Primary somatosensory/motor cortical thickness distinguishes paresthesia-dominant from pain-dominant carpal tunnel syndrome

Altered brain function and structure in carpal tunnel syndrome: a systematic review and meta-analysis of structural and functional brain imaging

This systematic review with a meta-analysis aimed to identify the altered brain structure and function in carpal tunnel syndrome (CTS) by summarizing the literature about magnetic resonance imaging (MRI), functional magnetic resonance imaging (fMRI), and magnetoencephalography (MEG) outcomes compared to healthy controls (HC). CTS is the most common nerve entrapment in the arm associated with altered peripheral and central nociceptive system. PRISMA guidelines were used to report the outcomes. Six databases were searched for relevant literature (Web of Science, Scopus, PubMed, Sage, EBSCO host, and Cochrane). Eligible studies comparing MRI, fMRI, and MEG findings in people with CTS (present for at least 2 months) and HC through the following parameters: (1) interdigit cortical separation distance, (2) white and grey matter changes, (3) peak latency of M20 wave and recovery function of N20 from the somatosensory cortex (SI), and (4) surface area of activated digit cortical representation. The results from different studies were pooled and a meta-analysis was done. From 17 included, there was a significant reduction of interdigit cortical separation distance of index-middle and index-little fingers in the CTS (SMD = - 0.869, 95% CI (- 1.325, - 0.413), p-value = 0.000) and (SMD = - 0.79, 95% CI (- 1.217, - 0.364), p-value = 0.000), respectively. Middle-little fingers interdigit separation showed no difference (SMD = - 0.2, 95% CI (- 0.903, 1.309), p-value = 0.718). There is evidence supporting the altered brain structure and function in CTS as evidenced by reduction of interdigit cortical separation distance, and excessive blurring and disinhibition of SI, with low resting state functional connectivity. Thus, centrally directed therapeutic approaches might complement peripheral treatments.

Effects of mirror therapy on pain, sensitivity and functionality in patients with unilateral carpal tunnel syndrome. Randomised control trial

PURPOSE

To investigate the effects of mirror therapy (MT) and therapeutic exercise (TE) with the unaffected hand, on pain, sensitivity and functionality in individuals with unilateral carpal tunnel syndrome (CTS).

MATERIAL AND METHODS

A randomized controlled trial was carried out. Thirty-nine adults with unilateral CTS were included and randomly allocated to a six-week training programme based on MT (n = 20) or TE (n = 19). Visual Analogue Scale, Semmes-Weinstein monofilament test, Two-point discrimination (2PD), Disabilities of the Arm, Shoulder and Hand (DASH) and Boston Carpal Tunnel Questionnaire (BCTQ) were assessed before (T0) and after the intervention (T1), and at one-month follow-up (T2).

RESULTS

At T1, MT and TE showed significant improvements in pain (p = 0.001 and p = 0.03, respectively), however, only MT maintained the achieved effects at T2 (p = 0.01). In addition, 2PD significantly improved in MT in the first (p = 0.04) and fourth fingers (p = 0.02) at T1. The DASH score decreased at T1 in MT (p < 0.001) and TE (p = 0.01). Additionally, the BCTQ score improved in MT (p < 0.001), and TE (p < 0.001) at T1. The effects were maintained at T2 for DASH and BCTQ scores.

CONCLUSIONS

Training of the unaffected hand resulted in a significant improvement of the affected hand in both groups; nevertheless, MT achieved a longer duration of the effects.

Motor Imagery and Pain Processing in Patients With Entrapment Neuropathies: A Cross-sectional Study

OBJECTIVES

(1) To assess the ability to generate both kinesthetic and visual motor imagery in participants with carpal tunnel syndrome (CTS), compared with asymptomatic participants. (2) To assess the influence of psychophysiological and functional variables in the motor imagery process.

METHODS

Twenty patients with unilateral CTS and 18 pain-free individuals were recruited. An observational case-control study with a nonprobability sample was conducted to assess visual and kinesthetic movement imagery ability and psychophysiological variables in patients with CTS compared with asymptomatic participants in a control group. The trial was conducted in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology statement.

RESULTS

CTS patients have more difficulties in generating visual motor images compared with asymptomatic individuals ( t =-2.099; P <0.05; d=0.70). They need more time to complete the mental tasks (visual t =-2.424; P <0.05 and kinesthetic t =-2.200; P <0.05). A negative correlation was found between the ability to imagine and functional deficits ( r =-0.569; P =0.021) for the kinesthetic subscale and temporal summation ( r =-0.515; P <0.5). A positive correlation was found between pain pressure threshold homolateral (homolateral) and time to generate the visual mental images ( r =0.537; P <0.05).

DISCUSSION

CTS patients have greater difficulty generating motor images than asymptomatic individuals. Patients also spend more time during mental tasks. CTS patients present a relationship between temporal summation and the capacity to generate kinesthetic images. In addition, the CST patients presented a correlation between chronometry mental tasking and mechanical hyperalgesia.

Cortical abnormalities in patients with fibromyalgia: a pilot study of surface-based morphometry analysis

BACKGROUND

Although neuroanatomical studies correlated to fibromyalgia (FM) are gaining increasing interest, the cortical morphology of patients are largely unknown, and data on cortical gyrification are scarce. The objective of the present study is to assess the cortical morphology in female patients with FM compared with healthy controls (HC) using surface-based morphometry (SBM) analysis of magnetic resonance imaging (MRI).

METHODS

T1-MRIs and clinical data of 20 FM patients and 20 HC subjects were obtained from a public databset via OpenNeuro. For each subject, surface parameters including cortical thickness, local gyrification index (LGI), sulcal depth, and fractal dimensionality were estimated using SBM analysis. These data were compared between two groups controlled by age. The correlations between regional SBM parameters showing group differences and clinical profiles were analyzed.

RESULTS

Compared with HC subjects, FM patients showed reduced cortical thickness in right primary motor cortex, lower LGI in right rostral anterior cingulate and higher sulcal depth in right precuneus (p < 0.05 cluster level family- wise error corrected). In FM patients, correlation analysis showed that the cortical thickness in right primary motor cortex were inversely correlated with scores of pain catastrophizing scale (r = -0.498, p = 0.030) and pain self-perception scale (r = -0.527, p = 0.020), and disease duration (r = -0.488, p = 0.034), respectively.

CONCLUSIONS

Our findings provide evidence of neuroanatomical aberrations in FM patients, which may provide insight into the neuropathology of FM.

Brain Network Changes in Lumbar Disc Herniation Induced Chronic Nerve Roots Compression Syndromes

Lumbar disc herniation (LDH) induced nerve compression syndromes have been a prevalent problem with complex neural mechanisms. Changes in distributed brain areas are involved in the occurrence and persistence of syndromes. The present study aimed to investigate the changes of brain functional network in LDH patients with chronic sciatica using graph theory analysis. A total of thirty LDH adults presenting L4 and/or L5 root (s) compression syndromes (LDH group) and thirty age-, sex-, BMI- and education-matched healthy control (HC group) were recruited for functional MRI scan. Whole-brain functional network was constructed for each participant using Pearson's correlation. Global and nodal properties were calculated and compared between two groups, including small-worldness index, clustering coefficient, characteristic path length, degree centrality (DC), betweenness centrality (BC) and nodal efficiency. Both LDH and HC groups showed small-world architecture in the functional network of brain. However, LDH group showed that nodal centralities (DC, BC and nodal efficiency) increased in opercular part of inferior frontal gyrus; and decreased in orbital part of inferior frontal gyrus, lingual cortex and inferior occipital gyrus. The DC and efficiency in the right inferior occipital gyrus were negatively related with the Oswestry Disability Index in LDH group. In conclusion, the LDH-related chronic sciatica syndromes may induce regional brain alterations involving self-referential, emotional responses and pain regulation functions. But the whole-brain small-world architecture was not significantly disturbed. It may provide new insights into LDH patients with radicular symptoms from new perspectives.

Toward Composite Pain Biomarkers of Neuropathic Pain—Focus on Peripheral Neuropathic Pain

Chronic pain affects ~10–20% of the U.S. population with an estimated annual cost of $600 billion, the most significant economic cost of any disease to-date. Neuropathic pain is a type of chronic pain that is particularly difficult to manage and leads to significant disability and poor quality of life. Pain biomarkers offer the possibility to develop objective pain-related indicators that may help diagnose, treat, and improve the understanding of neuropathic pain pathophysiology. We review neuropathic pain mechanisms related to opiates, inflammation, and endocannabinoids with the objective of identifying composite biomarkers of neuropathic pain. In the literature, pain biomarkers typically are divided into physiological non-imaging pain biomarkers and brain imaging pain biomarkers. We review both types of biomarker types with the goal of identifying composite pain biomarkers that may improve recognition and treatment of neuropathic pain.

Altered brain activity in end-stage knee osteoarthritis revealed by resting-state functional magnetic resonance imaging

INTRODUCTION

Knee osteoarthritis (KOA) is characterized by a degenerative change of knee cartilage and secondary bone hyperplasia, resulting in pain, stiffness, and abnormal walking gait. Long-term chronic pain causes considerable cortical plasticity alternations in patients. However, the brain structural and functional alterations associated with the pathological changes in knee joints of end-stage KOA patients remain unclear. This study aimed to analyze the structural and functional connectivity alterations in end-stage KOA to comprehensively understand the main brain-associated mechanisms underlying its development and progression.

METHODS

In this study, 37 patients with KOA and 37 demographically matched healthy controls (HCs) were enrolled. Alternations in gray matter (GM) volume in patients with KOA were determined using voxel-based morphometry. The region with the largest GM volume alteration was selected as the region of interest to calculate the voxel-wise resting-state functional connectivity (rs-FC) in the two groups. Pearson's correlation coefficient was used to analyze the correlation between clinical measures and GM volume alternations in patients with KOA.

RESULTS

Compared with HCs, patients with KOAs exhibited significantly decreased GM volumes in the left middle temporal gyrus (left-MTG) and the left inferior temporal gyrus. Results of the voxel-wise rs-FC analysis revealed that compared with HCs, patients with KOA had decreased left-MTG rs-FC to the right dorsolateral superior frontal gyrus, left middle frontal gyrus, and left medial superior frontal gyrus. GM volume in the left-MTG was negatively correlated with the Western Ontario and McMaster Universities Arthritis Index in patients with KOA (r = -0.393, p = .016).

CONCLUSION

Structural remodeling and functional connectivity alterations may be one of the central brain mechanisms associated with end-stage KOA.

Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes

ABSTRACT

Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. Based on an a priori published protocol and using PRISMA guidelines, 7 databases were searched (Embase, Web of Science, Scopus, PubMed, SAGE, EBSCOhost, and ProQuest). Eligible studies compared the QST findings of individuals with subacute and chronic CTS with those of healthy controls through thermal, mechanical, and vibration detection thresholds; thermal, pressure, and mechanical pain thresholds; mechanical pain sensitivity; presence of allodynia; wind-up ratio; and conditioned pain modulation. Thirty-seven studies were included in the qualitative analysis. Results showed a significant loss of all detection thresholds of hand median nerve territories and hand extramedian areas (little finger and hand dorsum) in CTS (P < 0.05) but no significant difference (P > 0.05) in wind-up ratio, cold, heat, or mechanical pain thresholds of the median nerve territories. Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm (P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area (P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.

Responsiveness of quantitative sensory testing-derived sensory phenotype to disease-modifying intervention in patients with entrapment neuropathy: a longitudinal study

ABSTRACT

The German Research Network on Neuropathic Pain (DFNS) quantitative sensory testing (QST) method for sensory phenotyping is used to stratify patients by mechanism-associated sensory phenotype, theorised to be predictive of intervention efficacy. We hypothesised that change in pain and sensory dysfunction would relate to change in sensory phenotype. We investigated the responsiveness of sensory phenotype to surgery in patients with an entrapment neuropathy. With ethical approval and consent, this observational study recruited patients with neurophysiologically confirmed carpal tunnel syndrome. Symptom and pain severity parameters and DFNS QST were evaluated before and after carpal tunnel surgery. Surgical outcome was evaluated by patient-rated change. Symptom severity score of the Boston Carpal Tunnel Questionnaire and associated pain and paraesthesia subgroups were comparators for clinically relevant change. Quantitative sensory testing results (n = 76) were compared with healthy controls (n = 54). At 6 months postsurgery, 92% participants reported a good surgical outcome and large decrease in pain and symptom severity (P < 0.001). Change in QST parameters occurred for thermal detection, thermal pain, and mechanical detection thresholds with a moderate to large effect size. Change in mechanical pain measures was not statistically significant. Change occurred in sensory phenotype postsurgery (P < 0.001); sensory phenotype was associated with symptom subgroup (P = 0.03) and patient-rated surgical outcome (P = 0.02). Quantitative sensory testing-derived sensory phenotype is sensitive to clinically important change. In an entrapment neuropathy model, sensory phenotype was associated with patient-reported symptoms and demonstrated statistically significant, clinically relevant change after disease-modifying intervention. Sensory phenotype was independent of disease severity and may reflect underlying neuropathophysiology.

S1 Brain Connectivity in Carpal Tunnel Syndrome Underlies Median Nerve and Functional Improvement Following Electro-Acupuncture

Carpal Tunnel Syndrome (CTS) is a median nerve entrapment neuropathy that alters primary somatosensory cortex (S1) organization. While electro-acupuncture (EA), a form of peripheral neuromodulation, has been shown to improve clinical and neurophysiological CTS outcomes, the role of EA-evoked brain response during therapy (within and beyond S1) for improved outcomes is unknown. We investigated S1-associated whole brain fMRI connectivity during both a resting and sustained EA stimulation state in age-matched healthy controls (N = 28) and CTS patients (N = 64), at baseline and after 8 weeks of acupuncture therapy (local, distal, or sham EA). Compared to healthy controls, CTS patients at baseline showed decreased resting state functional connectivity between S1 and thalamic pulvinar nucleus. Increases in S1/pulvinar connectivity strength following verum EA therapy (combined local and distal) were correlated with improvements in median nerve velocity (r = 0.38, p = 0.035). During sustained local EA, compared to healthy controls, CTS patients demonstrated increased functional connectivity between S1 and anterior hippocampus (aHipp). Following 8 weeks of local EA therapy, S1/aHipp connectivity significantly decreased and greater decrease was associated with improvement in patients' functional status (r = 0.64, p = 0.01) and increased median nerve velocity (r = -0.62, p = 0.013). Thus, connectivity between S1 and other brain areas is also disrupted in CTS patients and may be improved following EA therapy. Furthermore, stimulus-evoked fMRI connectivity adds therapy-specific, mechanistic insight to more common resting state connectivity approaches. Specifically, local EA modulates S1 connectivity to sensory and affective processing regions, linked to patient function and median nerve health.

Structural white matter alterations in carpal tunnel syndrome: A modified TBSS study

Functional and structural brain alterations have been noted in carpal tunnel syndrome (CTS), the most common entrapment peripheral neuropathy. Previous studies were mainly focused on somatosensory cortices. However, the changes of white matter diffusion properties in nonsensorimotor cortices remain uninvestigated. We utilized a modified tract-based spatial statistics (TBSS) pipeline to explore CTS-related white matter plasticity, omitting the skeletonization step and registering diffusion tensor imaging (DTI) data to a study-specific, high resolution T1 template by an optimized registration method. The modified TBSS was demonstrated to be more sensitive to detect changes in white matter integrity than the standard TBSS approach. In this study, 25 moderate/severe CTS patients and 17 age- and sex-matched healthy controls (HC) were evaluated with DTI. Fractional anisotropy (FA) and radial diffusivity (RD) were calculated for group comparison. And the relationship between diffusion parameters and clinical assessments was also analyzed. Comparing with the healthy controls, CTS patients showed significantly increased FA and decreased RD in areas of multisensory integration and motor control involving the central opercular cortex and supplementary motor area (SMA) of the dominant hemisphere. Moreover, altered diffusion parameters in the central opercular cortex of the dominant hemisphere were significantly correlated with Boston Carpal Tunnel Questionnaire (BCTQ) scores. It is considered to be a form of maladaptive neuroplastic response to CTS-associated afference and motor control deficits. Such insight may be helpful in developing new strategies for the treatment of CTS.

Measurement properties of the Boston Carpal Tunnel Questionnaire in subjects with neurophysiological confirmation of carpal tunnel syndrome: a Rasch analysis perspective

PURPOSE

To perform a comprehensive psychometric analysis of the Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) by means of factor and Rasch analyses in subjects with neurophysiologic confirmation of carpal tunnel syndrome (CTS). Relationship between clinical severity assessed with the log-linear version of the BCTQ and neurophysiologic severity assessed with nerve conduction studies was further examined.

METHODS

Five hundred and twenty-eight individuals completed the questionnaire. Confirmatory and exploratory factor analyses were used to determine the latent structure of the BCTQ. Through Rasch methodology, a log-linear version was proposed given the latent structure of the questionnaire. Linear relationship between the proposed questionnaire and neurophysiologic findings was established.

RESULTS

The BCTQ underlying structure comprises, at least, three factors that may be represented by Functionality, Paresthesia and Pain domains. Two log-linear subscales may be proposed: subscale 1 comprised of the Functionality factor and subscale 2 which incorporates the Paresthesia and Pain factors under a bifactor solution. Neurophysiologic and clinical severity classification system displays a very weak linear correlation.

CONCLUSION

A log-linear version of the BCTQ, useful as an outcome tool in clinical and trial settings, is proposed. Neurophysiological data lack the ability to resemble changes in clinical status of individuals with CTS.

Chronic musculoskeletal impairment is associated with alterations in brain regions responsible for the production and perception of movement

KEY POINTS

Massive irreparable rotator cuff tear was used as a model to study the impact of chronic pain and motor impairment on the motor systems of the human brain using magnetic resonance imaging. Patients show markers of lower grey/white matter integrity and lower functional connectivity compared with control participants in regions responsible for movement and the perception of visual movement and body shape. An independent cohort of patients showed relative deficits in the perception of visual motion and hand laterality compared with an age-matched control group. These data support the hypothesis that the structure and function of the motor control system differs in patients who have experienced chronic motor impairment. This work also raises a new hypothesis, supported by neuroimaging and behaviour, that a loss of motor function could also be associated with off-target effects, namely a reduced ability to perceive motion and body form.

ABSTRACT

Changes in the way we move can induce changes in the brain, yet we know little of such plasticity in relation to musculoskeletal diseases. Here we use massive irreparable rotator cuff tear as a model to study the impact of chronic motor impairment and pain on the human brain. Cuff tear destabilises the shoulder, impairing upper-limb function in overhead and load-bearing tasks. We used neuroimaging and behavioural testing to investigate how brain structure and function differed in cuff tear patients and controls (imaging: 21 patients, age 76.3 ± 7.68; 18 controls, age 74.9 ± 6.59; behaviour: 13 patients, age 75.5 ± 10.2; 11 controls, age 73.4 ± 5.01). We observed lower grey matter density and cortical thickness in cuff tear patients in the postcentral gyrus, inferior parietal lobule, temporal-parietal junction and the pulvinar - areas implicated in somatosensation, reach/grasp and body form perception. In patients we also observed lower functional connectivity between the motor network and the middle temporal visual cortex (MT), a region involved in visual motion perception. Lower white matter integrity was observed in patients in the inferior fronto-occipital/longitudinal fasciculi. We investigated the cognitive domains associated with the brain regions identified. Patients exhibited relative impairment in visual body judgements and the perception of biological/global motion. These data support our initial hypothesis that cuff tear is associated with differences in the brain's motor control regions in comparison with unaffected individuals. Moreover, our combination of neuroimaging and behavioural data raises a new hypothesis that chronic motor impairment is associated with an altered perception of visual motion and body form.

Abnormal Brain Connectivity in Carpal Tunnel Syndrome Assessed by Graph Theory

Introduction

Numerous resting-state functional magnetic resonance imaging (fMRI) researches have indicated that large-scale functional and structural remodeling occurs in the whole brain despite an intact sensorimotor network after carpal tunnel syndrome (CTS). Investigators aimed to explore alterations of the global and nodal properties that occur in the whole brain network of patients with CTS based on topographic theory.

Methods

Standard-compliant fMRI data were collected from 27 patients with CTS in bilateral hands and 19 healthy control subjects in this cross-sectional study. The statistics based on brain networks were calculated the differences between the patients and the healthy. Several topological properties were computed, such as the small-worldness, nodal clustering coefficient, characteristic path length, and degree centrality.

Results

Compared to those of the healthy controls, the global properties of the CTS group exhibited a decreased characteristic path length. Changes in the local-level properties included a decreased nodal clustering coefficient in 6 separate brain regions and significantly different degree centrality in several brain regions that were related to sensorimotor function and pain.

Discussion

The study suggested that CTS reinforces global connections and makes their networks more random. The changed nodal properties were affiliated with basal ganglia-thalamo-cortical circuits and the pain matrix. These results provided new insights for improving our understanding of abnormal topological theory in relation to the functional brain networks of CTS patients.

Perspective

This article presents that the CTS patients’ brain with a higher global efficiency. And the significant alterations in several brain regions which are more related to pain and motor processes. The results provided effective complements to the neural mechanisms underlying CTS.

Neural plasticity secondary to carpal tunnel syndrome: a pseudo-continuous arterial spin labeling study

Conventional neuroimaging techniques cannot truly reflect the change of regional cerebral blood flow in patients with carpal tunnel syndrome. Pseudo-continuous arterial spinning labeling (pCASL) as an efficient non-invasive neuroimaging technique can be applied to directly quantify the neuronal activities of individual brain regions that show the persistent symptoms owing to its better spatial resolution and increased signal-to-noise ratio. Therefore, this prospective observational study was conducted in 27 eligible female carpal tunnel syndrome, aged 57.7 ± 6.51 years. Psychometric tests, nerve conduction studies and pCASL neuroimaging assessment were performed. The results showed that the relevant activated brain regions in the cortical, subcrotical, and cerebral regions were correlated with numbness, pain, functionality, median nerve status and motor amplitude of median nerve (K = 21-2849, r = -0.77-0.76, P < 0.05). There was a tendency of pain processing which shifted from the nociceptive circuitry to the emotional and cognitive one during the process of chronic pain caused by carpal tunnel syndrome. It suggests the necessity of addressing the ignored cognitive or emotional state when managing patients with carpal tunnel syndrome. Approval for this study was obtained from the Institutional Review Board of The University of Hong Kong/Hospital Authority Hong Kong West, China (HKU/HA HKW IRB, approval No. UW17-129) on April 11, 2017. This study was registered in Clinical Trial Registry of The University of Hong Kong, China (registration number: HKUCTR-2220) on April 24, 2017.

The Utilization of Joint Mobilization As Part of a Comprehensive Program to Manage Carpal Tunnel Syndrome: A Systematic Review

OBJECTIVE

The purpose of this review is to identify the role of joint mobilization for individuals with Carpal tunnel syndrome (CTS).

METHODS

A systematic search of 5 electronic databases (PubMed, CINAHL, Scopus, Cochrane Central Register of Controlled Trials, and SPORTDiscus) was performed to identify eligible full-text randomized clinical trials related to the clinical question. Joint mobilization had to be included in one arm of the randomized clinical trials to be included. Two reviewers independently participated in each step of the screening process. A blinded third reviewer assisted in cases of discrepancy. The PEDro scale was used to assess quality.

RESULTS

Ten articles were included after screening 2068 titles. In each article where joint mobilization was used, positive effects in pain, function, or additional outcomes were noted. In most cases, the intervention group integrating joint mobilization performed better than the comparison group not receiving joint techniques.

CONCLUSION

In the articles reviewed, joint mobilization was associated with positive clinical effects for persons with CTS. No studies used joint mobilization in isolation; therefore, results must be interpreted cautiously. This review indicates that joint mobilization might be a useful adjunctive intervention in the management of CTS.

Evidence for a novel subcortical mechanism for posterior cingulate cortex atrophy in HIV peripheral neuropathy

We previously reported that neuropathic pain was associated with smaller posterior cingulate cortical (PCC) volumes, suggesting that a smaller/dysfunctional PCC may contribute to development of pain via impaired mind wandering. A gap in our previous report was lack of evidence for a mechanism for the genesis of PCC atrophy in HIV peripheral neuropathy. Here we investigate if volumetric differences in the subcortex for those with neuropathic paresthesia may contribute to smaller PCC volumes, potentially through deafferentation of ascending white matter tracts resulting from peripheral nerve damage in HIV neuropathy. Since neuropathic pain and paresthesia are highly correlated, statistical decomposition was used to separate pain and paresthesia symptoms to determine which regions of brain atrophy are associated with both pain and paresthesia and which are associated separately with pain or paresthesia. HIV+ individuals (N = 233) with and without paresthesia in a multisite study underwent structural brain magnetic resonance imaging. Voxel-based morphometry and a segmentation/registration tool were used to investigate regional brain volume changes associated with paresthesia. Analysis of decomposed variables found that smaller midbrain and thalamus volumes were associated with paresthesia rather than pain. However, atrophy in the PCC was related to both pain and paresthesia. Peak thalamic atrophy (p = 0.004; MNI x = - 14, y = - 24, z = - 2) for more severe paresthesia was in a region with reciprocal connections with the PCC. This provides initial evidence that smaller PCC volumes in HIV peripheral neuropathy are related to ascending white matter deafferentation caused by small fiber damage observed in HIV peripheral neuropathy.

Reduced tactile acuity in chronic low back pain is linked with structural neuroplasticity in primary somatosensory cortex and is modulated by acupuncture therapy

Prior studies have shown that patients suffering from chronic Low Back Pain (cLBP) have impaired somatosensory processing including reduced tactile acuity, i.e. reduced ability to resolve fine spatial details with the perception of touch. The central mechanism(s) underlying reduced tactile acuity are unknown but may include changes in specific brain circuitries (e.g. neuroplasticity in the primary somatosensory cortex, S1). Furthermore, little is known about the linkage between changes in tactile acuity and the amelioration of cLBP by somatically-directed therapeutic interventions, such as acupuncture. In this longitudinal neuroimaging study, we evaluated healthy control adults (HC, N ​= ​50) and a large sample of cLBP patients (N ​= ​102) with structural brain imaging (T1-weighted MRI for Voxel-Based Morphometry, VBM; Diffusion Tensor Imaging, DTI) and tactile acuity testing using two-point discrimination threshold (2PDT) over the lower back (site of pain) and finger (control) locations. Patients were evaluated at baseline and following a 4-week course of acupuncture, with patients randomized to either verum acupuncture, two different forms of sham acupuncture (designed with or without somatosensory afference), or no-intervention usual care control. At baseline, cLBP patients demonstrated reduced acuity (greater 2PDT, P ​= ​0.01) over the low back, but not finger (P ​= ​0.29) locations compared to HC, suggesting that chronic pain affects tactile acuity specifically at body regions encoding the experience of clinical pain. At baseline, Gray Matter Volume (GMV) was elevated and Fractional Anisotropy (FA) was reduced, respectively, in the S1-back region of cLBP patients compared to controls (P ​< ​0.05). GMV in cLBP correlated with greater 2PDT-back scores (ρ ​= ​0.27, P ​= ​0.02). Following verum acupuncture, tactile acuity over the back was improved (reduced 2PDT) and greater improvements were associated with reduced S1-back GMV (ρ ​= ​0.52, P ​= ​0.03) and increased S1-back adjacent white matter FA (ρ ​= ​-0.56, P ​= ​0.01). These associations were not seen for non-verum control interventions. Thus, S1 neuroplasticity in cLBP is linked with deficits in tactile acuity and, following acupuncture therapy, may represent early mechanistic changes in somatosensory processing that track with improved tactile acuity.

Disturbance of somatotopic spatial cognition and extra-territorial pain in carpal tunnel syndrome

BACKGROUND

Several studies on carpal tunnel syndrome have reported pain that exists beyond the median nerve territory of the affected hand. However, the mechanism is unknown.

PURPOSE

We investigated the cause of extra-territorial pain by the analysis of clinical assessments and cortical activity using magnetoencephalography.

METHODS

To compare patients with and without extra-territorial pain, fourteen patients with carpal tunnel syndrome were assessed using clinical examination, such as patients' profile, paresthesia, physical tests, and psychological tests. The physical assessment included tactile threshold and static and moving two-point discrimination sensations on digital pulp. Neural activation in the cerebral cortex was also measured using z-scores calculated by magnetoencephalography.

RESULTS

Among fourteen patients, ten patients had pain in the affected median nerve territory only and four patients had extra-territorial pain. When comparing the groups, the static and moving two-point discrimination sensation values in patients with extra-territorial pain were larger than those of patients without the pain (p < 0.05). The supra-marginal gyrus, mid-part of the precentral sulcus, angular gyrus in the left hemisphere, bilateral sensorimotor areas for legs, and bilateral isthmus-cingulate areas showed larger z-scores in patients with extra-territorial pain than in patients without the pain (p < 0.05).

CONCLUSIONS

The static and moving two-point discrimination sensations signify the ability of tactile spatial acuity. Bilateral sensorimotor areas were activated in sites that were not the hand. Furthermore, the inferior parietal lobule in the left hemisphere, which synthesizes and integrates multiple sensations showed high activation. Our findings suggested that the mechanism of extra-territorial pain was associated with dysfunction of spatial cognition.

Altered sensorimotor representations after recovery from peripheral nerve damage in neuralgic amyotrophy

Neuralgic amyotrophy is a common peripheral nerve disorder caused by acute autoimmune inflammation of the brachial plexus. Subsequent weakness of the stabilizing shoulder muscles leads to compensatory strategies and abnormal motor control of the shoulder. Despite recovery of peripheral nerves and muscle strength over time, motor dysfunction often persists. Suboptimal motor recovery has been linked to maladaptive changes in the central motor system in several nervous system disorders. We therefore hypothesized that neuralgic amyotrophy patients with persistent motor dysfunction may have altered cerebral sensorimotor representations of the affected upper limb. To test this hypothesis, 21 neuralgic amyotrophy patients (mean age 45 ± 12 years, 5 female) with persistent lateralized symptoms in the right upper limb and 20 age- and sex-matched healthy controls, all right-handed, performed a hand laterality judgement task in a cross-sectional comparison. Previous evidence has shown that to solve this task, subjects rely on sensorimotor representations of their own upper limb, using a first-person imagery perspective without actual motor execution. This enabled us to investigate altered central sensorimotor representations while controlling for altered motor output and altered somatosensory afference. We found that neuralgic amyotrophy patients were specifically less accurate for laterality judgments of their affected right limb, as compared to healthy controls. There were no significant group differences in reaction times. Both groups used a first-person imagery perspective, as evidenced by changes in reaction times as a function of participants' own arm posture. We conclude that cerebral sensorimotor representations of the affected upper limb are altered in neuralgic amyotrophy patients. This suggests that maladaptive central neuroplasticity may occur in response to peripheral nerve damage, thereby contributing to motor dysfunction. Therapies focused on altering cerebral sensorimotor representations may help to treat peripheral nerve disorders such as neuralgic amyotrophy.

A magnetoencephalographic study of longitudinal brain function alterations following carpal tunnel release

We investigate changes in brain function before and after carpal tunnel release. Magnetoencephalography (MEG), during which we recorded somatosensory evoked cortical magnetic fields (SEFs), and a clinical evaluation were performed before surgery and 6 months after. The distance on the vertical axis between the equivalent current dipoles (ECDs) for the first and third digits before surgery was significantly less than after surgery. There were no significant differences in values between the control participant and patients after surgery. In terms of distal motor latency, there was a negative correlation with the distance. The recovery function of the root mean square (RMS) before surgery for the N20m was less suppressed at 10 ms of ISI in patients, compared to controls. There were no significant differences in the RMS values for patients before and after surgery. Our results indicate that treating peripheral nerve lesions, such as in carpal tunnel release, positively modifies brain function.

Cortical Thickness Alterations in Chronic Pain Disorder: An Exploratory MRI Study

OBJECTIVE

Chronic pain disorder (CPD) has been associated with brain changes, especially in limbic circuits. However, in most patients with chronic pain, depression or anxiety is a common comorbidity. In this exploratory and naturalistic study, we investigated brain cortical thickness (CTh) differences between patients with CPD and healthy controls, with consideration of concurrent psychiatric symptoms.

METHODS

Twenty-three patients with CPD and 23 age- and sex-matched healthy volunteers were included in this study. CTh was estimated using Freesurfer on high-resolution three-dimensional T1-weighted images acquired with a 3T scanner. Group differences were investigated using an analysis of covariance model that included age, sex, and Beck Depression Inventory I and Trait Anxiety Inventory scores as covariates. The relationship between CTh and Toronto Alexithymia Scale (TAS-20) scores was also investigated in patients. Data were corrected for multiplicity using the False Discovery Rate approach (q < .05).

RESULTS

The comparison between groups using demographics and Beck Depression Inventory I scores as covariates showed thinner cortex in patients compared with controls, after correction for multiplicity in the left precentral (F(1,42) = 21.9, p < .05) and postcentral gyri (F(1,42) = 26.9, p < .05) and in the left inferior temporal sulcus (F(1,42) = 19.6, p < .05). Moreover, using the Trait Anxiety Inventory as covariate, a trend toward significance (p < .001 uncorrected) was seen for the left precentral gyrus (F(1,42) = 13.8), right middle frontal (F(1,42) = 14.3) and inferior parietal gyri (F(1,42) = 13.4), and right anterior temporal pole (F(1,42) = 15.9).

CONCLUSIONS

The results indicate that brain morphological differences between patients with chronic pain disorder and healthy controls are localized to regions that correspond to sensory as well as affective dimensions of pain processing.

A Longitudinal fMRI Research on Neural Plasticity and Sensory Outcome of Carpal Tunnel Syndrome

Peripheral nerve compression is reported to induce cortical plasticity, which was well pictured by former researches. However, the longitudinal changes brought by surgical treatment are not clear. In this research, 18 subjects who suffered from bilateral carpal tunnel syndrome were evaluated using task-dependent fMRI and electromyography assessment before and after surgery. The third digit was tactually simulated by von Frey filaments. The results demonstrated that the pattern of activation was similar but a decreased extent of activation in the postcentral gyrus, inferior frontal lobe, superior frontal lobe, and parahippocampal gyrus after surgery was found. The correlation analysis showed a significant correlation between the decreased number of activated voxels and the improvement of EMG performance. This result implied a potential connection between fMRI measurement and clinical improvement.

Brain remodeling after chronic median nerve compression in a rat model

Carpal tunnel syndrome is the most common compressive neuropathy, presenting with sensorimotor dysfunction. In carpal tunnel syndrome patients, irregular afferent signals on functional magnetic resonance imaging are associated with changes in neural plasticity during peripheral nerve injury. However, it is difficult to obtain multi-point neuroimaging data of the brain in the clinic. In the present study, a rat model of median nerve compression was established by median nerve ligation, i.e., carpal tunnel syndrome model. Sensory cortex remodeling was determined by functional magnetic resonance imaging between normal rats and carpal tunnel syndrome models at 2 weeks and 2 months after operation. Stimulation of bilateral paws by electricity for 30 seconds, alternating with 30 seconds of rest period (repeatedly 3 times), resulted in activation of the contralateral sensorimotor cortex in normal rats. When carpal tunnel syndrome rats received this stimulation, the contralateral cerebral hemisphere was markedly activated at 2 weeks after operation, including the primary motor cortex, cerebellum, and thalamus. Moreover, this activation was not visible at 2 months after operation. These findings suggest that significant remodeling of the cerebral cortex appears at 2 weeks and 2 months after median nerve compression.

Rewiring the primary somatosensory cortex in carpal tunnel syndrome with acupuncture

Carpal tunnel syndrome is the most common entrapment neuropathy, affecting the median nerve at the wrist. Acupuncture is a minimally-invasive and conservative therapeutic option, and while rooted in a complex practice ritual, acupuncture overlaps significantly with many conventional peripherally-focused neuromodulatory therapies. However, the neurophysiological mechanisms by which acupuncture impacts accepted subjective/psychological and objective/physiological outcomes are not well understood. Eligible patients (n = 80, 65 female, age: 49.3 ± 8.6 years) were enrolled and randomized into three intervention arms: (i) verum electro-acupuncture 'local' to the more affected hand; (ii) verum electro-acupuncture at 'distal' body sites, near the ankle contralesional to the more affected hand; and (iii) local sham electro-acupuncture using non-penetrating placebo needles. Acupuncture therapy was provided for 16 sessions over 8 weeks. Boston Carpal Tunnel Syndrome Questionnaire assessed pain and paraesthesia symptoms at baseline, following therapy and at 3-month follow-up. Nerve conduction studies assessing median nerve sensory latency and brain imaging data were acquired at baseline and following therapy. Functional magnetic resonance imaging assessed somatotopy in the primary somatosensory cortex using vibrotactile stimulation over three digits (2, 3 and 5). While all three acupuncture interventions reduced symptom severity, verum (local and distal) acupuncture was superior to sham in producing improvements in neurophysiological outcomes, both local to the wrist (i.e. median sensory nerve conduction latency) and in the brain (i.e. digit 2/3 cortical separation distance). Moreover, greater improvement in second/third interdigit cortical separation distance following verum acupuncture predicted sustained improvements in symptom severity at 3-month follow-up. We further explored potential differential mechanisms of local versus distal acupuncture using diffusion tensor imaging of white matter microstructure adjacent to the primary somatosensory cortex. Compared to healthy adults (n = 34, 28 female, 49.7 ± 9.9 years old), patients with carpal tunnel syndrome demonstrated increased fractional anisotropy in several regions and, for these regions we found that improvement in median nerve latency was associated with reduction of fractional anisotropy near (i) contralesional hand area following verum, but not sham, acupuncture; (ii) ipsilesional hand area following local, but not distal or sham, acupuncture; and (iii) ipsilesional leg area following distal, but not local or sham, acupuncture. As these primary somatosensory cortex subregions are distinctly targeted by local versus distal acupuncture electrostimulation, acupuncture at local versus distal sites may improve median nerve function at the wrist by somatotopically distinct neuroplasticity in the primary somatosensory cortex following therapy. Our study further suggests that improvements in primary somatosensory cortex somatotopy can predict long-term clinical outcomes for carpal tunnel syndrome.

Carpal tunnel syndrome impairs index finger responses to unpredictable perturbations

The fine-tuning of digit forces to object properties can be disrupted by carpal tunnel syndrome (CTS). CTS' effects on hand function have mainly been investigated using predictable manipulation tasks; however, unpredictable perturbations are commonly encountered during manual tasks, presenting situations which may be more challenging to CTS patients given their hand impairments. The purpose of this study was to investigate muscle and force responses of the index finger to unpredictable perturbations in patients with CTS. Nine CTS patients and nine asymptomatic controls were instructed to stop the movement of a sliding plate by increasing index finger force following an unexpected perturbation. The electrical activity of the first dorsal interosseous muscle and forces exerted by the index finger were recorded. CTS patients demonstrated 20.9% greater muscle response latency and 12.0% greater force response latency compared to controls (p<0.05). The duration of plate sliding was significantly different between groups (p<0.05); the CTS group's duration was 142.2±5.8ms compared to the control group's duration of 133.1±8.4ms. Although CTS patients had increased muscle and force response durations comparatively, these differences were not statistically significant. Findings from this study suggest CTS-induced sensorimotor deficits interfere with accurate detection, processing and response to unpredictable perturbations. These deficits could be accounted for at multiple levels of the peripheral and central nervous systems. Delayed and decreased responses may indicate inefficient object manipulation by CTS patients and may help to explain why CTS patients tend to drop objects.

[An effect of ipidacrine (neuromidin) on electroneuromyographic parameters in the conditions of artificial decompression (a clinical/instrumental study)]

AIM

To study an effect of neuromidin on the changes in electroneuromyographic (ENMG) parameters in patients with carpal tunnel syndrome in the conditions of artificial decompression of a forearm.

MATERIAL AND METHODS

Sixty-four 64 patients, 46 women and 18 men, mean age 50,7±4,5years, matched for disease severity were studied. The patients were randomized into neuromidin group and control group. Neuromidin was introduced using subcutaneous local perineural injections. Characteristics of neuromidin effect on the changes in ENMG parameters of the median nerve were studied in a model of additional artificial decompression of the median nerve.

RESULTS AND CONCLUSION

There was the significant depression of the nerve function and worsening of ENMG parameters during the additional decompression as well as the aggravation of conduction block along nerve fibers (motor and sensory). In patients treated with ipidacrine, there was an increase in the amplitude of sensory and (to a less extent) of M-response that indicated the activation of axonal transport and reservation of functioning of the compressed nerve.