscle and brain function evident years after unilateral knee ligament rupture. Individual responses to iTBS corresponded to injury-specific differences in brain structure and physiological activity, depended on skeletomotor deficit severity, and suggested that corticomotor adaptations involve both hemispheres.

Accelerated brain aging in chronic low back pain

Chronic low back pain (CLBP) is a leading cause of disability and is associated with neurodegenerative changes in brain structure. These changes lead to impairments in cognitive function and are consistent with those seen in aging, suggesting an accelerated aging pattern. In this study we assessed this using machine-learning estimated brain age (BA) as a holistic metric of morphometric changes associated with aging. Structural imaging data from 31 non-depressed CLBP patients and 32 healthy controls from the Pain and Interoception Imaging Network were included. Using our previously developed algorithm, we estimated BA per individual based on grey matter density. We then conducted multivariable linear modeling for effects of group, chronological age, and their interaction on BA. We also performed two voxel-wise analyses comparing grey matter density between CLBP and control individuals and the association between gray matter density and BA. There was an interaction between CLBP and greater chronological age on BA such that the discrepancy in BA between healthy and CLBP individuals was greater for older individuals. In CLBP individuals, BA was not associated with sex, current level of pain, duration of CLBP, or mild to moderate depressive symptoms. CLBP individuals had lower cerebellar grey matter density compared to healthy individuals. Brain age was associated with lower gray matter density in numerous brain regions. CLBP was associated with greater BA, which was more profound in later life. BA as a holistic metric was sensitive to differences in gray matter density in numerous regions which eluded direct comparison between groups.

Changes in the Organization of the Secondary Somatosensory Cortex While Processing Lumbar Proprioception and the Relationship With Sensorimotor Control in Low Back Pain

OBJECTIVES

Patients with nonspecific low back pain (NSLBP) rely more on the ankle compared with the lower back proprioception while standing, perform sit-to-stand-to-sit (STSTS) movements slower, and exhibit perceptual impairments at the lower back. However, no studies investigated whether these sensorimotor impairments relate to a reorganization of the primary and secondary somatosensory cortices (S1 and S2) and primary motor cortex (M1) during proprioceptive processing.

MATERIALS AND METHODS

Proprioceptive stimuli were applied at the lower back and ankle muscles during functional magnetic resonance imaging in 15 patients with NSLBP and 13 controls. The location of the activation peaks during the processing of proprioception within S1, S2, and M1 were determined and compared between groups. Proprioceptive use during postural control was evaluated, the duration to perform 5 STSTS movements was recorded, and participants completed the Fremantle Back Awareness Questionnaire (FreBAQ) to assess back-specific body perception.

RESULTS

The activation peak during the processing of lower back proprioception in the right S2 was shifted laterally in the NSLBP group compared with the healthy group (P=0.007). Moreover, patients with NSLSP performed STSTS movements slower (P=0.018), and reported more perceptual impairments at the lower back (P<0.001). Finally, a significant correlation between a more lateral location of the activation peak during back proprioceptive processing and a more disturbed body perception was found across the total group (ρ=0.42, P=0.025).

CONCLUSIONS

The results suggest that patients with NSLBP show a reorganization of the higher-order processing of lower back proprioception, which could negatively affect spinal control and body perception.

Corticospinal tract structure and excitability in patients with anterior cruciate ligament reconstruction: A DTI and TMS study

BACKGROUND

Underlying neural factors contribute to poor outcomes following anterior cruciate ligament reconstruction (ACLR). Neurophysiological adaptations have been identified in corticospinal tract excitability, however limited evidence exists on neurostructural changes that may influence motor recovery in ACLR patients.

OBJECTIVE

To 1) quantify hemispheric differences in structural properties of the corticospinal tract in patients with a history of ACLR, and 2) assess the relationship between excitability and corticospinal tract structure.

METHODS

Ten participants with ACLR (age: 22.6 ± 1.9 yrs; height: 166.3 ± 7.5 cm; mass: 65.4 ± 12.6 kg, months from surgery: 70.0 ± 23.6) volunteered for this cross-sectional study. Corticospinal tract structure (volume; fractional anisotropy [FA]; axial diffusivity [AD]; radial diffusivity [RD]; mean diffusivity [MD]) was assessed using diffusion tensor imaging, and excitability was assessed using transcranial magnetic stimulation (motor evoked potentials normalized to maximal muscle response [MEP]) for each hemisphere. Hemispheric differences were evaluated using paired samples t-tests. Correlational analyses were conducted on structural and excitability outcomes.

RESULTS

The hemisphere of the ACLR injured limb (i.e. hemisphere contralateral to the ACLR injured limb) demonstrated lower volume, lower FA, higher MD, and smaller MEPs compared to the hemisphere of the non-injured limb, indicating disrupted white matter structure and a reduction in excitability of the corticospinal tract. Greater corticospinal tract excitability was associated with larger corticospinal tract volume.

CONCLUSIONS

ACLR patients demonstrated asymmetry in structural properties of the corticospinal tract that may influence the recovery of motor function following surgical reconstruction. More research is warranted to establish the influence of neurostructural measures on patient outcomes and response to treatment in ACLR populations.

Neuromuscular exercise reduces low back pain intensity and improves physical functioning in nursing duties among female healthcare workers; secondary analysis of a randomised controlled trial

Background

Low back pain (LBP) is common among healthcare workers, whose work is physically strenuous and thus demands certain levels of physical fitness and spinal control. Exercise is the most frequently recommended treatment for LBP. However, exercise interventions targeted at sub-acute or recurrent patients are scarce compared to those targeted at chronic LBP patients. Our objective was to examine the effects of 6 months of neuromuscular exercise on pain, lumbar movement control, fitness, and work-related factors at 6- and 12-months’ follow-up among female healthcare personnel with sub-acute or recurrent low back pain (LBP) and physically demanding work.

Methods

A total of 219 healthcare workers aged 30–55 years with non-specific LBP were originally allocated to four groups (exercise, counselling, combined exercise and counselling, control). The present study is a secondary analysis comparing exercisers (n = 110) vs non-exercisers (n = 109). Exercise was performed twice a week (60 min) in three progressive stages focusing on controlling the neutral spine posture. The primary outcome was intensity of LBP. Secondary outcomes included pain interfering with work, lumbar movement control, fitness components, and work-related measurements. Between-group differences were analysed with a generalised linear mixed model according to the intention-to-treat principle. Per-protocol analysis compared the more exercised to the less exercised and non-exercisers.

Results

The mean exercise attendance was 26.3 (SD 12.2) of targeted 48 sessions over 24 weeks, 53% exercising 1–2 times a week, with 80% (n = 176) and 72% (n = 157) participating in 6- and in 12-month follow-up measurements, respectively. The exercise intervention reduced pain (p = 0.047), and pain interfering with work (p = 0.046); improved lumbar movement control (p = 0.042), abdominal strength (p = 0.033) and physical functioning in heavy nursing duties (p = 0.007); but had no effect on other fitness and work-related measurements when compared to not exercising. High exercise compliance resulted in less pain and better lumbar movement control and walking test results.

Conclusion

Neuromuscular exercise was effective in reducing pain and improving lumbar movement control, abdominal strength, and physical functioning in nursing duties compared to not exercising.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2678-x) contains supplementary material, which is available to authorized users.

Neuroplasticity of Sensorimotor Control in Low Back Pain

Low back pain (LBP) is an important medical and socioeconomic problem. Impaired sensorimotor control has been suggested to be a likely mechanism underlying development and/or maintenance of pain. Although early work focused on the structural and functional abnormalities within the musculoskeletal system, in the past 20 years there has been an increasing realization that patients with LBP might also have extensive neuroplastic changes within the central nervous system. These include changes related to both the structure (eg, gray matter changes) and function (eg, organization of the sensory and motor cortices) of the nervous system as related to processing of pain and nociception and to motor and somatosensory systems. Moreover, clinical interventions increasingly aim to drive neuroplasticity with treatments to improve pain and sensorimotor function. This commentary provides a contemporary overview of neuroplasticity of the pain/nociceptive and sensorimotor systems in LBP. This paper addresses (1) defining neuroplasticity in relation to control of the spine and LBP, (2) structural and functional nervous system changes as they relate to nonspecific LBP and sensorimotor function, and (3) related clinical implications. Individuals with recurrent and persistent LBP differ from those without LBP in several markers of the nervous system's function and structure. Neuroplastic changes may be addressed by top-down cognitive-based interventions and bottom-up physical interventions. An integrated clinical approach that combines contemporary pain neuroscience education, cognition-targeted sensorimotor control, and physical or function-based treatments may lead to better outcomes in patients with recurrent and persistent LBP. This approach will need to consider variation among individuals, as no single finding/mechanism is present in all individuals, and no single treatment that targets neuroplastic changes in the sensorimotor system is likely to be effective for all patients with LBP. J Orthop Sports Phys Ther 2019;49(6):402-414. doi:10.2519/jospt.2019.8489.

Differences in brain processing of proprioception related to postural control in patients with recurrent non-specific low back pain and healthy controls

Patients with non-specific low back pain (NSLBP) show an impaired postural control during standing and a slower performance of sit-to-stand-to-sit (STSTS) movements. Research suggests that these impairments could be due to an altered use of ankle compared to back proprioception. However, the neural correlates of these postural control impairments in NSLBP remain unclear. Therefore, we investigated brain activity during ankle and back proprioceptive processing by applying local muscle vibration during functional magnetic resonance imaging in 20 patients with NSLBP and 20 controls. Correlations between brain activity during proprioceptive processing and (Airaksinen et al., 2006) proprioceptive use during postural control, evaluated by using muscle vibration tasks during standing, and (Altmann et al., 2007) STSTS performance were examined across and between groups. Moreover, fear of movement was assessed. Results revealed that the NSLBP group performed worse on the STSTS task, and reported more fear compared to healthy controls. Unexpectedly, no group differences in proprioceptive use during postural control were found. However, the relationship between brain activity during proprioceptive processing and behavioral indices of proprioceptive use differed significantly between NSLBP and healthy control groups. Activity in the right amygdala during ankle proprioceptive processing correlated with an impaired proprioceptive use in the patients with NSLBP, but not in healthy controls. Moreover, while activity in the left superior parietal lobule, a sensory processing region, during back proprioceptive processing correlated with a better use of proprioception in the NSLBP group, it was associated with a less optimal use of proprioception in the control group. These findings suggest that functional brain changes during proprioceptive processing in patients with NSLBP may contribute to their postural control impairments.

The development of the Dutch version of the Fremantle Back Awareness Questionnaire

BACKGROUND

Disturbed body perception may play a role in the aetiology of chronic low back pain (LBP). The Fremantle Back Awareness Questionnaire (FreBAQ) is currently the only self-report questionnaire to assess back-specific body perception in individuals with LBP.

OBJECTIVES

To perform a cross-cultural adaptation of the FreBAQ into Dutch.

DESIGN

Psychometric study.

METHODS

A Dutch version of the FreBAQ was generated through forward-backward translation, and was completed by 73 patients with LBP and 73 controls to assess discriminant validity. Structural validity was assessed by principal component analysis. Internal consistency was assessed by the Cronbach's alpha coefficient. Construct validity was assessed by examining the relationship with clinical measures (Numerical Rating Scale pain, Oswestry Disability Index (ODI), Tampa Scale for Kinesiophobia). Test-retest reliability was assessed in a subgroup (n = 48 with LBP and 48 controls) using intraclass correlation coefficients (ICC), standard error of measurement (SEM) and minimal detectable change (MDC 95%) RESULTS: The Dutch FreBAQ showed one component with eigenvalue >2. Cronbach's alpha values were respectively 0.82 and 0.73 for the LBP and control group. ICC values were respectively 0.69 and 0.70 for the LBP and control group. In the LBP group, the SEM was 3.9 and the MDC (95%) was 10.8. The LBP group (ODI 22 ± 21%) scored significantly higher on the Dutch FreBAQ than the control group (ODI 0%) (11 ± 7 vs. 3 ± 9, p < 0.001). Within the LBP group, higher Dutch FreBAQ scores correlated significantly with higher ODI scores (rho = 0.30, p = 0.010), although not with pain (rho = 0.10, p = 0.419) or kinesiophobia (r = 0.14, p = 0.226).

CONCLUSIONS

The Dutch version of the FreBAQ can be considered as unidimensional and showed adequate internal consistency, sufficient test-retest reliability and adequate discriminant and construct validity in individuals with and without LBP. It can improve our understanding on back-specific perception in the Dutch-speaking population with LBP.

Anodal Transcranial Direct Current Stimulation Shows Minimal, Measure-Specific Effects on Dynamic Postural Control in Young and Older Adults: A Double Blind, Sham-Controlled Study

We investigated whether stimulating the cerebellum and primary motor cortex (M1) using transcranial direct current stimulation (tDCS) could affect postural control in young and older adults. tDCS was employed using a double-blind, sham-controlled design, in which young (aged 18–35) and older adults (aged 65+) were assessed over three sessions, one for each stimulatory condition–M1, cerebellar and sham. The effect of tDCS on postural control was assessed using a sway-referencing paradigm, which induced platform rotations in proportion to the participant’s body sway, thus assessing sensory reweighting processes. Task difficulty was manipulated so that young adults experienced a support surface that was twice as compliant as that of older adults, in order to minimise baseline age differences in postural sway. Effects of tDCS on postural control were assessed during, immediately after and 30 minutes after tDCS. Additionally, the effect of tDCS on corticospinal excitability was measured by evaluating motor evoked potentials using transcranial magnetic stimulation immediately after and 30 minutes after tDCS. Minimal effects of tDCS on postural control were found in the eyes open condition only, and this was dependent on the measure assessed and age group. For young adults, stimulation had only offline effects, as cerebellar stimulation showed higher mean power frequency (MPF) of sway 30 minutes after stimulation. For older adults, both stimulation conditions delayed the increase in sway amplitude witnessed between blocks one and two until stimulation was no longer active. In conclusion, despite tDCS’ growing popularity, we would caution researchers to consider carefully the type of measures assessed and the groups targeted in tDCS studies of postural control.

Associations between Measures of Structural Morphometry and Sensorimotor Performance in Individuals with Nonspecific Low Back Pain

BACKGROUND AND PURPOSE

To date, most structural brain imaging studies in individuals with nonspecific low back pain have evaluated volumetric changes. These alterations are particularly found in sensorimotor-related areas. Although it is suggested that specific measures, such as cortical surface area and cortical thickness, reflect different underlying neural architectures, the literature regarding these different measures in individuals with nonspecific low back pain is limited. Therefore, the current study was designed to investigate the association between the performance on a sensorimotor task, more specifically the sit-to-stand-to-sit task, and cortical surface area and cortical thickness in individuals with nonspecific low back pain and healthy controls.

MATERIALS AND METHODS

Seventeen individuals with nonspecific low back pain and 17 healthy controls were instructed to perform 5 consecutive sit-to-stand-to-sit movements as fast as possible. In addition, T1-weighted anatomic scans of the brain were acquired and analyzed with FreeSurfer.

RESULTS

Compared with healthy controls, individuals with nonspecific low back pain needed significantly more time to perform 5 sit-to-stand-to-sit movements (P < .05). Brain morphometric analyses revealed that cortical thickness of the ventrolateral prefrontal cortical regions was increased in patients with nonspecific low back pain compared with controls. Furthermore, decreased cortical thickness of the rostral anterior cingulate cortex was associated with lower sit-to-stand-to-sit performance on an unstable support surface in individuals with nonspecific low back pain and healthy controls (r = -0.47, P < .007). In addition, a positive correlation was found between perceived pain intensity and cortical thickness of the superior frontal gyrus (r = 0.70, P < .002) and the pars opercularis of the inferior ventrolateral prefrontal cortex (r = 0.67, P < .004). Hence, increased cortical thickness was associated with increased levels of pain intensity in individuals with nonspecific low back pain. No associations were found between cortical surface area and the pain characteristics in this group.

CONCLUSIONS

The current study suggests that cortical thickness may contribute to different aspects of sit-to-stand-to-sit performance and perceived pain intensity in individuals with nonspecific low back pain.

Structural Brain Connectivity and the Sit-to-Stand-to-Sit Performance in Individuals with Nonspecific Low Back Pain: A Diffusion Magnetic Resonance Imaging-Based Network Analysis

Individuals with nonspecific low back pain (NSLBP) show an impaired sensorimotor control. They need significantly more time to perform five consecutive sit-to-stand-to-sit (STSTS) movements compared with healthy controls. Optimal sensorimotor control depends on the coactivation of many brain regions, which have to operate as a coordinated network to achieve correct motor output. Therefore, the examination of brain connectivity from a network perspective is crucial for understanding the factors that drive sensorimotor control. In the current study, potential alterations in structural brain networks of individuals with NSLBP and the correlation with the performance of the STSTS task were investigated. Seventeen individuals with NSLBP and 17 healthy controls were instructed to perform five consecutive STSTS movements as fast as possible. In addition, data of diffusion magnetic resonance imaging were acquired and analyzed using a graph theoretical approach. Results showed that individuals with NSLBP needed significantly more time to perform the STSTS task compared with healthy controls (p < 0.05). Both groups exhibited small-world properties in their structural networks. However, local efficiency was significantly decreased in the patients with NSLBP compared with controls (p < 0.05, false discovery rate [FDR] corrected). Moreover, global efficiency was significantly correlated with the sensorimotor task performance within the NSLBP group (r = -0.73, p = 0.002). Our data show disrupted network organization of white matter networks in patients with NSLBP, which may contribute to their persistent pain and sensorimotor disabilities.

Revisiting the Corticomotor Plasticity in Low Back Pain: Challenges and Perspectives

Chronic low back pain (CLBP) is a recurrent debilitating condition that costs billions to society. Refractoriness to conventional treatment, lack of improvement, and associated movement disorders could be related to the extensive brain plasticity present in this condition, especially in the sensorimotor cortices. This narrative review on corticomotor plasticity in CLBP will try to delineate how interventions such as training and neuromodulation can improve the condition. The review recommends subgrouping classification in CLBP owing to brain plasticity markers with a view of better understanding and treating this complex condition.

Resting-State Functional Connectivity of the Sensorimotor Network in Individuals with Nonspecific Low Back Pain and the Association with the Sit-to-Stand-to-Sit Task

Individuals with nonspecific low back pain (NSLBP) show a decreased sit-to-stand-to-sit (STSTS) performance. This dynamic sensorimotor task requires integration of sensory and motor information in the brain. Therefore, a better understanding of the underlying central mechanisms of impaired sensorimotor performance and the presence of NSLBP is needed. The aims of this study were to characterize differences in sensorimotor functional connectivity in individuals with NSLBP and to investigate whether the patterns of sensorimotor functional connectivity underlie the impaired STSTS performance. Seventeen individuals with NSLBP and 17 healthy controls were instructed to perform five consecutive STSTS movements as fast as possible. Based on the center of pressure displacement, the total duration of the STSTS task was determined. In addition, resting-state functional connectivity images were acquired and analyzed on a multivariate level using both functional connectivity density mapping and independent component analysis. Individuals with NSLBP needed significantly more time to perform the STSTS task compared to healthy controls. In addition, decreased resting-state functional connectivity of brain areas related to the integration of sensory and/or motor information was shown in the individuals with NSLBP. Moreover, the decreased functional connectivity at rest of the left precentral gyrus and lobule IV and V of the left cerebellum was associated with a longer duration of the STSTS task in both individuals with NSLBP and healthy controls. In summary, individuals with NSLBP showed a reorganization of the sensorimotor network at rest, and the functional connectivity of specific sensorimotor areas was associated with the performance of a dynamic sensorimotor task.

Associations between Proprioceptive Neural Pathway Structural Connectivity and Balance in People with Multiple Sclerosis

Mobility and balance impairments are a hallmark of multiple sclerosis (MS), affecting nearly half of patients at presentation and resulting in decreased activity and participation, falls, injuries, and reduced quality of life. A growing body of work suggests that balance impairments in people with mild MS are primarily the result of deficits in proprioception, the ability to determine body position in space in the absence of vision. A better understanding of the pathophysiology of balance disturbances in MS is needed to develop evidence-based rehabilitation approaches. The purpose of the current study was to (1) map the cortical proprioceptive pathway in vivo using diffusion-weighted imaging and (2) assess associations between proprioceptive pathway white matter microstructural integrity and performance on clinical and behavioral balance tasks. We hypothesized that people with MS (PwMS) would have reduced integrity of cerebral proprioceptive pathways, and that reduced white matter microstructure within these tracts would be strongly related to proprioceptive-based balance deficits. We found poorer balance control on proprioceptive-based tasks and reduced white matter microstructural integrity of the cortical proprioceptive tracts in PwMS compared with age-matched healthy controls (HC). Microstructural integrity of this pathway in the right hemisphere was also strongly associated with proprioceptive-based balance control in PwMS and controls. Conversely, while white matter integrity of the right hemisphere’s proprioceptive pathway was significantly correlated with overall balance performance in HC, there was no such relationship in PwMS. These results augment existing literature suggesting that balance control in PwMS may become more dependent upon (1) cerebellar-regulated proprioceptive control, (2) the vestibular system, and/or (3) the visual system.