The relationship of nerve fibre pathology to sensory function in entrapment neuropathy

Inflammatory cytokines and carpal tunnel syndrome: A causal relationship revealed

OBJECTIVES

Carpal tunnel syndrome (CTS) and certain inflammatory cytokines have been linked in observational studies; however, the exact causative linkages remain unknown. The purpose of this study is to investigate any possible link between the onset of CTS and 91 inflammatory cytokines.

METHODS

A two-sample bidirectional Mendelian randomization (MR) approach was used in this investigation. 91 circulating inflammatory cytokines' genetic variants were retrieved from the European ancestry genome-wide association study (GWAS) database. From germline GWAS, summary data for 24,766 CTS patients and 360,538 controls were gathered. The instrumental variables were single nucleotide polymorphisms (SNPs) that were highly correlated with the 91 inflammatory cytokines. The random-effects inverse-variance weighted (IVW) approach was employed in the primary analysis, and multiple comparisons were subjected to the Bonferroni correction. Sensitivity analysis was performed to evaluate the validity of the causal relationship.

RESULTS

Our findings showed a negative correlation between CCL19, FGF-19, IL-5, TGF-alpha, TRAIL, and the risk of CTS. Specifically, CCL19 (odds ratio [OR]: 0.944, 95 % confidence interval [CI]: 0.894-0.996, p = 0.0349), FGF-19 (OR: 0.940, 95 % CI: 0.894-0.987, p = 0.0133), IL-5 (OR: 0.936, 95 % CI: 0.885-0.990, p = 0.0212), TGF-alpha (OR: 0.902, 95 % CI: 0.838-0.970, p = 0.0057), and TRAIL (OR: 0.926, 95 % CI: 0.881-0.974, p = 0.0026) were inversely related to CTS risk. Conversely, CCL20, IL-2RB, and IL-6 were positively associated with an increased risk of CTS. Specifically, CCL20 (OR: 1.072, 95 % CI: 1.005-1.142, p = 0.0334), IL-2RB (OR: 1.067, 95 % CI: 1.001-1.137, p = 0.0463), and IL-6 (OR: 1.088, 95 % CI: 1.005-1.177, p = 0.0365) were positively correlated with CTS risk. Reverse Mendelian randomization analyses indicated no evidence of a reverse causal relationship between CTS and inflammatory cytokines.

CONCLUSION

According to this study, there is a causal link between CTS and certain inflammatory cytokines, which suggests that these cytokines may be important in the pathophysiology of CTS. To confirm these results and investigate the specific function of these cytokines in the beginning and development of CTS, more investigation is necessary.

Mechanisms of neurodynamic treatments (MONET): a protocol for a mechanistic, randomised, single-blind controlled trial in patients with carpal tunnel syndrome

BACKGROUND

Physiotherapeutic management is the first-line intervention for patients with entrapment neuropathies such as carpal tunnel syndrome (CTS). As part of physiotherapy, neurodynamic interventions are often used to treat people with peripheral nerve involvement, but their mechanisms of action are yet to be fully understood. The MONET (mechanisms of neurodynamic treatment) study aims to investigate the mechanisms of action of neurodynamic exercise intervention on nerve structure, and function.

METHODS

This mechanistic, randomised, single-blind, controlled trial will include 78 people with electrodiagnostically confirmed mild or moderate CTS and 30 healthy participants (N = 108). Patients will be randomly assigned into (1) a 6-week progressive home-based neurodynamic exercise intervention (n = 26), (2) a steroid injection (= 26), or (3) advice (n = 26) group. The primary outcome measure is fractional anisotropy of the median nerve at the wrist using advanced magnetic resonance neuroimaging. Secondary outcome measures include neuroimaging markers at the wrist, quantitative sensory testing, electrodiagnostics, and patient reported outcome measures. Exploratory outcomes include neuroimaging markers at the cervical spine, inflammatory and axonal integrity markers in serial blood samples and biopsies of median nerve innervated skin. We will evaluate outcome measures at baseline and at the end of the 6-week intervention period. We will repeat questionnaires at 6-months. Two-way repeated measures ANCOVAs, followed by posthoc testing will be performed to identify differences in outcome measures among groups and over time.

DISCUSSION

This study will advance our understanding of the mechanisms of action underpinning neurodynamic exercises, which will ultimately help clinicians to better target these treatments to those patients who may benefit from them. The inclusion of a positive control group (steroid injection) and a negative control group (advice) will strengthen the interpretation of our results.

TRIAL REGISTRATION

NCT05859412, 20/4/2023.

Conservative Management of Occipital Neuralgia Supported by Physical Therapy: A Review of Available Research and Mechanistic Rationale to Guide Treatment

PURPOSE OF REVIEW

Conservative management is consistently recommended as a first line intervention for occipital neuralgia (ON); however, there is limited clinical research regarding conservative intervention for ON. This lack of research may lead to underutilization or unwarranted variability in conservative treatment. This article provides mechanism-based guidance for conservative management of ON as a component of a multimodal treatment approach, and discusses the role of the physical therapist in the care team. It also highlights opportunities for further research to refine conservative management of this condition.

RECENT FINDINGS

Published research on conservative interventions specific to ON is limited to very low-quality evidence for the use of TENS. The contemporary shift toward precision pain management emphasizing treatment based on a patient's constellation of clinical features-a phenotype-rather than solely a diagnosis provides more personalized and specifically targeted pain treatment. This paradigm can guide treatment in cases where diagnosis-specific research is lacking and can be used to inform conservative treatment in this case. Various conservative interventions have demonstrated efficacy in treating many of the symptoms and accepted etiologies of ON. Conservative interventions provided by a physical therapist including exercise, manual therapy, posture and biomechanical training, TENS, patient education, and desensitization have mechanistic justification to treat symptoms and causes of ON. Physical therapists have adequate time and skill to provide such progressive and iterative interventions and should be included in a multimodal treatment plan for ON. Further research is required to determine appropriate dosing, sequencing, and progression of conservative treatments.

Systemic low-grade C-reactive protein is associated with proximal symptom spread in carpal tunnel syndrome

Introduction

Neuropathic pain is a highly prevalent condition associated with persistent disability. Some patients with neuropathic pain experience symptom spread outside neuroanatomical boundaries; these patients report more severe sensory symptoms and greater disability. However, the mechanisms behind such symptom spread are not fully understood.

Objective

We used pre-surgical carpal tunnel syndrome (CTS) as a human model system of neuropathic pain to identify differences in the concentration of serologic inflammatory mediators between patients with CTS with territorial symptoms and those with proximal symptom spread to either the elbow or shoulder/neck.

Methods

We performed a post-hoc analysis, comparing levels of serologic inflammatory mediators in a discovery cohort among 3 symptoms spread profiles (n = 55; n = 25 no spread, n = 21 spread to elbow, n = 9 spread to shoulder/neck). We then de-novo analysed the significantly dysregulated mediators in an independent validation cohort (n = 72; n = 34 no spread, n = 16 spread to elbow, n = 22 spread to shoulder/neck).

Results

The discovery cohort revealed higher serum concentrations of C-reactive protein (CRP) and interleukin-6 in patients with any symptom spread proximal to the wrist; interferon-γ was higher in patients with symptom spread to the elbow compared with those without proximal spread. The validation study replicated the association of higher CRP concentrations in patients with proximal spread to the elbow (no spread: median [interquartile range] 2.5 [5.4]; spread to elbow 6.2 [4.6]; spread to shoulder/neck 2.6 [3.7], P = 0.006). No other markers replicated in the validation cohort.

Conclusions

Our findings suggest that proximal symptom spread in the context of neuropathic symptoms is associated with low-grade inflammation.

Higher densities of T-lymphocytes in the subsynovial connective tissue of people with carpal tunnel syndrome

Symptoms in people with carpal tunnel syndrome (CTS) are traditionally attributed to neural tissue, but recent studies suggest that the subsynovial connective tissue (SSCT) may also play a role in CTS. The SSCT undergoes fibrotic thickening which is generally described as "non-inflammatory" based on basic histology. This study uses immunohistochemistry to determine the presence of macrophages and T-cells within SSCT and their relationship with symptoms in people with CTS. SSCT was collected from twenty people with CTS and eight controls undergoing wrist fracture surgery. Immunohistochemical quantification of CD3+ T-cells and CD68+ macrophage densities as well as CD4+/CD8+ T-cell subpopulations were compared between groups using independent t-tests. Spearman correlations were used to identify associations between immune cell densities and CTS symptom scores. The density of CD3+ T-cells was significantly higher in SSCT of people with CTS compared to controls (CTS mean 26.7 (SD 13.7); controls 6.78 (6.3), p = 0.0005) while the density of CD68+ macrophages was lower (CTS mean 9.5 (SD 6.0); controls 17.7 (8.2), p = 0.0058). Neither CD68+ nor CD3+ cell densities correlated with symptom scores. In contrast to previous assumptions, our data show that the SSCT in the carpal tunnel in both people with CTS and controls is not devoid of immune cells. Whereas the higher density of CD68+ macrophages in control participants may be associated with their early recruitment after acute fracture, CD3+ cells within the SSCT may play a role in chronic CTS.

Central Sensitization in Patients with Chronic Pain Secondary to Carpal Tunnel Syndrome and Determinants

Purpose

Central sensitization (CS) is commonly seen in chronic pain disorders, including neuropathic pain. However, there exist inconsistencies concerning the presence of CS in chronic pain secondary to carpal tunnel syndrome (CTS). CS and neuropathic pain manifestations in CTS remain not well established. Therefore, this study aims to investigate the CS and pain profiles in patients with CTS and to explore the potential determinants associated with CS.

Patients and Methods

Patients with suspected CTS symptoms lasting 3 months or above and healthy controls were enrolled. History, physical examinations, and nerve conduction studies were employed to confirm the diagnosis and severity of median nerve dysfunction. The central sensitization inventory (CSI) was used to screen CS. Other outcomes included neuropathic pain, CTS-specific symptom severity and functions, emotion, and health-related quality of life. Between-group comparisons were conducted in terms of the CS presence. Logistic regression analysis was performed to identify determinants associated with CS.

Results

Over 60% of participants with CTS were found with clinical CS, significantly higher than that in the control group. More than 70% of the CTS participants were identified to have possible or very likely neuropathic pain components. In addition, one-fourth of CTS cases had depression or anxiety. Anxiety was associated with an increased risk of developing CS in CTS (adjusted OR=1.31, 95% CI 1.08-1.59), whereas higher self-perceived general health rating was negatively associated with the presence of CS (adjusted OR=0.92, 95% CI 0.88-0.97) in the multivariate adjusted regression model.

Conclusion

CS is prevalent in patients with CTS. Predominant neuropathic pain characteristics were uncovered in CTS patients as well as comorbid psychological distress. Significant association was found between anxiety and CS presence. Self-perceived general health was inversely related to CS. Further research is warranted to explore the mechanisms of anxiety and central pain processing in painful entrapment neuropathy.

The effectiveness of mobilization with movement on patients with mild and moderate carpal tunnel syndrome: A single-blinded, randomized controlled study

STUDY DESIGN

Single-blinded, randomized controlled study.

INTRODUCTION

Carpal Tunnel Syndrome (CTS) causes pain and loss of function in the affected hand. The mobilization with movement (MWM) technique is a manual therapy method applied to correct joint movement limitation and to relieve pain and functional disorders.

PURPOSE OF THE STUDY

This study aimed to examine the effectiveness of MWM technique on pain, grip strength, range of motion, edema, hand reaction, nerve conduction, and functional status in patients with CTS.

METHODS

A total of 45 patients enrolled in the study. The MWM group (n = 18) completed a 4-week combined conservative physiotherapy and MWM program, whereas the control group (n = 18) received only the 4 weeks of conservative physiotherapy. Pain severity according to the numerical rating scale was used as primary outcome.

RESULTS

We found an improvement within the subjects in resting pain (MWMG:5.1 ± 3.6 vs 1.1 ± 2.4, Effect Size (ES)=1.3; CG:4.5 ± 3.3 vs 1.0 ± 2.2, ES=1.1), in activity pain (MWMG:6.5 ± 3.7 vs 1.1 ± 2.4, ES=1.5; CG:4.8 ± 3.4 vs 2.2 ± 2.3, ES=1) and in night pain (MWMG:5.9 ± 3.2 vs 1.8 ± 2.5, ES=1.2; CG:5.3 ± 4.2 vs ± 2.3 ± 3.5, ES=0.9). For between the groups, a statistical difference was found for the activity pain, Disabilities of the Arm Shoulder and Hand Questionnaire score (MWMG:52.2 ± 23.8 vs 27 ± 24.7, ES=1.3; CG:47.0 ± 24.8 vs 41.5 ± 22.1, ES=0.2), Michigan Hand Outcomes Questionnaire (MHQ-1), (MWMG:44.4 ± 23.7 vs 74.7 ± 24.5, ES=1.3; CG:44.8 ± 17.4 vs 57.4 ± 21.7, ES=0.9) and MHQ-5 (MWMG:68.8 ± 13.1 vs 82.5 ± 11.5, ES=0.9; CG:63.4 ± 26.7 vs 59.3 ± 25.8, ES=0.1) parameters in favour of MWM group.

DISCUSSION

This study showed that MWM compared to conservative physiotherapy might be more effective in reducing perceived symptoms in mild and moderate CTS patients.

CONCLUSIONS

MWM produced a small benefit to recovery of activity pain and upper extremity functionality level outcomes of patients with mild to moderate CTS when added to a traditional CTS physical therapy program.

Integrating jigsaw puzzle thinking into practice: the assessment of cervical spine radiculopathy

PURPOSE OF REVIEW

Cervical spine radiculopathy (CSR) presents a complex socioeconomic problem for patients, clinicians, families, employers and healthcare systems. Due to the heterogeneity of clinical presentation and underlying mechanisms, clinical assessment can be challenging. This review will examine the literature on the underlying pathophysiology and studies investigating the holistic assessment strategies for this disabling condition. The authors will focus particular attention on the psychological factors associated with CSR and the physical and imaging strategies to establish a diagnosis.

RECENT FINDINGS

Contemporary CSR assessment should identify the underlying pathomechanisms and how this may impact the somatosensory nervous system integrity and function. No physical assessment test in isolation will establish CSR diagnosis; therefore, clinicians should utilise a cluster of tests and recognise the potential limitations as part of a clinical reasoning framework. The assessment of the somatosensory nervous system can provide insights into particular subgroups of CSR presentation, which may provide interesting opportunities to continue to enhance individualised assessment and management strategies for CSR. The interplay between psychological factors can influence the diagnosis and recovery times for a person with CSR, and clinicians should continue to explore how these factors may influence a person's prognosis. The authors will discuss the opportunities for future research and limitations of contemporary approaches to assessment, underpinned by evidence, and how this supports a clinical assessment to establish CSR diagnosis.

SUMMARY

Research should continue to investigate how clinicians assess the interplay between physical and psychological factors to inform the establishment of CSR. Specifically, there is a need to investigate the validity and reliability of combining somatosensory, motor and imaging assessment findings to reach a diagnosis and inform onward management plans.

The effectiveness of photobiomodulation therapy on inferior alveolar nerve injury: A systematic review and META-analysis

OBJECTIVE

The aim of this META-analysis was to evaluate the efficacy of photobiomodulation (PBM) therapy in the treatment of inferior alveolar nerve (IAN) injury due to orthognathic surgeries, extraction of impacted third molars and mandibular fractures.

METHODS AND MATERIALS

A electric search was conducted by a combination of manual search and four electric databases including Pubmed, Embase, Cochrane library and Web of Science, with no limitation on language and publication date. Gray literature was searched in ClinicalTrials.gov and googlescholar. All retrieved articles were imported into ENDNOTE software (version X9) and screened by two independent reviewers. All analysis was performed using the REVMAN software (version 5.3).

RESULTS

Finally, 15 randomized controlled trials met the inclusion criteria for qualitative analysis and 14 for META-analysis from 219 articles. The results showed that PBM therapy had no effect on nerve injury in a short period of time (0-48h, 14 days), but had significant effect over 30 days. However, the effect of photobiomodulation therapy on thermal discrimination was still controversial, most authors supported no significant improvement. By calculating the effective rate of PBM, it was found that there was no significant difference in the onset time of treatment, whether within or over 6 months.

CONCLUSIONS

The results of this META-analysis show that PBM therapy is effective in the treatment of IAN injures no matter it begins early or later. However, due to the limited number of well-designed RCTs and small number of patients in each study, it would be necessary to conduct randomized controlled trials with large sample size, long follow-up time and more standardized treatment and evaluation methods in the future to provide more accurate and clinically meaningful results.

A comparative study on efficacy of modified endoscopic minimally invasive treatment and traditional open surgery for primary carpal tunnel syndrome

BACKGROUND AND OBJECTIVE

Carpal tunnel syndrome (CTS) is the most common type of median nerve entrapment neuropathy. This study aims to comparatively assess the effectiveness and clinical efficacy of modified transforaminal endoscopic minimally invasive incision of transverse carpal ligament against traditional open incision of transverse carpal ligament in the treatment of CTS.

METHOD

The clinical data of 35 patients (57 wrists) with primary CTS treated in Shanxi Bethune Hospital, China, were retrospectively analyzed. The patients were divided into observation group (21 cases, 33 wrists) and control group (14 cases, 24 wrists), respectively, who underwent modified endoscopic minimally invasive incision of transverse carpal ligament and traditional open incision of transverse carpal ligament release. The Boston Carpal Tunnel Questionnaire (BCTQ) was assessed at for points: before the operation; 2 weeks; 1 month; and 3 months after operation. The BCTQ scores of the two groups were compared on all four points. The incidence of intraoperative and postoperative complication was used as the evaluation index. The study variables were comparatively assessed before and postoperation and also between the groups.

RESULTS

The BCTQ scores at 2 weeks, 1 month and 3 months after the operation were significantly lower than preoperative BCTQ scores (P < 0.005) for both the groups. There was no significant difference in BCTQ scores between the two groups at the four assessment points (P > 0.005). The scar size and wound healing time were significantly better with modified transforaminal endoscopic minimally invasive transverse carpal ligament incision.

CONCLUSION

The clinical effects of both modified transforaminal minimally invasive incision of transverse carpal ligament and traditional open incision of transverse carpal ligament are significant, while the treatment efficacy of modified transforaminal minimally invasive transverse carpal ligament incision is better in terms of operation time, wound size, postoperative scar size and incision healing time.

Supraorbital Nerve Stimulation for Facial Pain

PURPOSE OF REVIEW

Chronic facial pain is considered one of the conditions that affect quality of daily life of patients significantly and makes them seek medical help. Intractable facial pain with failed trials of medical treatment and other pain management therapies presents a challenge for neurologists, pain specialists, and neurosurgeons. We describe the possibility of proposing peripheral nerve stimulation of the supraorbital nerves to treat patients with medically intractable facial pain. Stimulation of the supraorbital nerves is performed using percutaneously inserted electrodes that are positioned in the epi-fascial plane, traversing the course of the supraorbital nerves. The procedure has two phases starting with a trial by temporary electrodes that are inserted under fluoroscopic guidance and are anchored to the skin. This trial usually lasts for a few days to 2 weeks. If successful, we proceed to the insertion of a permanent electrode that is tunneled under the skin behind the ear toward the infraclavicular region in which we make a pocket for the implantable pulse generator.

RECENT FINDINGS

This procedure has been used in multiple patients with promising results which was published in literature. Literature shows that it provides relief of medically intractable pain, without the need for destructive procedures or more central modulation approaches with a preferable safety profile compared to other invasive procedures. Supraorbital nerve stimulation is now considered a valid modality of treatment for patients with medically intractable facial pain and can be offered as a reliable alternative for the patients while discussing the proper plan of management.

Chronic pain and local pain in usually painless conditions including neuroma may be due to compressive proximal neural lesion

It has been unexplained why chronic pain does not invariably accompany chronic pain-prone disorders. This question-driven, hypothesis-based article suggests that the reason may be varying occurrence of concomitant peripheral compressive proximal neural lesion (cPNL), e.g., radiculopathy and entrapment plexopathies. Transition of acute to chronic pain may involve development or aggravation of cPNL. Nociceptive hypersensitivity induced and/or maintained by cPNL may be responsible for all types of general chronic pain as well as for pain in isolated tissue conditions that are usually painless, e.g., neuroma, scar, and Dupuytren's fibromatosis. Compressive PNL induces focal neuroinflammation, which can maintain dorsal root ganglion neuron (DRGn) hyperexcitability (i.e., peripheral sensitization) and thus fuel central sensitization (i.e., hyperexcitability of central nociceptive pathways) and a vicious cycle of chronic pain. DRGn hyperexcitability and cPNL may reciprocally maintain each other, because cPNL can result from reflexive myospasm-induced myofascial tension, muscle weakness, and consequent muscle imbalance- and/or pain-provoked compensatory overuse. Because of pain and motor fiber damage, cPNL can worsen the causative musculoskeletal dysfunction, which further accounts for the reciprocity between the latter two factors. Sensitization increases nerve vulnerability and thus catalyzes this cycle. Because of these mechanisms and relatively greater number of neurons involved, cPNL is more likely to maintain DRGn hyperexcitability in comparison to distal neural and non-neural lesions. Compressive PNL is associated with restricted neural mobility. Intermittent (dynamic) nature of cPNL may be essential in chronic pain, because healed (i.e., fibrotic) lesions are physiologically silent and, consequently, cannot provide nociceptive input. Not all patients may be equally susceptible to develop cPNL, because occurrence of cPNL may vary as vary patients' predisposition to musculoskeletal impairment. Sensitization is accompanied by pressure pain threshold decrease and consequent mechanical allodynia and hyperalgesia, which can cause unusual local pain via natural pressure exerted by space occupying lesions or by their examination. Worsening of local pain is similarly explainable. Neuroma pain may be due to cPNL-induced axonal mechanical sensitivity and hypersensitivity of the nociceptive nervi nervorum of the nerve trunk and its stump. Intermittence and symptomatic complexity of cPNL may be the cause of frequent misdiagnosis of chronic pain.

Prevalence of carpal tunnel syndrome in patients with long-term type 2 diabetes mellitus

Generally, Carpal tunnel syndrome (CTS) is more common in diabetes mellitus (DM), especially in subjects with coexisting diabetic polyneuropathy (DPN) and/or long-term DM. Based on the analysis of nerve conduction velocity (NCV), the prevalence of CTS and the features of nerve injury were retrospectively explored in type 2 diabetes mellitus (T2DM) patients. In this cohort, there were 353 T2DM patients who were hospitalized in Taiyuan Central Hospitalbetween January 2018 and January 2019. The pathological rates of NCVs between the left and right median nerves were compared, including the gender effect. The examinations were mainly directed to analyze the median nerve injury features. Among 353 patients, 139 patients (39.3%) presented with CTS. These 139 T2DM patients with CTS were then divided into groups based on the nerve injury location and injured nerve type. The prevalence of sensory nerve injury (SNI) was higher than that of motor nerve injury (MNI). The CTS patients had a significantly higher occurrence rate of SNI than MNI (P < 0.05). The abnormal rate of sensory nerve conduction velocity (SCV, P = 0.01) and motor nerve conduction velocity (MCV, P < 0.05) were higher in the right median nerve. No significant differences were detected for other nerves on either side. Significant differences in abnormal rates of SCV of the left (P = 0.04) and the right (P = 0.03) median nerves between the two genders were found. There were no significant abnormalities for other nerves on either side and either gender. Early screening of NCV is needed for T2DM patients to detect CTS with a high prevalence rate. This study suggests that early detection of NCV can identify CTS in the absence of clinical conditions and SNI may occur earlier in long-term T2DM patients with CTS.

Does peripheral neuroinflammation predict chronicity following whiplash injury? Protocol for a prospective cohort study

INTRODUCTION

Whiplash-associated disorder grade 2 (WAD2) is characterised by musculoskeletal pain/tenderness but no apparent nerve injury. However, studies have found clinical features indicative of neuropathy and neuropathic pain. These studies may indicate peripheral nerve inflammation, since preclinical neuritis models found mechanical sensitivity in inflamed, intact nociceptors. The primary aim of this study is to establish the contribution of peripheral neuroinflammation to WAD2 and its role in prognosis. Participants will be invited to participate in a sub-study investigating the contribution of cutaneous small fibre pathology to WAD2.

METHODS AND ANALYSIS

115 participants within 1 month following whiplash injury and 34 healthy control participants will be recruited and complete validated questionnaires for pain, function and psychological factors. Data collection will take place at the Universities of Sussex and Oxford, UK. Clinical examination, quantitative sensory testing and blood samples will be undertaken. MRI scans using T2-weighted and diffusion tensor images of the brachial plexus and wrist will determine nerve inflammation and nerve structural changes. Skin biopsies from a substudy will determine structural integrity of dermal and intraepidermal nerve fibres. At 6 months, we will evaluate recovery using Neck Disability Index and a self-rated global recovery question and repeat the outcome measures. Regression analysis will identify differences in MRI parameters, clinical tests and skin biopsies between participants with WAD2 and age/gender-matched controls. Linear and logistic regression analyses will assess if nerve inflammation (MRI parameters) predicts poor outcome. Mixed effects modelling will compare MRI and clinical measures between recovered and non-recovered participants over time.

ETHICS AND DISSEMINATION

Ethical approval was received from London-Brighton and Sussex Research Ethics Committee (20/PR/0625) and South Central-Oxford C Ethics Committee (18/SC/0263). Written informed consent will be obtained from participants prior to participation in the study. Results will be disseminated through publications in peer-reviewed journals, presentations at national/international conferences and social media.

TRIAL REGISTRATION NUMBER

NCT04940923.

[Quantitative sensory testing for neuropathic pain and its relevance for physiotherapy]

BACKGROUND

Neuropathic pain syndromes are typically characterized by high chronification rates as well as long and intensive pain episodes. Early and accurate diagnosis of neuropathic pain is a basic skill of physiotherapists and other medical professionals, may allow for appropriate medical treatment and help to prevent possible consequential damage. Quantitative sensory testing (QST) can be applied as a supplement to conventional neurological bedside testing in the evaluation of neuropathic pain. Over recent decades, QST has come to hold a significant position in the field of pain research. However, despite these developments, the application of QST in clinical practice has lagged behind.

OBJECTIVES

What is the value of QST in the study of neuropathic pain? Have the conditions for personal clinical use of the QST been established in physiotherapy practice? Have the pathways for specific implementation of the QST been defined?

METHOD

Literature research as part of a Bachelor thesis in Physiotherapy.

RESULTS

QST constitutes a valid examination tool that is able to evaluate the complete somatosensory profile. In this way, QST may provide substantial additional benefit in the examination of neuropathic pain patients compared to other conventional testing procedures, especially when it comes to small-fibre neuropathies. These small fibres seem to be particularly affected in asymptomatic patients as well as early phases of neuropathies and cannot be investigated via conventional testing procedures. This makes the use of partial aspects of the QST a proven instrument for physiotherapists and medical staff, which was particularly useful in the decision-making process for neuropathies.

DISCUSSION

Nonetheless, regarding the results, there are still several limiting factors that hamper the routine use of QST. Some of these can be resolved by precisely adhering to testing protocols and taking precautions. Other highly relevant issues for clinical practice, such as the immense cost of equipment and the excessive time required for testing, have not been satisfactorily overcome as yet. Less comprehensive testing protocols as well as the innovation of handy and cost-effective testing devices might offer initial approaches to enhance the widespread use of QST. Complementing conventional bedside testing by adding thermal discrimination tests and pain detection threshold tests might prove to be another possibility to integrate the benefit of QST into clinical practice.

CONCLUSION

QST makes a significant contribution to the investigation and diagnosis of neuropathies. Physiotherapists are encouraged to implement partial aspects of the QST in a standard examination in order to have a positive effect on both early detection and treatment.

Cutaneous expression of growth-associated protein 43 is not a compelling marker for human nerve regeneration in carpal tunnel syndrome

Growth-associated protein 43 (GAP-43) has long been used as a marker for nerve regeneration following nerve injury, with numerous in vitro and animal studies showing its upregulation in regenerating neurons. In humans, expression of GAP-43 has predominantly been examined in skin biopsies from patients with peripheral neuropathies; with several studies showing a reduction in GAP-43 immunoreactive cutaneous nerve fibres. However, it remains elusive whether cutaneous GAP-43 is a valid marker for human nerve regeneration. Here, we present a cohort of 22 patients with electrodiagnostically confirmed carpal tunnel syndrome (CTS), used as a model system for focal nerve injury and neural regeneration after decompression surgery. We evaluate GAP-43 immunoreactivity and RNA expression levels in finger skin biopsies taken before and 6 months after surgery, relative to healthy controls. We further classify patients as 'regenerators' or 'non-regenerators' based on post-surgical epidermal re-innervation. We demonstrate that patients with CTS have lower GAP-43 positive intra-epidermal nerve fibre density (IENFD) before surgery than healthy controls. However, this difference disappears when normalising for total IENFD. Of note, we found surgery did not change GAP-43 expression in IENF, with no differences both in patients who were classified as regenerators and non-regenerators. We also did not identify pre-post surgical differences in cutaneous GAP-43 gene expression or associations with regeneration. These findings suggest cutaneous GAP-43 may not be a compelling marker for nerve regeneration in humans.

Nerve pathology and neuropathic pain after whiplash injury: a systematic review and meta-analysis

ABSTRACT

There is no clear understanding of the mechanisms causing persistent pain in patients with whiplash-associated disorder (WAD). The aim of this systematic review was to assess the evidence for nerve pathology and neuropathic pain in patients with WAD. EMBASE, PubMed, CINAHL (EBSCO), and MEDLINE were searched from inception to September 1, 2020. Study quality and risk of bias were assessed using the Newcastle-Ottawa Quality Assessment Scales. Fifty-four studies reporting on 390,644 patients and 918 controls were included. Clinical questionnaires suggested symptoms of predominant neuropathic characteristic in 34% of patients (range 25%-75%). The mean prevalence of nerve pathology detected with neurological examination was 13% (0%-100%) and 32% (10%-100%) with electrodiagnostic testing. Patients independent of WAD severity (Quebec Task Force grades I-IV) demonstrated significantly impaired sensory detection thresholds of the index finger compared with controls, including mechanical (SMD 0.65 [0.30; 1.00] P < 0.005), current (SMD 0.82 [0.25; 1.39] P = 0.0165), cold (SMD -0.43 [-0.73; -0.13] P = 0.0204), and warm detection (SMD 0.84 [0.25; 1.42] P = 0.0200). Patients with WAD had significantly heightened nerve mechanosensitivity compared with controls on median nerve pressure pain thresholds (SMD -1.10 [-1.50; -0.70], P < 0.0001) and neurodynamic tests (SMD 1.68 [0.92; 2.44], P = 0.0004). Similar sensory dysfunction and nerve mechanosensitivity was seen in WAD grade II, which contradicts its traditional definition of absent nerve involvement. Our findings strongly suggest a subset of patients with WAD demonstrate signs of peripheral nerve pathology and neuropathic pain. Although there was heterogeneity among some studies, typical WAD classifications may need to be reconsidered and include detailed clinical assessments for nerve integrity.

Evaluation of Cold Sensitivity in Patients With Upper Extremity Nerve Compression Syndromes: A Scoping Review

PURPOSE

The aim of this study was to review the literature to determine the prevalence of cold sensitivity in upper extremity nerve compression syndromes and the impact of treating nerve compression syndromes on cold sensitivity.

METHODS

Following a standardized scoping review protocol, this study included interventional and observational study designs assessing patients with cold sensitivity and upper extremity nerve compression syndromes. Review articles, case reports, and small case series (n < 5) were excluded. The abstracts and eligible full texts were screened by 2 independent reviewers. Data were extracted and reported according to PRISMA extension for scoping reviews statement.

RESULTS

Three databases were searched (Ovid MEDLINE, Ovid EMBASE, and CINAHL on EBSCO); 274 references were reviewed. Fifteen studies from the database search and 8 studies from the reference search were eligible for this review (n = 23). Two interventional and 21 observational studies were identified. The most common method for assessing cold sensitivity was cold pain threshold testing (n = 12), followed by subjective patient reporting (n = 4). The Cold Intolerance Symptom Severity questionnaire was the most common validated patient-reported outcome questionnaire used in the studies (n = 3). Cold sensitivity was most commonly reported in carpal tunnel syndrome (96% of the studies). The prevalence of cold sensitivity in nerve compression syndromes ranged from 20% to 69%. Nerve decompression improved the severity of cold sensitivity in 5 of 6 studies where cold sensitivity was studied.

CONCLUSIONS

There is heterogenicity in the studies assessing cold sensitivity in nerve compression syndromes. Despite moderate prevalence in patients with carpal tunnel syndrome, cold sensitivity is understudied. Within the limitations of eligible studies reviewed, surgical decompression improved the severity of cold sensitivity in some studies.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

The Relevance of Collision Tests and Quantitative Sensory Testing in Diagnostics and Postoperative Outcome Prediction in Carpal Tunnel Syndrome

Background

The gold standards for the diagnosis and treatment of carpal tunnel syndrome (CTS) and its outcome are undecided. Using clinical and electrophysiological methods, we tried to establish which fibers achieved full postoperative recovery, and the possibility of using non-standard electrophysiological tests as outcome predictors.

Methods

The study group consisted of 35 patients and controls. The Historical–Objective Scale, standard neurography, conduction velocity distribution tests (CVD), and quantitative sensory testing (QST) were performed before and after CTS surgery.

Results

Clinical improvement was observed on average in 54.3% of the patients, higher in less advanced CTS. All parameters improved significantly after surgery, except for CVD; most remained worse than in the controls. Only QST parameters fully returned to normal limits. Patient age and CTS severity were important in the estimation of the risk of no improvement.

Conclusions

The efficiency of minimally invasive CTS surgery is higher in younger patients with less advanced CTS. Complete recovery was present only in small fibers; larger fibers could most likely be responsible for residual signs. We did not notice any benefits in CTS diagnosis using methods of small fiber assessment. QST seemed to be useful in the diagnosis of residual signs, and in deciding upon possible reoperation.

Which Psychological and Electrodiagnostic Factors Are Associated With Limb Disability in Patients With Carpal Tunnel Syndrome?

BACKGROUND

It has been observed that patients with carpal tunnel syndrome (CTS) who also experience emotional distress, depression, or anxiety report more severe symptoms. As patients' own perspectives about their health increasingly are guiding treatment decisions, it seems important to study the simultaneous association of psychological distress and neuropathology with hand disability in patients who have CTS, as this may help prioritize and sequence management steps.

QUESTIONS/PURPOSES

What are the relationships among validated scores for (1) depression, (2) anxiety, (3) pain catastrophizing, and (4) nerve electrodiagnostic severity with measures of hand disability in patients with confirmed CTS?

METHODS

Between 2017 and 2019, we evaluated 116 patients for CTS in a referral urban hospital in Mashhad, Iran. Of those, we considered 85% (99) as potentially eligible by considering the following Electromyography-Nerve Conduction Study (EMG-NCS) diagnostic criteria: sensory latency ≥ 3.5 Ms, median-ulnar latency difference ≥ 0.5 Ms, motor latency ≥ 4.2 Ms, and abnormal EMG findings in the opponens pollicis muscle (neurogenic motor unit action potentials, positive sharp waves, or fibrillation). A further 13% (15 of 116) were excluded because of nonidiopathic CTS and prior surgery, and another 12% (14 of 116) were lost because of incomplete datasets, leaving 60% (70 of 116) for final inclusion in this cross-sectional study. In all, 89% of patients were women with total mean age of 47 years. We measured depression and anxiety using the Hospital Anxiety and Depression Scale (HADS) questionnaire (scored from 0 to 21, with a minimum clinically important difference [MCID] of 1.7 points), and we evaluated patients' state of mind regarding pain using the Pain Catastrophizing Scale (PCS) (scored from 0 to 52). Higher scores on these questionnaires represent more distress and pain catastrophizing. Hand disability was assessed with Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) questionnaire outcomes (scored from 0 [no disability] to 100 [most severe disability]; MCID of 15 points), Likert pain score (from 0 to 10), and grip/pinch dynamometry results. Correlational analyses were conducted once among HADS and PCS scores and again among EMG-NCS indices with pain and disability variables to answer our first, third, and fourth questions, respectively. Regression analysis was performed to assess the percentage of variance in QuickDASH and pain severity, which could be explained by psychological and electrodiagnostic factors. We did not include grip and pinch in our multivariable model (regression analysis) as dependent variables because they did not correlate with any of psychological or EMG-NCS variables (all p values > 0.1). Significance was set at p < 0.05.

RESULTS

Correlational analysis showed that the scores of all three psychological questionnaires correlated with the QuickDASH score (r = 0.50, 0.42, and 0.53 for HADS-A, HADS-D, and PCS, respectively; p < 0.001 for all three), while EMG-NCS parameters had no correlation with QuickDASH and pain scores. We also found that 37% of the variance in QuickDASH score can be explained by HADS and PCS scores (r2 = 0.37; p < 0.001).

CONCLUSION

Evaluation and treatment of psychological distress before deciding on elective surgery for CTS is important because patient-reported disability-often used as a factor in surgical decision-making-is substantially correlated with emotional distress. Future prospective, controlled studies on this topic are recommended; ideally, these should evaluate psychological interventions specifically to ascertain whether they improve patients' ratings of hand disability.

LEVEL OF EVIDENCE

Level III, prognostic study.

Systemic inflammatory markers in neuropathic pain, nerve injury, and recovery

ABSTRACT

The role that inflammation plays in human nerve injury and neuropathic pain is incompletely understood. Previous studies highlight the role of inflammation in the generation and maintenance of neuropathic pain, but the emerging evidence from the preclinical literature for its role in the resolution of neuropathic pain remains to be explored in humans. Here, we use carpal tunnel syndrome (CTS) as a human model system of nerve injury and neuropathic pain to determine changes in serum cytokine protein levels and gene expression levels before (active stage of disease) and after carpal tunnel decompression surgery (recovery). Fifty-five patients with CTS were studied, and 21 healthy age-matched and gender-matched participants served as controls. In the active stage of the disease (CTS before surgery vs healthy controls), PTGES2 mRNA was decreased in patients (adjusted P = 0.013), while transforming growth factor-β and C-C motif chemokine ligand 5 protein levels were increased (adjusted P = 0.016 and P = 0.047, respectively). In the resolution phase (CTS before surgery vs after surgery), IL-9 mRNA was increased after surgery (adjusted P = 0.014) and expression of IL-6 mRNA and IL-4 protein levels were increased before surgery (adjusted P = 0.034 and P = 0.002, respectively). IL-9 mRNA expression negatively correlated with several (neuropathic) pain scores. By contrast, protein levels of IL-4 positively correlated with pain scores. In conclusion, we demonstrate specific dysregulation of systemic cytokine expression in both the active and resolution phases of nerve injury and neuropathic pain. IL-9 represents an interesting candidate associated with resolution of nerve injury and neuropathic pain.

Signs Indicative of Central Sensitization Are Present but Not Associated with the Central Sensitization Inventory in Patients with Focal Nerve Injury

Objective: Carpal tunnel syndrome (CTS) is the most common focal nerve injury. People with CTS may show alterations in central processing of nociceptive information. It remains unclear whether the central sensitization inventory (CSI) is capable of detecting such altered central pain processing. Methods: Thirty healthy volunteers were matched with 30 people with unilateral CTS from the orthopaedic waitlist. Changes to central pain processing were established through psychophysical sensory testing (bilateral pressure pain thresholds (PPT), conditioned pain modulation, temporal summation) and pain distribution on body charts. Patients also completed pain severity and function questionnaires, psychological questionnaires and the CSI. Results: Compared to healthy volunteers, patients with CTS have lower PPTs over the carpal tunnel bilaterally (t = −4.06, p < 0.0001 ipsilateral and t = −4.58, p < 0.0001 contralateral) and reduced conditioned pain modulation efficacy (t = −7.31, p <0.0001) but no differences in temporal summation (t = 0.52, p = 0.60). The CSI was not associated with psychophysical measures or pain distributions indicative of altered central pain processing. However, there was a correlation of the CSI with the Beck Depression Inventory (r = 0.426; p = 0.019). Conclusion: Patients with CTS show signs of altered central pain mechanisms. The CSI seems unsuitable to detect changes in central pain processing but is rather associated with psychological factors in people with focal nerve injuries.

Efficiency of 90-Min Extended EMLA-Induced Stimulated Skin-Wrinkling Test in the Diagnosis of Carpal Tunnel Syndrome

Background:

Previous researchers have used a 30-min eutectic mixture of local anesthetic (EMLA) test, which assesses the sympathetically mediated vasomotor function, in diagnosing carpal tunnel syndrome (CTS). However, its specificity was low, limiting its clinical diagnostic utility. In this study, we assessed the efficiency of 90-min extended EMLA-induced stimulated skin-wrinkling (SSW) test in CTS diagnosis.

Methods:

A cross-sectional study was designed among patients clinically diagnosed with CTS. Hands of healthy volunteers and the asymptomatic hands of selected patients served as control. The Boston symptom severity scale (SSS) and the neuropathic pain severity inventory (NPSI) were used to assess symptom severity, and nerve conduction study (NCS) was used to assess electrophysiological severity. EMLA-induced SSW was visually graded after 90 min of application and correlated with symptom and NCS severities.

Results:

Forty-two symptomatic hands and 30 asymptomatic hands were enrolled as cases and controls, respectively. The diagnostic efficiency of the extended EMLA test was found to be 83.4% for digit 2 and 87.3% for the lateral 4 digits (mean), whereas the diagnostic efficiency of standard NCS was 88.1%. Boston SSS and NPSI were better correlated with EMLA positivity than NCS positivity. A linear regression analysis showed negative correlation of wrinkling grade with NCS grade.

Conclusion:

With its improved diagnostic efficiency, the 90-min extended EMLA test can feasibly be used as an alternative to NCS, especially in general practice settings. Its potential clinical utility should be explored in a large population of CTS patients showing varying clinical and electrophysiological severities.

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.

The association of sensory phenotype and concomitant mood, sleep and functional impairment with the outcome of carpal tunnel surgery

BACKGROUND

Up to 25% of people who have had carpal tunnel release surgery (CTR) fail to report improvement; however, evidence for prognostic indicators in this surgical cohort is limited. To identify candidate prognostic factors, this study investigated the association of quantitative sensory testing (QST) derived sensory phenotype and attendant impairment with patient-reported surgical outcome.

METHODS

With ethical approval and informed consent, this prospective observational longitudinal study recruited patients from two London hospitals. Multimodal phenotyping measures including quantitative sensory testing (QST), pain parameters, insomnia, pain-related worry, mood and function, were evaluated prior to; and at 3- and 6-months post-surgery. Pain in median nerve distribution with electrophysiologically confirmed conduction delay and DN4 score ≥ 4 was defined as neuropathic. Primary outcome was patient-rated change at 6 months, dichotomised as poor outcome; "worse" or "no change" and good outcome; "slightly better", "much better" or "completely cured".

RESULTS

Seventy-six patients participated. Prior to surgery, substantial heterogeneity in established categories of somatosensory function was observed with 21% of participants categorised as having a healthy sensory phenotype; 29% with thermal hyperalgesia; 32% mechanical hyperalgesia and 18% sensory loss. Seventy six percent of participants were classified as having neuropathic pain, 33% with high levels of pain related worry and 64% with clinical insomnia. Observed differences in pain, sleep impairment, psychological factors and function, between sensory phenotypic groups, was not significant. At 3- and 6-months post-surgery there was significant improvement in all phenotyping measures with a moderate to large effect size. Thermal and mechanical measures of somatosensation improved (p < 0.001), as did functional ability (p < 0.001). Symptom severity diminished (p < 0.001), as did pain-related worry (p < 0.001), anxiety (p = 0.02) and insomnia (p < 0.001). Patient-rated surgical outcome was good in 92% of the cohort, poor in 8%. Baseline sensory phenotype category was not associated with surgical outcome however pain-related worry, anxiety and functional interference were significantly associated with outcome (p ≤ 0.05).

CONCLUSION

In patients undergoing carpal tunnel surgery, pain-related worry, anxiety and pain functional interference are candidate prognostic outcome factors and require further elucidation.

Application of digital infrared thermography for carpal tunnel syndrome evaluation

We investigated the thermographic findings of carpal tunnel syndrome (CTS). We enrolled 304 hands with electrodiagnostically identified CTS and 88 control hands. CTS hands were assigned to duration groups (D1, < 3 months; D2, 3‒6 months; D3, 6‒12 months; D4, ≥ 12 months) and severity groups (S1, very mild; S2, mild; S3, moderate; S4, severe). The temperature difference between the median and ulnar nerve territories (ΔM-U territories) decreased as CTS duration and severity increased. Significant differences in ΔM-U territories between the D1 and D3, D1 and D4, D2 and D4, and S1 and S4 groups (P = 0.003, 0.001, 0.001, and < 0.001, respectively) were observed. Thermal anisometry increased as CTS duration and severity increased. Significant differences in thermal anisometry between the D1 and D4 as well as the D2 and D4 groups (P = 0.005 and 0.04, respectively) were noted. Thermal anisometry was higher in the S4 group than in the S1, S2, and S3 groups (P = 0.009, < 0.001, and 0.003, respectively). As CTS progresses, skin temperature tends to decrease and thermal variation tends to increase in the median nerve-innervated area. Thermographic findings reflect the physiological changes of the entrapped median nerve.

The structure of sensory afferent compartments in health and disease

Primary sensory neurons are a heterogeneous population of cells able to respond to both innocuous and noxious stimuli. Like most neurons they are highly compartmentalised, allowing them to detect, convey and transfer sensory information. These compartments include specialised sensory endings in the skin, the nodes of Ranvier in myelinated axons, the cell soma and their central terminals in the spinal cord. In this review, we will highlight the importance of these compartments to primary afferent function, describe how these structures are compromised following nerve damage and how this relates to neuropathic pain.

[Entrapment neuropathies: a contemporary approach to pathophysiology, clinical assessment, and management : German version]

Entrapment neuropathies such as carpal tunnel syndrome, radiculopathies, or radicular pain are the most common peripheral neuropathies and also the most common cause for neuropathic pain. Despite their high prevalence, they often remain challenging to diagnose and manage in a clinical setting. Summarising the evidence from both preclinical and clinical studies, this review provides an update on the aetiology and pathophysiology of entrapment neuropathies. Potenzial mechanisms are put in perspective with clinical findings. The contemporary assessment is discussed and diagnostic pitfalls highlighted. The evidence for the noninvasive and surgical management of common entrapment neuropathies is summarised and future areas of research are identified.

Vibrotactile sense 5 years after carpal tunnel release in people with diabetes: A prospective study with matched controls

AIM

To compare vibrotactile sense, 5 years after carpal tunnel release in people with and without diabetes.

METHODS

Out of 35 people with diabetes and carpal tunnel syndrome, age- and gender-matched with 31 people without diabetes but with idiopathic carpal tunnel syndrome, 27 and 30 people, respectively, participated in this prolonged follow-up. Vibration perception threshold of the index and little finger (median and ulnar nerve, respectively), 5 years after surgery, was measured at seven different frequencies (8, 16, 32, 64, 125, 250 and 500 Hz).

RESULTS

Significant improvement of vibration perception threshold from 1 to 5 years after carpal tunnel release was found at 64 Hz for people with diabetes, while improvement for people without diabetes was demonstrated at several frequencies (64-250 Hz). However, both groups demonstrated a significant decrease in vibration perception threshold for the low frequencies (8-16 Hz). At 5 years, people with diabetes had significantly impaired vibration perception threshold at the index finger for high frequencies (125-500 Hz), and for nearly all frequencies (16 Hz, 64-500 Hz) at the little finger, compared to people without diabetes.

CONCLUSION

After carpal tunnel release, significant mid-term improvement of vibrotactile sense appears limited for people with diabetes, compared to a continuous improvement for people without diabetes. In addition, a decline in low-frequency vibrotactile sense occurs for the median as well as the ulnar nerve innervated fingers. Clinical Trial Registration NCT01201109.

Studying human nociceptors: from fundamentals to clinic

Chronic pain affects one in five of the general population and is the third most important cause of disability-adjusted life-years globally. Unfortunately, treatment remains inadequate due to poor efficacy and tolerability. There has been a failure in translating promising preclinical drug targets into clinic use. This reflects challenges across the whole drug development pathway, from preclinical models to trial design. Nociceptors remain an attractive therapeutic target: their sensitization makes an important contribution to many chronic pain states, they are located outside the blood-brain barrier, and they are relatively specific. The past decade has seen significant advances in the techniques available to study human nociceptors, including: the use of corneal confocal microscopy and biopsy samples to observe nociceptor morphology, the culture of human nociceptors (either from surgical or post-mortem tissue or using human induced pluripotent stem cell derived nociceptors), the application of high throughput technologies such as transcriptomics, the in vitro and in vivo electrophysiological characterization through microneurography, and the correlation with pain percepts provided by quantitative sensory testing. Genome editing in human induced pluripotent stem cell-derived nociceptors enables the interrogation of the causal role of genes in the regulation of nociceptor function. Both human and rodent nociceptors are more heterogeneous at a molecular level than previously appreciated, and while we find that there are broad similarities between human and rodent nociceptors there are also important differences involving ion channel function, expression, and cellular excitability. These technological advances have emphasized the maladaptive plastic changes occurring in human nociceptors following injury that contribute to chronic pain. Studying human nociceptors has revealed new therapeutic targets for the suppression of chronic pain and enhanced repair. Cellular models of human nociceptors have enabled the screening of small molecule and gene therapy approaches on nociceptor function, and in some cases have enabled correlation with clinical outcomes. Undoubtedly, challenges remain. Many of these techniques are difficult to implement at scale, current induced pluripotent stem cell differentiation protocols do not generate the full diversity of nociceptor populations, and we still have a relatively poor understanding of inter-individual variation in nociceptors due to factors such as age, sex, or ethnicity. We hope our ability to directly investigate human nociceptors will not only aid our understanding of the fundamental neurobiology underlying acute and chronic pain but also help bridge the translational gap.

Atraumatic proximal radial nerve entrapment. Illustrative cases and systematic review of literature

PURPOSE

The aims of the present study were to describe atraumatic proximal radial nerve entrapment (PRNE) and potential strategies for management.

MATERIALS AND METHODS

We performed a comprehensive search of 4 electronic databases for studies pertaining to patients with atraumatic PRNE. Studies published between 1930 and 2020 were included. Clinical presentation, nerve conduction studies, electromyography, and treatment methods were reviewed. In order to outline management strategies, 2 illustrative cases of acute PRNE were presented.

RESULTS

We analyzed 12 studies involving 21 patients with 22 PRNE (15 acute and 7 progressive). Sudden or repetitive elbow extension with forceful muscle contraction (n = 16) was the primary mechanism of injury. The two main sites of entrapment were the fibrous arch (n = 7) and hiatus of the lateral intermuscular septum (n = 7). Conservative treatment was performed in 4 patients and allowed for complete clinical recovery in all cases. The remaining 18 patients underwent epineurolysis (n = 16) or resection/repair of hourglass-like constriction (n = 2) between 1.5- and 120-months following diagnosis. Twelve patients experience complete recovery, while partial or no clinical recovery was reported in 1 and 4 cases, respectively; the outcome was unknown in 1 case.

CONCLUSIONS

Atraumatic PRNE is rare and remains challenging with respect to diagnosis and treatment. Current literature suggests that primary sites of entrapment are the fibrous arch and hiatus of the radial nerve at the time of forceful elbow extension.

LEVEL OF EVIDENCE

Case series (IV) & systematic review (I).

Manual Therapy as a Management of Cervical Radiculopathy: A Systematic Review

BACKGROUND

Cervical radiculopathy is defined as a disorder involving dysfunction of the cervical nerve roots characterised by pain radiating and/or loss of motor and sensory function towards the root affected. There is no consensus on a good definition of the term. In addition, the evidence regarding the effectiveness of manual therapy in radiculopathy is contradictory.

OBJECTIVE

To assess the effectiveness of manual therapy in improving pain, functional capacity, and range of motion in treating cervical radiculopathy with and without confirmation of altered nerve conduction.

METHODS

Systematic review of randomised clinical trials on cervical radiculopathy and manual therapy, in PubMed, Web of Science, Scopus, PEDro, and Cochrane Library Plus databases. The PRISMA checklist was followed. Methodological quality was evaluated using the PEDro scale and RoB 2.0. tool.

RESULTS

17 clinical trials published in the past 10 years were selected. Manual therapy was effective in the treatment of symptoms related to cervical radiculopathy in all studies, regardless of the type of technique and dose applied.

CONCLUSIONS

This systematic review did not establish which manual therapy techniques are the most effective for cervical radiculopathy with electrophysiological confirmation of altered nerve conduction. Without this confirmation, the application of manual therapy, regardless of the protocol applied and the manual therapy technique selected, appears to be effective in reducing chronic cervical pain and decreasing the index of cervical disability in cervical radiculopathy in the short term. However, it would be necessary to agree on a definition and diagnostic criteria of radiculopathy, as well as the definition and standardisation of manual techniques, to analyse the effectiveness of manual therapy in cervical radiculopathy in depth.

The Use of Quantitative Sensation Testing to Identify the Physiological Differences Between the Median and Ulnar Nerves

Introduction

Similarities in morphology, physiological function, and neurophysiological findings between median and ulnar nerves are not unequivocal. Our previous study confirmed differences in motor fiber parameters between these nerves in healthy persons. We made an attempt to assess and compare the physiological parameters of different sensation modalities (temperature, pain, and vibration) in median and ulnar nerves.

Methods

The study was performed in 31 healthy, right-handed volunteers: 17 women, 14 men, mean age 44.8 ± 15.5 years. Standard sensory conduction tests in the median and ulnar nerves were performed together with the estimation of vibratory, temperature, and warm- and cold-induced pain thresholds in the C7 and C8 dermatomes on the palm, using quantitative sensory testing.

Results

There were no statistically significant differences in the standard sensory conduction test in the median and ulnar nerves across the whole group: between right and left hands, and between women and men. We revealed differences in the temperature and pain thresholds between these nerves, mainly in low temperature perception. There were no differences in estimated thresholds between sides or in female and male groups. The vibratory limits did not differ significantly between nerves, and subgroups.

Conclusion

The study confirmed the differences in the physiological sensory perception between the median and ulnar nerves. The median nerve is more sensitive to temperature stimulation than the ulnar nerve, but simultaneously less sensitive to pain-inducing temperature stimuli. These findings should be considered during the examination of hand nerve pathology.

Cutaneous Neuroimmune Interactions in Peripheral Neuropathic Pain States

Bidirectional interplay between the peripheral immune and nervous systems plays a crucial role in maintaining homeostasis and responding to noxious stimuli. This crosstalk is facilitated by a variety of cytokines, inflammatory mediators and neuropeptides. Dysregulation of this delicate physiological balance is implicated in the pathological mechanisms of various skin disorders and peripheral neuropathies. The skin is a highly complex biological structure within which peripheral sensory nerve terminals and immune cells colocalise. Herein, we provide an overview of the sensory innervation of the skin and immune cells resident to the skin. We discuss modulation of cutaneous immune response by sensory neurons and their mediators (e.g., nociceptor-derived neuropeptides), and sensory neuron regulation by cutaneous immune cells (e.g., nociceptor sensitization by immune-derived mediators). In particular, we discuss recent findings concerning neuroimmune communication in skin infections, psoriasis, allergic contact dermatitis and atopic dermatitis. We then summarize evidence of neuroimmune mechanisms in the skin in the context of peripheral neuropathic pain states, including chemotherapy-induced peripheral neuropathy, diabetic polyneuropathy, post-herpetic neuralgia, HIV-induced neuropathy, as well as entrapment and traumatic neuropathies. Finally, we highlight the future promise of emerging therapies associated with skin neuroimmune crosstalk in neuropathic pain.

Pinprick Evoked Potentials-Reliable Acquisition in Healthy Human Volunteers

OBJECTIVE

Pinprick evoked potentials (PEPs) represent a novel tool to assess the functional integrity of mechano-nociceptive pathways with a potential toward objectifying sensory deficits and gain seen in neurological disorders. The aim of the present study was to evaluate the feasibility and reliability of PEPs with respect to age, stimulation site, and skin type.

METHODS

Electroencephalographic responses evoked by two pinprick stimulation intensities (128 mN and 256 mN) applied at three sites (hand dorsum, palmar digit II, and foot dorsum) were recorded in 30 healthy individuals. Test-retest reliability was performed for the vertex negative-positive complex amplitudes, N-latencies, and pain ratings evoked by the 256mN stimulation intensity.

RESULTS

Feasibility of PEP acquisition was demonstrated across age groups, with higher proportions of evoked potentials (>85%) for the 256mN stimulation intensity. Reliability analyses, that is, Bland-Altman and intraclass correlation coefficients, revealed poor to excellent reliability upon retest depending on the stimulation sites.

CONCLUSIONS

This study highlights the reliability of PEP acquisition from cervical and lumbar segments across clinically representative age groups. Future methodological improvements might further strengthen PEP reliability in order to complement clinical neurophysiology of sensory nerve fibers by a more specific assessment of mechano-nociceptive pathways. Beyond looking at sensory deficits, PEPs may also become applicable to revealing signs of central sensitization, complementing the clinical assessment of mechanical hyperalgesia.

Pinprick and Light Touch Are Adequate to Establish Sensory Dysfunction in Patients with Lumbar Radicular Pain and Disc Herniation

BACKGROUND

The frequency with which sensory disturbances occur in patients with radicular leg pain and disc herniation is not well known, and the efficacy of tests to identify such changes are not firmly established. The presence of sensory disturbances is a key sign of nerve root involvement and may contribute to the diagnosis of a lumbar disc herniation, identify patients for referral to spinal imaging and surgery, and improve disease classification.

QUESTIONS/PURPOSES

In this study, we sought: (1) to determine the frequency with which abnormal sensory findings occur in patients with lumbar disc herniation-related radicular pain, using a standard neurological sensory examination; (2) to determine what particular standard sensory test or combination of tests is most effective in establishing sensory dysfunction; and (3) to determine whether a more detailed in-depth sensory examination results in more patients being identified as having abnormal sensory findings.

METHODS

Between October 2013 and April 2016, 115 patients aged 18 to 65 years referred to secondary health care with radicular leg pain and disc herniation were considered potentially eligible for inclusion in the study. Based on these inclusion criteria, 79% (91) were found eligible. Ten percent (11) were excluded because of other illness that interfered with the study purpose, 3% (3) because of cauda equina syndrome, 2% (2) because of spinal stenosis, 2% (2) because of prior surgery at the same disc level, and 2% (2) because of poor Norwegian language skills. Three percent (4) of the patients did not want to participate in the study. Of the 91 eligible patients, 56% (51) consented to undergo a comprehensive clinical examination and were used for analysis here. The sample for the purposes of the present study was predetermined at 50. These patients were first examined by a standard procedure, including sensory assessment of light touch, pinprick, vibration, and warmth and cold over the back and legs. Second, an in-depth semiquantitative sensory testing procedure was performed in the main pain area to assess sensory dysfunction and improve the detection of potential positive sensory signs, or sensory gain of function more precisely. Sensory loss was defined as sensations experienced as distinctly reduced in the painful side compared with the contralateral reference side. In contrast, sensory gain was defined as sensations experienced as abnormally strong, unpleasant, or painful and distinctly stronger than the contralateral side. Ambiguous test results were coded as a normal response to avoid inflating the findings. The proportions of abnormal findings were calculated for each sensory modality and for all combinations of the standard examination tests.

RESULTS

The standard examination identified at least one abnormal finding in 88% (45 of 51) of patients. Sensory loss was present in 80% (41), while sensory gain was present in 35% (18). The combination of pinprick and light touch identified all patients who were classified as having abnormal findings by the full standard examination. The semiquantitative procedure identified an additional three patients with an abnormal finding.

CONCLUSION

We suggest that the combination of pinprick and light touch assessment is an adequate minimal approach for diagnostic and classification purposes in patients with lumbar radicular pain.

LEVEL OF EVIDENCE

Level I, diagnostic study.

Somatosensory and psychological phenotypes associated with neuropathic pain in entrapment neuropathy

ABSTRACT

It currently remains unclear why some patients with entrapment neuropathies develop neuropathic pain (neuP), whereas others have non-neuP, presumably of nociceptive character. Studying patients with carpal tunnel syndrome (CTS), this cross-sectional cohort study investigated changes in somatosensory structure and function as well as emotional well-being specific to the presence and severity of neuP. Patients with CTS (n = 108) were subgrouped by the DN4 questionnaire into those without and with neuP. The latter group was further subdivided into mild and moderate/severe neuP using a pain visual analogue scale. N = 32 participants served as healthy controls. All participants underwent a clinical examination, quantitative sensory testing, electrodiagnostic testing (EDT), and skin biopsy to determine the structural integrity of dermal and intraepidermal nerve fibres. Patients also completed questionnaires evaluating symptom severity and functional deficits, pain distribution, sleep quality, and emotional well-being. The overall prevalence of neuP in patients with CTS was 80%, of which 63% had mild neuP. Symptom severity and functional deficits as well as somatosensory dysfunction was more pronounced with the presence and increasing severity of neuP. No difference was identified among patient groups for EDT and nerve fibre integrity on biopsies. The severity of neuP was accompanied by more pronounced deficits in emotional well-being and sleep quality. Intriguingly, extraterritorial spread of symptoms was more prevalent in patients with moderate/severe neuP, indicating the presence of central mechanisms. NeuP is common in patients with CTS, and its severity is related to the extent of somatosensory dysfunction and a compromise of emotional well-being.

Effectiveness of Conservative Treatment According to Severity and Systemic Disease in Carpal Tunnel Syndrome: A Systematic Review

(1) Background: Carpal tunnel syndrome (CTS) is the most common peripheral neuropathy in the upper extremity. Conservative treatment has been effective for mild and moderate idiopathic CTS. However, severe CTS and systemic conditions were an exclusion criterion from the studies. The aim of this study is to review the effectiveness of conservative treatment in patients with CTS regardless of the level of severity and the presence or not of systemic diseases in the last ten years. (2) Methods: Randomized controlled clinical trials that compared the effect of conservative treatment on the Boston questionnaire and pain were selected. PubMed, PEDro, Scopus, Cochrane, and Web of Science databases were used. PRISMA statement checklist was performed. (3) Results: 876 studies were recorded, 29 were selected. Pharmacology, Electrotherapy and Manual Therapy had benefits for CTS. Electrotherapy and manual therapy could be effective for severe CTS patients with a systemic condition in the short term, but there was a low percentage of these patients included in the studies. (4) Conclusion: Some pharmacological treatments, manual therapy and electrotherapy have shown benefits for handling CTS, although the most effective combination of techniques is unknown. It would be necessary to include patients with systemic conditions in the selection criteria for future studies.

Molecular and cellular correlates of human nerve regeneration: ADCYAP1/PACAP enhance nerve outgrowth

We only have a rudimentary understanding of the molecular and cellular determinants of nerve regeneration and neuropathic pain in humans. This cohort study uses the most common entrapment neuropathy (carpal tunnel syndrome) as a human model system to prospectively evaluate the cellular and molecular correlates of neural regeneration and its relationship with clinical recovery. In 60 patients undergoing carpal tunnel surgery [36 female, mean age 62.5 (standard deviation 12.2) years], we used quantitative sensory testing and nerve conduction studies to evaluate the function of large and small fibres before and 6 months after surgery. Clinical recovery was assessed with the global rating of change scale and Boston Carpal Tunnel Questionnaire. Twenty healthy participants provided normative data [14 female, mean age 58.0 (standard deviation 12.9) years]. At 6 months post-surgery, we noted significant recovery of median nerve neurophysiological parameters (P < 0.0001) and improvements in quantitative sensory testing measures of both small and large nerve fibre function (P < 0.002). Serial biopsies revealed a partial recovery of intraepidermal nerve fibre density [fibres/mm epidermis pre: 4.20 (2.83), post: 5.35 (3.34), P = 0.001], whose extent correlated with symptom improvement (r = 0.389, P = 0.001). In myelinated afferents, nodal length increased postoperatively [pre: 2.03 (0.82), post: 3.03 (1.23), P < 0.0001] suggesting that this is an adaptive phenomenon. Transcriptional profiling of the skin revealed 31 differentially expressed genes following decompression, with ADCYAP1 (encoding pituitary adenylate cyclase activating peptide, PACAP) being the most strongly upregulated (log2 fold-change 1.87, P = 0.0001) and its expression was associated with recovery of intraepidermal nerve fibres. We found that human induced pluripotent stem cell-derived sensory neurons expressed the receptor for PACAP and that this peptide could significantly enhance axon outgrowth in a dose-dependent manner in vitro [neurite length PACAP 1065.0 µm (285.5), vehicle 570.9 μm (181.8), P = 0.003]. In conclusion, carpal tunnel release is associated with significant cutaneous reinnervation, which correlates with the degree of functional improvement and is associated with a transcriptional programme relating to morphogenesis and inflammatory processes. The most highly dysregulated gene ADCYAP1 (encoding PACAP) was associated with reinnervation and, given that this peptide signals through G-protein coupled receptors, this signalling pathway provides an interesting therapeutic target for human sensory nerve regeneration.

3-photon microscopy of myelin in mouse digital skin excited at the 1700-nm window

Myelin is a key component of the peripheral nervous system, whose structure anomaly in the digital skin is implicated in neuropathy. Here we demonstrate an in vivo labeling and imaging technique, capable of visualizing myelin sheaths deep in the mouse digital skin. Through material characterization, we verify that 3-photon fluorescence (3PF) can be generated from a commonly used dye- FluoroMyelin Red for labeling myelin, excited at the 1700-nm window. Topical injection of FluoroMyelin Red in the mouse digit leads to bright labeling of myelin sheaths. Harnessing the deep-penetration capability of 3-photon microscopy excited at the 1700-nm window, we demonstrate that 3PF imaging of FluoroMyelin Red-labeled myelin sheaths in the mouse digit in vivo can be achieved to a depth 340 μm below the skin surface, revealing both branching bundle of and individual myelin sheaths.

Deletion of the Gene Encoding the NMDA Receptor GluN1 Subunit in Schwann Cells Causes Ultrastructural Changes in Remak Bundles and Hypersensitivity in Pain Processing

Abnormalities in interactions between sensory neurons and Schwann cells (SCs) may result in heightened pain processing and chronic pain states. We previously reported that SCs express the NMDA receptor (NMDA-R), which activates cell signaling in response to glutamate and specific protein ligands, such as tissue-type plasminogen activator. Herein, we genetically targeted grin1 encoding the essential GluN1 NMDA-R subunit, conditionally in SCs, to create a novel mouse model in which SCs are NMDA-R-deficient (GluN1- mice). These mice demonstrated increased sensitivity to light touch, pinprick, and thermal hyperalgesia in the absence of injury, without associated changes in motor function. Ultrastructural analysis of adult sciatic nerve in GluN1- mice revealed increases in the density of Aδ fibers and Remak bundles and a decrease in the density of Aβ fibers, without altered g-ratios. Abnormalities in adult Remak bundle ultrastructure were also present including aberrant C-fiber ensheathment, distances between axons, and increased poly-axonal pockets. Developmental and post radial sorting defects contributed to altered nerve fiber densities in adult. Uninjured sciatic nerves in GluN1- mice did not demonstrate an increase in neuroinflammatory infiltrates. Transcriptome profiling of dorsal root ganglia (DRGs) revealed 138 differentially regulated genes in GluN1- mice. One third of the regulated genes are known to be involved in pain processing, including sprr1a, npy, fgf3, atf3, and cckbr, which were significantly increased. The intraepidermal nerve fiber density (IENFD) was significantly decreased in the skin of GluN1- mice. Collectively, these findings demonstrate that SC NMDA-R is essential for normal PNS development and for preventing development of pain states.SIGNIFICANCE STATEMENT Chronic unremitting pain is a prevalent medical condition; however, the molecular mechanisms that underlie heightened pain processing remain incompletely understood. Emerging data suggest that abnormalities in Schwann cells (SCs) may cause neuropathic pain. We established a novel mouse model for small fiber neuropathy (SFN) in which grin1, the gene that encodes the NMDA receptor (NMDA-R) GluN1 subunit, is deleted in SCs. These mice demonstrate hypersensitivity in pain processing in the absence of nerve injury. Changes in the density of intraepidermal small fibers, the ultrastructure of Remak bundles, and the transcriptome of dorsal root ganglia (DRGs) provide possible explanations for the increase in pain processing. Our results support the hypothesis that abnormalities in communication between sensory nerve fibers and SCs may result in pain states.

High prevalence of carpal tunnel syndrome in individuals with rare nerve growth factor-beta mutation

In Sweden, a large family with a point mutation in the nerve growth factor-beta gene has previously been identified. The carriers of this mutation have reduced small-fibre density and selective deficits in deep pain and temperature modalities. The clinical findings in this population are described as hereditary sensory and autonomic neuropathy type V. The purpose of the current study was to investigate the prevalence of carpal tunnel syndrome in hereditary sensory and autonomic neuropathy type V based on clinical examinations and electrophysiological measurements. Furthermore, the cross-sectional area of the median nerve at the carpal tunnel inlet was measured with ultrasonography. Out of 52 known individuals heterozygous for the nerve growth factor-beta mutation in Sweden, 23 participated in the current study (12 males, 11 females; mean age 55 years; range 25–86 years). All participants answered a health questionnaire and underwent clinical examination followed by median nerve conduction study in a case–control design, and measurement of the nerve cross-sectional area with ultrasonography. The diagnosis of carpal tunnel syndrome was made based on consensus criteria using patient history and nerve conduction study. The prevalence of carpal tunnel syndrome in the hereditary sensory and autonomic neuropathy group was 35% or 52% depending on whether those individuals who had classic symptoms of carpal tunnel syndrome but negative nerve conduction studies were included or not. Those who had a high likelihood of carpal tunnel syndrome based on classic/probable patient history with positive nerve conduction study had a significantly larger median nerve cross-sectional area than those who had an unlikely patient history with negative nerve conduction study. The prevalence of carpal tunnel syndrome was 10–25 times higher in individuals heterozygous for the nerve growth factor-beta mutation than the general Swedish population. Further studies are needed to better understand the underlying pathophysiological mechanisms.

Entrapment neuropathies: a contemporary approach to pathophysiology, clinical assessment, and management

Entrapment neuropathies such as carpal tunnel syndrome, radiculopathies, or radicular pain are the most common peripheral neuropathies and also the most common cause for neuropathic pain. Despite their high prevalence, they often remain challenging to diagnose and manage in a clinical setting. Summarising the evidence from both preclinical and clinical studies, this review provides an update on the aetiology and pathophysiology of entrapment neuropathies. Potential mechanisms are put in perspective with clinical findings. The contemporary assessment is discussed and diagnostic pitfalls highlighted. The evidence for the noninvasive and surgical management of common entrapment neuropathies is summarised and future areas of research are identified.

Rapid Stretch Injury to Peripheral Nerves: Biomechanical Results

BACKGROUND

Although most adult brachial plexus injuries result from high-speed mechanisms, no laboratory model has been created to mimic rapid-stretch nerve injuries. Understanding the biomechanical response of nerves to rapid stretch is essential to understanding clinical injury patterns and developing models that mimic the clinical scenario.

OBJECTIVE

To assess the influence of rate, loading direction, and excursion of stretch injuries on the biomechanical properties of peripheral nerves.

METHODS

The sciatic nerves of 138 Sprague-Dawley rats were dissected and subjected to rapid- and slow-stretch methods. Maximal nerve strain, persistent deformation, regional strain variation, and location of nerve failure were recorded.

RESULTS

Nerve rupture was primarily determined by weight-drop momentum >1 N/sec (odds ratio = 27.8, P < .0001), suggesting a threshold condition. Loading direction strongly determined maximal strain at rupture (P = .028); pull along the nerve axis resulted in nerve rupture at lower strain than orthogonal loading. Regional variations in nerve compliance and rupture location correlated with anatomic zones. Nerve branch anatomy was the largest contributing factor on maximum strain and rupture location. Rapidly stretched nerves are characterized by a zone of elastic recovery, followed by inelastic response at increasing strain, and finally rupture.

CONCLUSION

The large variation in previous results for nerve strain at rupture can be attributed to different testing conditions and is largely due to loading direction or segment of nerve tested, which has significant clinical implications. Nerve stretch injuries do not reflect a continuous variability to applied force but instead fall into biomechanical patterns of elastic, inelastic, and rupture injuries.

The optimum hand temperature to study nerve conduction in patients with carpal tunnel syndrome

To define the skin temperature at which diseased nerves are better differentiated from the healthy. Motor and sensory conduction of median and ulnar nerve were evaluated in 52 patients with carpal tunnel syndrome (CTS) and 52 matched healthy controls at environmental skin temperature (mean 32-33 °C), after warming by an average of 2 °C and cooling to approximately 6 °C below baseline. In the hot condition, group comparisons for the median nerve showed a similar rate of distal motor latency (DML) reduction and sensory conduction velocity (SCV) increase in CTS and controls. With cold, the rate of change was smaller for the patients: DML mean increase was 5% /°C (7% for controls) and SCV mean decrease was 2.5%/°C (3.2% for controls). Individual patients' analysis revealed fewer abnormal median DML and SCV values at hot or at cold, compared to environmental temperature. It is concluded that conduction adjustments for low hand temperatures based on healthy measurements resulted in overcorrection and therefore underdiagnosis of CTS. Alternatively, at excessive hand warming the convergence of patient and healthy measurements also lead to underdiagnosis. Maintenance of skin temperature at 32-33 °C, corresponding to normal body temperature, is the optimum approach and should always be employed in clinical practice.

Serum levels of inflammatory cytokines in patients with idiopathic carpal tunnel syndrome

Objectives: Carpal tunnel syndrome (CTS) is a disorder caused by median nerve pressure inside the carpal tunnel in the wrist area. Recent evidences have demonstrated a role of cytokines in CTS. It is still controversial whether idiopathic CTS is an inflammatory or non-inflammatory disorder. Accordingly, the purpose of the current research was to assess serum levels of inflammatory cytokines in patients with idiopathic carpal tunnel syndrome in comparison with healthy participants.Methods: This case-control research was performed on 40 female patients with idiopathic carpal tunnel syndrome and 40 healthy controls. After identifying the participants, the serum levels of four cytokines (TNF-α, IL-2, IL-4, IL-6, and IL-10) were calculated by ELIZA method. SPSS statistical analysis was performed after entering data. p-values ≤ 0.05 was deliberated statistically significant.Results: The mean age was 45.07 ± 8.52 years in the patient group and 45.32 ± 8.42 years in the control group. The concentration of TNFα, IL1, IL6 and IL10 was 3.84 ± 0.44, 3.20 ± 0.71, 3.37 ± 1.26 and 6.21 ± 3.38 in patient group. The current study results demonstrated that there was no statistically significant difference among the case and control groups.Conclusions: This study showed that, serum levels of inflammatory cytokines (IL1, IL6, IL10 and TNFα) had no meaningful changes in patients with carpal tunnel syndrome and the role of these inflammatory mediators in this disease is still unclear.

Phenytoin Cream for the Treatment of Sciatic Pain: Clinical Effects and Theoretical Considerations: Case Report

Chronic sciatic pain is difficult to treat. Patients often suffer from considerable pain and are severely hampered in their everyday activities. Most pharmacologic analgesic treatments have disappointing effects, and often are limited due to adverse events. New treatments are therefore needed. Surprisingly we found fast pain reduction after applying topical phenytoin cream at the painful dermatome in a 55-year-old patient suffering from sciatic pain due to pathology of a disc. This patient was treatment resistant for 13 years. Prescribing topical analgesic cream seemed to us at first sight quite counter-intuitive. The clear response in a treatment-resistant patient however provoked us to look deeper in the pathophysiology of sciatic nerve impingement. Recently it has been documented that proximal nerve lesions are followed by small fiber pathology in the skin. This might be a responsible peripheral wind-up generator for the chronification of pain in sciatic nerve compression. Topical application of the broad-acting voltage-gated sodium channel blocker phenytoin could reduce neuropathic pain in our case completely, supporting a peripheral mechanism of action for phenytoin cream in sciatic pain.