[Cerebral reorganization in chronic low back pain and neurostimulation to improve motor control]

Brain and muscles magnetic stimulation in a drug-free case of Parkinson's disease: Motor improvements concomitant to neuroplasticty

Noninvasive stimulation of the nervous system is of growing interest in Parkinson's disease (PD) to slow-down motor decline and decrease medication and its side-effects. Repetitive transcranial magnetic stimulation (rTMS) used in PD to modulate the excitability of the primary motor cortex (M1) provided controversial results, in part because of interactions with medication. This warrants to administer rTMS in drug-free patients. Repetitive peripheral magnetic stimulation (rPMS of muscles) has not yet been tested in PD. Its influence on M1 plasticity (as tested by TMS, transcranial magnetic stimulation) and sensorimotor disorders in other health conditions makes it worth be explored in PD. Thus, rTMS and rPMS were tested in a drug-free woman (52 years old, PD-diagnosed 10 years ago) in four different rTMS + rPMS combinations (one week apart): sham-sham, real-real, real-sham, sham-real. rTMS was applied over M1 contralateral to the most impaired bodyside, and rPMS on muscles of the legs, trunk, and arms, bilaterally. M1 plasticity (TMS measures) and motor symptoms and function (clinical outcomes) were measured at different timepoints. The real-real session induced the largest motor improvements, with possible summation of effects between sessions, and maintenance at follow-up (80 days later). This was paralleled by changes of M1 facilitation and inhibition. This sheds a new light on the link between TMS measures of M1 plasticity and motor changes in PD and informs on the remaining potential for neuroplasticity and functional improvement after 10 years of PD with no antiparkinsonian drug. De novo patients with PD (drug-free) should be motivated to participate in future randomized clinical trials to further test the slow-down or delay of motor decline under noninvasive neurostimulation regimens, whatever the stage of the disease.

Cortical Mechanisms Underlying Effects of Repetitive Peripheral Magnetic Stimulation on Dynamic and Static Postural Control in Patients with Chronic Non-Specific Low Back Pain: A Double-Blind Randomized Clinical Trial

INTRODUCTION

Patients with chronic non-specific low back pain (CNLBP) often experience impaired postural control, contributing to pain recurrence. Although repetitive peripheral magnetic stimulation (rPMS) combined with core muscle training (CMT) could improve postural control, its neural mechanism remains unclear. This study aims to investigate the postural control-related cortical mechanism of the effect of rPMS on patients with CNLBP.

METHODS

This unicentric, prospective, randomized, double-blind, controlled trial was conducted in a public hospital from May to December 2023. A total of 40 patients (27 females and 13 males, mean age 29.38 ± 7.72) with CNLBP were randomly assigned to either the rPMS group (real rPMS with CMT) or the sham-rPMS group (sham-rPMS with CMT) for 12 sessions over 4 weeks. The rPMS was applied to the lumbar paravertebral multifidus muscle on the painful side. Pain and disability were quantified using the visual analog scale (VAS) and Oswestry dysfunction index (ODI) pre- and post-intervention. Furthermore, the sway area and velocity of the center of pressure (COP) were measured using a force platform. The cortical activities in 6 regions of interest during 4 tasks (standing with eyes open/closed on a stable/unstable plane) were recorded by functional near-infrared spectroscopy (fNIRS) pre- and post-intervention. The repeated measure ANOVA was applied for statistical analysis. Spearman's correlation was used to determine the relationships between variables.

RESULTS

After the intervention, the rPMS group showed decreased pain intensity (p = 0.001) and sway area (unstable eyes-closed task) (p = 0.046) compared to the sham-rPMS group. Additionally, the rPMS group exhibited increased activation in left primary motor cortex (M1) (p = 0.042) and reduced in left supplementary motor area (SMA) (p = 0.045), whereas the sham-rPMS group showed no significant changes. The increased activation of left M1 was negatively correlated to the reduction of pain intensity (r = - 0.537, p = 0.018) and sway area (r = - 0.500, p = 0.029) under the static balancing task. Furthermore, there was a positive correlation between sway velocity and VAS (r = 0.451, p = 0.046) post-rPMS intervention.

CONCLUSION

Repetitive peripheral magnetic stimulation combined with core muscle training demonstrated better analgesic effects and postural control improvements, compared to sham-stimulation. This may be attributed to the increased activation of the left primary motor cortex.

CLINICAL TRIAL REGISTRATION

The trial was registered on ClinicalTrials.gov (ChiCTR2300070943).

Body awareness disturbances in patients with low back pain: a systematic review

BACKGROUND

The pain-neuroscience literature has recently emphasized body perception or awareness. Impaired body perception results have been reported in many different chronic pain problems. Studies have reported that individuals with low back pain (LBP) also have body perception disturbances related to the lumbar spine.

OBJECTIVES

This review aimed to determine the evidence that body awareness alterations in individuals with LBP.

DESIGN

Systematic review.

METHOD

Studies were searched in PubMed, Cochrane Library, and Pedro databases up to January 2021. Each database was searched independently, according to a specific iteration research string. The protocol record of the systematic review was entered into the PROSPERO system.

RESULTS

Nine studies were included in this research. We found evidence to support more perceptual impairments in patients with LBP than healthy counterparts. In addition, the results of the studies showed an association between disrupted body awareness and pain severity, pain catastrophizing, and disability.

CONCLUSIONS

Body perception disturbances in LBP seem to be a promising path that needs to be further explored, with the ultimate goal of developing treatment contents targeting body awareness as a more comprehensive and valid evaluation and therapeutic method.

TRIAL REGISTRATION

The registration number was CRD42021235934.

Structural, Functional and Neurochemical Cortical Brain Changes Associated with Chronic Low Back Pain

Chronic low back pain (CLBP) is one of the most prevalent musculoskeletal disorders, being one of the leading contributors to disability worldwide and involving an important economic and social burden. Up to 90% of CLBP is non-specific (not associated with specific injuries), with a chronicity expectation estimated at 10%. Currently, motivational and emotional central circuits are being investigated due to their role in CLBP persistency and chronification. Therefore, this narrative review aimed to summarize the evidence regarding the cortical brain changes described for proposing novel multidisciplinary approaches. Novel advances in neuroimaging techniques demonstrated structural (e.g., decrease in the grey matter located at the dorsolateral prefrontal cortex), functional (e.g., connectivity impairments in those areas involved in pain processing), and neurochemical changes (e.g., decrease in cerebral metabolites). In addition, significant changes were found in the primary somatosensory and motor cortex, contributing to the alteration of low back muscles activation and function.

Influence of kinesiophobia on pain intensity, disability, muscle endurance, and position sense in patients with chronic low back pain-a case-control study

Background

Patients with chronic low back pain (CLBP) frequently present with kinesiophobia. Though large body of evidence reported the impact of kinesiophobia in patients with CLBP, there are paucity of studies in associating kinesiophobia to muscle endurance and position sense in patients with CLBP. The primary aim of the study is to compare the impact of kinesiophobia on lumbar extensor endurance, position sense in patient with CLBP, and asymptomatic individuals. Secondarily, we aim to examine the association between kinesiophobia and lumbar extensor endurance, position sense, pain intensity, and functional ability in patients with CLBP. Thirdly, we aim to assess the degree of association of various factors on CLBP, lumbar endurance, and position sense.

Material and methods

This case-control study will have 200 patients with CLBP and 400 controls. Kinesiophobia, lumbar endurance, and lumbar position sense will be assessed with Tampa Scale, Soren’s lumbar extensor test, and lumbar repositioning test respectively. Secondarily, the pain intensity will be assessed with visual analog scale and functional ability with Patient-specific Functional Scale in patients with CLBP. Lumbar endurance and joint position sense will be compared between subjects with and without kinesiophobia. Kinesiophobia scores will be compared with lumbar extensor endurance and proprioception joint position errors, pain intensity, and functional ability. Simple and multiple binary logistic regression will be used to determine crude and adjusted odd’s ratio for kinesiophobia, lumbar position sense and kinesiophobia, and lumbar endurance.

Discussion

The finding from this study can be generalized as this study has adequate sample size and subgroup analysis by adjusting the variables to draw a valid conclusion. The finding of this study will help the working physician to include assessment of kinesiophobia as part of musculoskeletal evaluation for patient with CLBP in a prospective diagnostic intervention.

Trial registration

ClinicalTrials.gov NCT05079893. Registered on 14 October 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06406-6.

Checklist on the Quality of the Repetitive Peripheral Magnetic Stimulation (rPMS) Methods in Research: An International Delphi Study

An increasing number of clinical research studies have used repetitive peripheral magnetic stimulation (rPMS) in recent years to alleviate pain or improve motor function. rPMS is non-invasive, painless, and administrated over peripheral nerve, spinal cord roots, or a muscle using a coil affixed to the skin and connected to a rapid-rate magnetic stimulator. Despite the clinical impact and scientific interest, the methodological inconsistencies or incomplete details and findings between studies could make the rPMS demonstration difficult to replicate. Given the lack of guidelines in rPMS literature, the present study aimed at developing a checklist to improve the quality of rPMS methods in research. An international panel of experts identified among those who had previously published on the topic were enrolled in a two-round web-based Delphi study with the aim of reaching a consensus on the items that should be reported or controlled in any rPMS study. The consensual rPMS checklist obtained comprises 8 subject-related items (e.g., age, sex), 16 methodological items (e.g., coil type, pulse duration), and 11 stimulation protocol items (e.g., paradigm of stimulation, number of pulses). This checklist will contribute to new interventional or exploratory rPMS research to guide researchers or clinicians on the methods to use to test and publish rPMS after-effects. Overall, the checklist will guide the peer-review process on the quality of rPMS methods reported in a publication. Given the dynamic nature of a consensus between international experts, it is expected that future research will affine the checklist.

Theta-Burst Stimulation of Forearm Muscles in Patients With Complex Regional Pain Syndrome: Influence on Brain and Clinical Outcomes

Objective: Complex regional pain syndrome (CRPS) is a common pain condition characterized by the changes in the brain that are not yet addressed by conventional treatment regimens. Repetitive peripheral magnetic stimulation (rPMS) of muscles is painless and non-invasive and can influence these changes (the induction of brain plasticity) to reduce pain and improve motricity. In patients with CRPS, this open-label pilot study tested rPMS after-effects on the pain intensity and sensorimotor control of the upper limb along with the excitability changes of the primary motor cortex (M1).

Methods: Eight patients with CRPS were enrolled in a single-session program. Patients were tested at pre- and post-rPMS over the flexor digitorum superficialis (FDS) muscle. The clinical outcomes were pain intensity, proprioception, active range of motion (ROM), and grip strength. M1 excitability was tested using the single- and paired-pulse transcranial magnetic stimulation (TMS) of M1.

Results: In our small sample study, rPMS reduced instant and week pain, improved proprioception and ROM, and reduced the hemispheric imbalance of several TMS outcomes. The more M1 contralateral to the CRPS side was hyperactivated at baseline, the more pain was reduced.

Discussion: This open-label pilot study provided promising findings for the use of rPMS in CRPS with a focus on M1 plastic changes. Future randomized, placebo-controlled clinical trials should confirm the existence of a causal relationship between the TMS outcomes and post-rPMS decrease of pain. This will favor the development of personalized treatments of peripheral non-invasive neurostimulation in CRPS.

Complex Regional Pain Syndrome. A Comprehensive Review on Neuroplastic Changes Supporting the Use of Non-invasive Neurostimulation in Clinical Settings

Background: Complex regional pain syndrome (CRPS) is a rare debilitating disorder characterized by severe pain affecting one or more limbs. CRPS presents a complex multifactorial physiopathology. The peripheral and sensorimotor abnormalities reflect maladaptive changes of the central nervous system. These changes of volume, connectivity, activation, metabolism, etc., could be the keys to understand chronicization, refractoriness to conventional treatment, and developing more efficient treatments. Objective: This review discusses the use of non-pharmacological, non-invasive neurostimulation techniques in CRPS, with regard to the CRPS physiopathology, brain changes underlying chronicization, conventional approaches to treat CRPS, current evidence, and mechanisms of action of peripheral and brain stimulation. Conclusion: Future work is warranted to foster the evidence of the efficacy of non-invasive neurostimulation in CRPS. It seems that the approach has to be individualized owing to the integrity of the brain and corticospinal function. Non-invasive neurostimulation of the brain or of nerve/muscles/spinal roots, alone or in combination with conventional therapy, represents a fertile ground to develop more efficient approaches for pain management in CRPS.

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.

Corticomotor control of deep abdominal muscles in chronic low back pain and anticipatory postural adjustments

Contralateral transversus abdominis muscle (cTrA) is known to be anticipatory to rapid focal movement. The activation of ipsilateral TrA (iTrA) follows cTrA, but their anticipatory interaction in healthy subjects seems to be delayed in low back pain (LBP) patients. TrA delay in LBP is linked with reorganization of the primary motor cortex (M1), thus supporting that cortical changes underlie the altered postural control. Our study tested whether differences in postural adjustments were present in LBP for TrA onsets and co-activation, and whether these differences were paralleled by cortical motor changes. Thirteen chronic LBP patients and 9 healthy Controls were enrolled. Surface recordings of cTrA/internal oblique (IO) and iTrA/IO were collected during a rapid shoulder flexion task while standing. Transcranial magnetic stimulation of M1 tested TrA/IO corticospinal excitability, active motor threshold and short-interval intracortical inhibition (SICI). In LBP compared to Controls, iTrA/IO activation was delayed, co-activation was absent, timing between TrA/IO onsets was impaired, and SICI was missing. Between-outcomes correlations observed in one group were not significant in the other. Delay of iTrA/IO and the lacking co-activation were not explained by between-group differences of transcranial magnetic stimulation outcomes. TrA/IO co-activation is present during rapid focal movement in healthy subjects only. LBP patients displayed an important alteration of the control of spine stability that can be explained by altered mechanisms of M1 motor programming.