Current and future applications of ultrasound imaging in peripheral nerve disorders

Exploring Divergent Electrodiagnostic and Sonographic Findings in Patients With Suspected Carpal Tunnel Syndrome: Role of Median Nerve Cross-Sectional Area

OBJECTIVES

Evaluate electrophysiologic and sonographic findings in patients with suspected carpal tunnel syndrome (CTS) that had divergent electrodiagnostic (EDX) and ultrasound imaging (USI) diagnoses of CTS.

METHODS

Retrospective analysis of 665 limbs from patients who underwent EDX testing and USI. MANOVA, Chi Square, and correlations were used to analyze electrophysiologic and sonographic variables in limbs with divergent findings. CTS diagnosis was determined using EDX- and USI-based classification systems, stratified by median nerve cross-sectional area (CSA) cutoff values producing large conclusive or small questionable shifts in diagnostic probability.

RESULTS

The proportion of limbs with a USI diagnosis of CTS but normal electrophysiologic findings was 17% and 35% when considering CSA cutoff values producing large conclusive and small questionable shifts in diagnostic probability, respectively. These limbs had significantly slower median sensory and motor latencies and larger distal and delta CSA compared to limbs with concordant findings. Conversely, the proportion of limbs with an EDX diagnosis of CTS but normal sonographic findings was 6% and 35% when considering CSA cutoff values producing large conclusive and small questionable shifts in diagnostic probability, respectively. These limbs had faster median motor latency, larger proximal and smaller distal and delta CSA compared to limbs with concordant findings.

CONCLUSIONS

Median nerve CSA proved to be the most reliable and clinically meaningful factor in limbs with divergent EDX and USI diagnoses of CTS regardless of diagnostic accuracy threshold. These results underscore the importance of integrating EDX testing and USI in patients with suspected CTS, particularly in cases with inconclusive or conflicting findings.

Clinical practice guidelines for the diagnosis and management of Charcot-Marie-Tooth disease

INTRODUCTION

Charcot-Marie-Tooth disease (CMT) is classified according to neurophysiological and histological findings, the inheritance pattern, and the underlying genetic defect. The objective of these guidelines is to offer recommendations for the diagnosis, prognosis, follow-up, and treatment of this disease in Spain.

MATERIAL AND METHODS

These consensus guidelines were developed through collaboration by a multidisciplinary panel encompassing a broad group of experts on the subject, including neurologists, paediatric neurologists, geneticists, physiatrists, and orthopaedic surgeons.

RECOMMENDATIONS

The diagnosis of CMT is clinical, with patients usually presenting a common or classical phenotype. Clinical assessment should be followed by an appropriate neurophysiological study; specific recommendations are established for the parameters that should be included. Genetic diagnosis should be approached sequentially; once PMP22 duplication has been ruled out, if appropriate, a next-generation sequencing study should be considered, taking into account the limitations of the available techniques. To date, no pharmacological disease-modifying treatment is available, but symptomatic management, guided by a multidiciplinary team, is important, as is proper rehabilitation and orthopaedic management. The latter should be initiated early to identify and improve the patient's functional deficits, and should include individualised exercise guidelines, orthotic adaptation, and assessment of conservative surgeries such as tendon transfer. The follow-up of patients with CMT is exclusively clinical, and ancillary testing is not necessary in routine clinical practice.

Phosphotungstic Acid Staining to Visualize the Vagus Nerve Perineurium Using Micro-CT

BACKGROUND AND PURPOSE

Peripheral nerve stimulation is approved by the US Food and Drug Administration for treating various disorders, but it is often limited by side effects, highlighting the need for a clear understanding of fascicular and fiber organization to design selective therapies. Micro-CT imaging of contrast-stained nerves enables the visualization of tissue microstructures, such as the fascicular perineurium and vasculature. In this work, we evaluated phosphotungstic acid (PTA) as a contrast agent and assessed its compatibility with downstream histology.

METHODS

Human vagus nerve samples were collected from three embalmed cadavers and subjected to three different staining methods, followed by micro-CT imaging: Lugol's iodine, osmium tetroxide, and PTA. Contrast ratios of adjacent tissue microstructures (perineurium, interfascicular epineurium, and fascicle) were quantified for each stain and compared. We further developed a pipeline to optimize micro-CT scan acquisition parameters based on objective metrics for sharpness, noise, and pixel saturation. The PTA-stained samples underwent subsequent histological processing and staining with hematoxylin and eosin, Masson's trichrome, and immunohistochemistry and were assessed for tissue degradation.

RESULTS

PTA enhanced the visualization of perineurium, providing high contrast ratios compared to iodine and osmium tetroxide. Optimized scanning parameters for PTA-stained nerves (55 kV and 109 µA) effectively balanced noise and sharpness. While we found that PTA is generally nondestructive for downstream histology, higher concentrations and longer exposure could alter the optical density of nuclei and affect stain differentiation in special stains.

CONCLUSION

PTA serves as a valuable micro-CT contrast agent for nerve imaging, effective in visualizing the perineurium with minimal impact on histological integrity.

Neurovascular crossing patterns between leash of Henry and deep branch of radial nerve: implications for neurointervention and diagnostic imaging

OBJECTIVE

To detail the neurovascular crossing patterns between the leash of Henry (LoH) and the deep branch of the radial nerve (DBRN) in supination and pronation of the forearm, using imaging methods with anatomic correlation.

MATERIALS AND METHODS

This cross-sectional study was performed ex vivo with HRUS and MRI with anatomic correlation on 6 samples and in vivo with HRUS with Doppler on 55 participants scanned bilaterally. The in vivo participants were enrolled over a 6-month period. The crossing patterns between the LoH and DBRN were assessed ex vivo and in vivo. Additional morphological features of the DBRN, LoH, and fat plane were assessed in vivo only. Biometric features of the participants were recorded. Statistical analyses were performed using Shapiro-Wilk, parametric and non-parametric tests.

RESULTS

The most common neurovascular crossing pattern was the ascending branch of the radial recurrent artery (RRAab) crossing below (ex vivo: 83.3%, in vivo: 85.3%) and the muscular branch crossing above (ex vivo: 100%, in vivo: 63.2% %) the DBRN. Both the deep and superficial surfaces of the DBRN exhibited an intimate relationship with the vessels of the LoH. A positive correlation between vessel diameter and anthropometric factors was observed. In addition, the muscular branch exhibited a significantly smaller diameter than the RRAab.

CONCLUSION

Our study detailed the relationship between the LoH and the DBRN and highlighted the high incidence of vessel crossing above the DBRN at the level of the muscular branch. Knowledge of neurovascular crossings is crucial for understanding neurovascular entrapment syndromes and planning interventional procedures to reduce vascular complications.

High-Resolution US vs MR Neurography for Diagnosis of Upper Extremity Peripheral Nerve Disorders

"Just Accepted" papers have undergone full peer review and have been accepted for publication in Radiology. This article will undergo copyediting, layout, and proof review before it is published in its final version. Please note that during production of the final copyedited article, errors may be discovered which could affect the content. Background High-resolution imaging methods contribute important pathomorphological information in diagnosing peripheral nerve disorders, but their diagnostic roles remain unclear due to limited clinical evidence. Purpose To investigate the diagnostic performance of high-resolution nerve US (HRUS) and MR neurography (MRN). Materials and Methods This prospective observational, single-center cohort study included 800 patients referred for clinically suspected peripheral neuropathy of the upper extremity from November 2015 to February 2022. All patients underwent both HRUS and MRN, performed and interpreted independently by experienced neuroradiologists. Accuracy, sensitivity, and specificity of HRUS and MRN in diagnosing peripheral neuropathy correctly were calculated in reference to the final diagnosis, based on compound results of clinical, electrophysiological, imaging, and surgical/histopathological findings and compared by means of the McNemar's test and X2-Testing. Results In total 800 patients (431 male, 369 female; mean age 47.8 ± 16.5 years) were included. Overall, MRN provided higher accuracy (85.4% [95%CI: 82.7%, 87.8%] vs. 70.6% [95%CI: 67.3%, 73.8%], P<.001) and sensitivity (91.6% [95%CI: 89.1%,93.7%] vs. 68.7% [95%CI: 64.8%,72.3%], P<.001), while HRUS achieved higher specificity (76.0% [95%CI: 69.4%,81.9%] vs. 66.2% [95%CI: 59.1%,72.8%], P<.001) for diagnosing peripheral neuropathy correctly. Conclusion For diagnosing peripheral neuropathies of the upper extremity, MRN achieved higher accuracy and sensitivity while HRUS achieved higher specificity. See also the editorial by Deshmukh in this issue.

Education Research: Feasibility, Reliability and Educational Value of Neuromuscular Ultrasound Training in a Canadian Neurology Residency Program: A Pilot Study

Background and Objectives

Point-of-care neuromuscular ultrasound (NMUS) is increasingly used in the evaluation of peripheral nervous system disorders; however, there remains a gap in education and training for neurology residents. We evaluated whether neurology residents can feasibly be trained in basic NMUS skills and nerve cross-sectional area (CSA) measurement and whether they value incorporation of this training into their curriculum.

Methods

Participants included neurology residents (postgraduate years 1-5) at the University of Alberta (Edmonton, Alberta, Canada). All completed pretraining and posttraining surveys using a Likert scale, rating their confidence in independently performing NMUS and their degree of agreement regarding the educational value of NMUS training. Residents underwent training (7 hours) comprising 1 didactic and 2 hands-on sessions, detailing NMUS of median, ulnar, and fibular nerves. Participants could then opt-in to a posttraining testing session where CSA measurements (mm2) of the median, ulnar, and fibular nerve at multiple sites were independently performed on 3 healthy volunteers and compared with measurements obtained by the trainer.

Results

Eighteen residents participated in training and pretraining/posttraining surveys. Nine completed the testing component. Nerve CSA measurement reliability between the trainer and trainees across all nerve sites combined was very good (intraclass correlation coefficient [ICC] 0.93, 95% CI 0.83-0.96) but varied by nerve and site. ICC was good to very good (0.62-0.95) except for the ulnar nerve-distal forearm/wrist (0.39-0.58) and fibular nerve-fibular head (0.12) sites. The coefficient of variation (CoV) across all sites was 19.6% (95% CI 17.3-21.8) and best for the median nerve-wrist site at 15.5% (9.8-20.8). The mean absolute difference between trainer and trainee measurements was low (<0.5 mm2 across all sites). Comparing pretraining and posttraining survey responses, there was a significant increase in agreement that basic NMUS operational skills were obtained and in confidence in independently measuring each nerve. NMUS training was considered a valuable component of a neurology residency program curriculum (median rating: strongly agree).

Discussion

Neurology residents across stages of training can acquire basic NMUS and CSA measurement skills of the median and ulnar nerves after 2 half-days of training and value incorporation of NMUS training in their educational curriculum.

Advances in Imaging of Traumatic Nerve Injuries

Traumatic peripheral nerve injuries represent a spectrum of conditions and remain challenging to diagnose and prognosticate. High-resolution ultrasonography and magnetic resonance neurography have emerged as useful diagnostic modalities in the evaluation of traumatic peripheral nerve and brachial plexus injuries. Ultrasonography is noninvasive, is able to rapidly interrogate large areas and multiple nerves, allows for a dynamic assessment of nerves and their surrounding anatomy, and is cost-effective. It allows for the prompt differentiation of neurotmetic versus axonotmetic traumatic nerve injuries, which informs surgical decision making. Magnetic resonance neurography yields images of peripheral nerves with high structural resolution down to the level of fascicles, is able to evaluate difficult anatomic areas that may not be reached by ultrasonography, and can detect signs of acute and chronic muscle denervation. Advanced preclinical techniques, such as second-harmonic generation microscopy, use multiphoton microscopy to visualize the internal collagenous structure of peripheral nerves, while third-harmonic generation microscopy can image myelin. One potential future application for multiphoton microscopy is the in vivo real-time assessment of nervous tissue. Near-infrared fluorescence also has the potential to assist with intraoperative peripheral nerve identification and assessment of pathology, but many challenges remain in identifying or designing the ideal contrast agent.

Neck triangle nerve enlargement in hereditary transthyretin amyloidosis correlates with changes in the autonomic, cardiac, and gastrointestinal systems

BACKGROUND

Hereditary transthyretin amyloidosis (ATTRv) is a hereditary disease that affects multiple bodily systems. Although sonography generally reveals enlargement of nerves in the limbs, the brachial plexus, and vagus nerve, the clinical significance of these findings remains unclear.

METHODS

We performed sonographic measurements of the median nerve, cervical spinal nerves at the C5-C7 level, and the vagus nerve in patients with ATTRv and healthy controls. Clinical profiles and cardiac and gastrointestinal examination results were also collected for linear regression analysis.

RESULTS

We recruited 47 patients with ATTRv (males/females: 34/13, age: 65.6 ± 5.3 years). The sampled segments were all significantly larger than those of the controls. In the clinical profiles, the sum of the Z scores of the neck triangle nerves (cervical spinal nerves and vagus nerve) and of all nerves (cervical spinal nerves, vagus nerve, and median nerve at the wrist) significantly correlated with the familial amyloid polyneuropathy stage, onset of autonomic nervous system (ANS) symptoms, and autonomic symptom scores. On cardiac examinations, several ultrasonography and magnetic resonance imaging parameters (primarily those that reflect heart volume) were found to be significantly correlated with the sum of the Z scores of the cervical spinal nerves but not with the Z score of the vagus nerve. In gastrointestinal evaluation, the cross-sectional area of the vagus nerve was correlated with gastric emptying time parameters on scintigraphy.

CONCLUSIONS

Neck triangle nerve enlargement on sonography correlated with parameters related to ANS dysfunction, indicating that nerve enlargement observed on ultrasonography may serve as a potential surrogate biomarker of ATTRv.

Perceived discrepancies in neurosonology training and certification across Europe: a RRFS/EAN survey

Introduction

Neurosonology is a vital paraclinical investigation in modern neurology. However, access to education and certification in neurosonology for neurology residents and young specialists in Europe is challenging, and comprehensive data regarding this topic are scarce. Information regarding difficulties in neurosonology training across Europe may help bring this topic under the spotlight and act as a call for the harmonization of curricula across the continent.

Methods

We performed an online survey targeting European neurology residents and young specialists, focusing on neurosonology training and certification. The survey was conducted between May and September 2023 and received responses from 282 participants representing 37 European countries.

Results

There were disparities in neurosonology training during residency, with 6 (16.2%) out of 37 countries reporting a dedicated curriculum. The respondents expressed an overall lack of satisfaction with theoretical knowledge (rating their experience as very poor 28.0%, poor 20.2%, neutral 25.9%, good 19.3%, and very good 6.6%) and practical skills gained during their training (rating their experience as very poor 30.9%, poor 18.9%, neutral 22.6%, good 18.1%, and very good 9.5%). A total of 282 respondents (5.7%), 16 held a national certification in neurosonology, claiming obstacles such as high costs of certification and a limited number of certifying centers.

Discussion

This survey reveals significant variations in neurosonology training across Europe, indicating difficulties in obtaining certification. Despite the increasing importance of neurosonology, many neurologists feel inadequately prepared and lack practical training during residency, emphasizing the need for better and more standardized access.

Conclusion

The survey underscores challenges and disparities in neurosonology training and certification in Europe. Standardization of curricula and increased awareness about available certifications are crucial to address these issues. The interest in European Certification suggests a potential solution for enhancing neurosonology training at the international level.

Sonographic Measurement of Median Nerve Cross-Sectional Area to Determine Severity of Carpal Tunnel Syndrome: A Cautionary Tale

OBJECTIVES

Evaluate the diagnostic accuracy of median nerve cross-sectional area (CSA) to determine the severity of carpal tunnel syndrome (CTS) vs the presence of CTS across existing electrodiagnostic-based (EDX) classification systems.

METHODS

Retrospective analysis of cross-sectional patient data. Receiver operating characteristic (ROC) analysis was used to determine CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS severity. Identification of CSA cutoff values associated with likelihood ratios capable of achieving conclusive (but at least moderate) shifts in diagnostic probability.

RESULTS

Binary categorizations of CTS (ie, "Normal" vs "Absent") were statistically superior to consolidated categorizations of CTS severity (ie, "Normal," "Mild," "Moderate," or "Severe"). Binary categorizations established consistent CSA cutoff values across all EDX-based classifications examined and achieved conclusive shifts in diagnostic probability based on the following values of distal CSA or delta CSA: <7 or <1 mm2 to rule out and >13 or >7 mm2 to rule in CTS, respectively. Additionally, the following values of distal CSA and delta CSA may be used in certain circumstances because they produce only small shifts in diagnostic probability: ≤10 or ≤3 mm2 to rule out and ≥11 or ≥4 mm2 to rule in CTS, respectively.

CONCLUSIONS

Using median nerve CSA to categorize the severity of CTS is not recommended based on lack of consistent and meaningful shifts in diagnostic probability. Rather, binary categorizations to rule out or rule in CTS based on the proposed CSA cutoff values consistently provided conclusive shifts in diagnostic probability across all EDX-based classifications examined.

Median Nerve Cross-Sectional Area and Carpal Tunnel Syndrome in Specific Populations: Sonographic Analysis of Patients With Type 2 Diabetes or Bifid Anatomy

OBJECTIVES

Evaluate diagnostic accuracy of median nerve cross-sectional area (CSA) to determine severity versus presence of carpal tunnel syndrome (CTS) across existing electrodiagnostic-based (EDX) classification systems in patients with type 2 diabetes or bifid anatomy.

METHODS

Retrospective analysis of cross-sectional patient data. Receiver operating characteristic analysis used to determine median nerve CSA cutoff values and associated diagnostic likelihood ratios for all consolidated and binary EDX-based classifications of CTS in patients with type 2 diabetes or bifid anatomy. Determine shifts in diagnostic probability based on established cutoff values and associated likelihood ratios. Distal CSA measured at or near carpal tunnel inlet, proximal CSA at level of pronator quadratus muscle, and delta CSA by subtracting proximal from distal.

RESULTS

Binary categorizations of CTS were statistically superior to consolidated categorizations of CTS severity in patients with type 2 diabetes or bifid anatomy. Binary categorizations established reasonably consistent median nerve CSA cutoff values across all EDX-based classifications examined resulting in the following for distal CSA or delta CSA: ≤10 or ≤4 mm2 to rule out and ≥11 or ≥5 mm2 to rule in CTS, respectively. These cutoff values resulted in small shifts in diagnostic probability in patients with type 2 diabetes and small to conclusive shifts in diagnostic probability in patients with bifid anatomy.

CONCLUSIONS

Binary categorizations to rule out or rule in CTS based on the proposed cutoff values provide the most meaningful information about shifts in diagnostic probability across all EDX-based classifications examined. The use of median nerve CSA to categorize severity of CTS is not recommended in patients with type 2 diabetes or bifid anatomy.

Evaluating Outcomes Following Nerve Repair: Beyond the Medical Research Council

Peripheral nerve injuries are common and remain a significant health challenge. Outcome measurements are used to evaluate injury, monitor recovery after nerve repair, and compare scientific advances. Clinical judgement is required to determine which available tools are most applicable, which requires a vast understanding of the available outcome measurements. In this article we discuss the highest yield tools available for clinical application.

Advances in Imaging of Compressive Neuropathies

Ultrasound and magnetic resonance neurography are useful modalities to aid in the assessment of compressive neuropathies, although they are still limited in their resolution of nerve microstructure and their capacity to monitor postoperative nerve recovery. Optical coherence tomography, a preclinical imaging modality, is promising in its ability to better identify structural and potential physiologic changes to peripheral nerves, but requires additional testing and research prior to widespread clinical implementation. Further advances in nerve imaging may elucidate the ability to visualize the zone of nerve injury intraoperatively, monitor the progression of nerve regeneration, and localize problems during nerve recovery.

Foot drop in critically ill patients: a narrative review of an elusive complication with intricate implications for recovery and rehabilitation

Foot drop is a condition characterized by the inability to lift the foot upwards towards the shin bone. This condition may affect a proportion of critically ill patients, impacting on their recovery after the acute phase of the illness. The occurrence of foot drop in critical care patients may result from various underlying causes, including neurological injuries, muscular dysfunction, nerve compression, or vascular compromise. Understanding the etiology and assessing the severity of foot drop in these patients is essential for implementing appropriate management strategies and ensuring better patient outcomes. In this comprehensive review, we explore the complexities of foot drop in critically ill patients. We search for the potential risk factors that contribute to its development during critical illness, the impact it has on patients' functional abilities, and the various diagnostic techniques adopted to evaluate its severity. Additionally, we discuss current treatment approaches, rehabilitation strategies, and preventive measures to mitigate the adverse effects of foot drop in the critical care setting. Furthermore, we explore the roles of critical care physical therapists, neurologists, and other healthcare professionals in the comprehensive care of patients with foot drop syndrome and in such highlighting the importance of a multidisciplinary approach.

Parsonage-Turner Syndrome and Hereditary Brachial Plexus Neuropathy

Parsonage-Turner syndrome and hereditary brachial plexus neuropathy (HBPN) present with indistinguishable attacks of rapid-onset severe shoulder and arm pain, disabling weakness, and early muscle atrophy. Their combined incidence ranges from 3 to 100 in 100,000 persons per year. Dominant mutations of SEPT9 are the only known mutations responsible for HBPN. Parsonage and Turner termed the disorder "brachial neuralgic amyotrophy," highlighting neuropathic pain and muscle atrophy. Modern electrodiagnostic and imaging testing assists the diagnosis in distinction from mimicking disorders. Shoulder and upper limb nerves outside the brachial plexus are commonly affected including the phrenic nerve where diaphragm ultrasound improves diagnosis. Magnetic resonance imaging can show multifocal T2 nerve and muscle hyperintensities with nerve hourglass swellings and constrictions identifiable also by ultrasound. An inflammatory immune component is suggested by nerve biopsies and associated infectious, immunization, trauma, surgery, and childbirth triggers. High-dose pulsed steroids assist initial pain control; however, weakness and subsequent pain are not clearly responsive to steroids and instead benefit from time, physical therapy, and non-narcotic pain medications. Recurrent attacks in HBPN are common and prophylactic steroids or intravenous immunoglobulin may reduce surgical- or childbirth-induced attacks. Rehabilitation focusing on restoring functional scapular mechanics, energy conservation, contracture prevention, and pain management are critical. Lifetime residual pain and weakness are rare with most making dramatic functional recovery. Tendon transfers can be used when recovery does not occur after 18 months. Early neurolysis and nerve grafts are controversial. This review provides an update including new diagnostic tools, new associations, and new interventions crossing multiple medical disciplines.

Carpal tunnel syndrome

Median neuropathy at the wrist, commonly referred to as carpal tunnel syndrome (CTS), is the most common entrapment neuropathy. It is caused by chronic compression of the median nerve at the wrist within the space-limited carpal tunnel. Risk factors that contribute to the etiology of compression include female gender, obesity, work-related factors, and underlying medical conditions, such as hypothyroidism, pregnancy, and amyloidosis. The diagnosis is made on clinical grounds, although these can be confounded by anatomical variations. Electrodiagnostic studies, which are specific and sensitive in diagnosing CTS, support the diagnosis; however, a subgroup may present with normal results. The advent of imaging techniques, including ultrasound and MRI, further assists the diagnostic process. The management of CTS is divided into the nonsurgical approaches that include hand therapy, splinting and corticosteroid injection, and surgical decompression of the carpal tunnel. Although several surgical techniques have been developed, no one method is more effective than the other. Each of these management approaches are effective at providing symptom relief and are utilized at different severities of the condition. There is, however, a lack of consensus on standardized diagnostic criteria, as well as when and to whom to refer patients for surgery.

Quantitative evaluation of rat sciatic nerve degeneration using high-frequency ultrasound

In this study, we evaluated the utility of using high-frequency ultrasound to non-invasively track the degenerative process in a rat model of peripheral nerve injury. Primary analyses explored spatial and temporal changes in quantitative backscatter coefficient (BSC) spectrum-based outcomes and B-mode textural outcomes, using gray level co-occurrence matrices (GLCMs), during the progressive transition from acute to chronic injury. As secondary analyses, correlations among GLCM and BSC spectrum-based parameters were evaluated, and immunohistochemistry were used to suggest a structural basis for ultrasound outcomes. Both mean BSC spectrum-based and mean GLCM-based measures exhibited significant spatial differences across presurgical and 1-month/2-month time points, distal stumps enclosed proximity to the injury site being particularly affected. The two sets of parameters sensitively detected peripheral nerve degeneration at 1-month and 2-month post-injury, with area under the receiver operating charactersitic curve > 0.8 for most parameters. The results also indicated that the many BSC spectrum-based and GLCM-based parameters significantly correlate with each other, and suggested a common structural basis for a diverse set of quantitative ultrasound parameters. The findings of this study suggest that BSC spectrum-based and GLCM-based analysis are promising non-invasive techniques for diagnosing peripheral nerve degeneration.

Imaging diagnosis in peripheral nerve injury

Peripheral nerve injuries (PNIs) can be caused by various factors, ranging from penetrating injury to compression, stretch and ischemia, and can result in a range of clinical manifestations. Therapeutic interventions can vary depending on the severity, site, and cause of the injury. Imaging plays a crucial role in the precise orientation and planning of surgical interventions, as well as in monitoring the progression of the injury and evaluating treatment outcomes. PNIs can be categorized based on severity into neurapraxia, axonotmesis, and neurotmesis. While PNIs are more common in upper limbs, the localization of the injured site can be challenging. Currently, a variety of imaging modalities including ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI) and positron emission tomography (PET) have been applied in detection and diagnosis of PNIs, and the imaging efficiency and accuracy many vary based on the nature of injuries and severity. This article provides an overview of the causes, severity, and clinical manifestations of PNIs and highlights the role of imaging in their management.

Deep branch of the radial nerve: effect of pronation/supination on longitudinal nerve alignment

OBJECTIVE

To evaluate the effect of maximal pronation and supination of the forearm on the alignment and anatomic relationship of the deep branch of the radial nerve (DBRN) at the superior arcade of the supinator muscle (SASM) by using high-resolution ultrasound (HRUS).

MATERIALS AND METHODS

In this cross-sectional study, HRUS in the long axis of the DBRN was performed in asymptomatic participants enrolled from March to August 2021. DBRN alignment was evaluated by measuring angles of the nerve in maximal pronation and maximal supination of the forearm independently by two musculoskeletal radiologists. Forearm range of motion and biometric measurements were recorded. Student t, Shapiro-Wilk, Pearson correlation, reliability analyses, and Kruskal-Wallis test were used.

RESULTS

The study population included 110 nerves from 55 asymptomatic participants (median age, 37.0 years; age range, 16-63 years; 29 [52.7%] women). There was a statistically significant difference between the DBRN angle in maximal supination and maximal pronation (Reader 1: 95% CI: 5.74, 8.21, p < 0.001, and Reader 2: 95% CI: 5.82, 8.37, p < 0.001). The mean difference between the angles in maximal supination and maximal pronation was approximately 7° for both readers. ICC was very good for intraobserver agreement (Reader1: r ≥ 0.92, p < 0.001; Reader 2: r ≥ 0.93, p < 0.001), as well as for interobserver agreement (phase 1: r ≥ 0.87, p < 0.001; phase 2: r ≥ 0.90, p < 0.001).

CONCLUSION

The extremes of the rotational movement of the forearm affect the longitudinal morphology and anatomic relationships of the DBRN, primarily demonstrating the convergence of the nerve towards the SASM in maximal pronation and divergence in maximal supination.

A scoping review of current and emerging techniques for evaluation of peripheral nerve health, degeneration and regeneration: part 2, non-invasive imaging

Peripheral neuroregenerative research and therapeutic options are expanding exponentially. With this expansion comes an increasing need to reliably evaluate and quantify nerve health. Valid and responsive measures of the nerve status are essential for both clinical and research purposes for diagnosis, longitudinal follow-up, and monitoring the impact of any intervention. Furthermore, novel biomarkers can elucidate regenerative mechanisms and open new avenues for research. Without such measures, clinical decision-making is impaired, and research becomes more costly, time-consuming, and sometimes infeasible. Part 1 of this two-part scoping review focused on neurophysiology. In part 2, we identify and critically examine many current and emerging non-invasive imaging techniques that have the potential to evaluate peripheral nerve health, particularly from the perspective of regenerative therapies and research.

Longitudinal Movements and Stiffness of Lower Extremity Nerves Measured by Ultrasonography and Ultrasound Elastography in Symptomatic and Asymptomatic Populations: A Systematic Review With Meta-analysis

This study was aimed at analyzing the effectiveness of ultrasonography (US) and ultrasound elastography (UE) in evaluating longitudinal sliding and stiffness of nerves. In line with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, we analyzed 1112 publications (range: 2010-2021) extracted from MEDLINE, Scopus and Web of Science focusing on specific outcomes, including shear wave velocity (m/s), shear modulus (kPa), strain ratio (SR) and excursion (mm). Thirty-three papers were included and evaluated for overall quality and risk of bias. From the analysis of data concerning 1435 participants, mean shear wave velocity (SWV) in the sciatic nerve was 6.70 ± 1.26 m/s in controls and 7.51 ± 1.73 m/s in participants presenting with leg pain; in the tibial nerve, mean SWV was 3.83 ± 0.33 m/s in controls and 3.42 ± 3.53 m/s in participants presenting with diabetic peripheral neuropathy (DPN). The mean shear modulus (SM) was 20.9 ± 9.33 kPa for sciatic nerve, whereas it was an average of 23.3 ± 7.20 kPa for the tibial nerve. Considering 146 subjects (78 experimental, 68 controls) no significant difference was observed in SWV when comparing participants with DPN with controls (standard mean difference [SMD]: 1.26, 95% confidence interval [CI]: 0.54, 1.97), whereas a significant difference was observed in the SM (SMD: 1.78, 95% CI: 1.32, 2.25); furthermore, we found significant differences between left and right extremity nerves (SMD:1.14. 95% CI: 0.45, 1.83) among 458 participants (270 with DPN and 188 controls). No descriptive statistics are available for excursion because of the variability in participants and limb positions, whereas SR is considered only a semiquantitative outcome and therefore not comparable among different studies. Despite the presence of some limitations in study designs and methodological biases, on the basis of our findings, we can conclude that US and UE are effective methods in assessing longitudinal sliding and stiffness of lower extremity nerves in both symptomatic and asymptomatic subjects.

[Nerve biopsy in the diagnosis of peripheral neuropathies]

The indications for nerve biopsy have diminished in recent years. This examination nevertheless remains essential in certain cases of peripheral neuropathies, making it possible to specify the diagnosis or the mechanism of injury for a therapeutic purpose. It is a simple but "invasive" procedure, which can only be performed once on the same nerve. The indications are thus discussed on a case-by-case basis and based on a range of clinical, electrophysiological, biological or even genetic arguments. This involves close collaboration between clinical physicians and pathologists. The main difficulty of this biopsy concerns the fragility of the sample and the techniques necessary for its interpretation, requiring it to be carried out in expert centers. Nerve biopsy is closely related to skin biopsy in the search for small fiber neuropathy. It is a particular technique, but very well codified. The purpose of this review is to recall the indications and contraindications of nerve biopsy, and to explain what the contributions are but also the limits of this examination as well as of skin biopsy.

Peripheral focused ultrasound stimulation and its applications: From therapeutics to human-computer interaction

Peripheral focused ultrasound stimulation (pFUS) has gained increasing attention in the past few decades, because it can be delivered to peripheral nerves, neural endings, or sub-organs. With different stimulation parameters, ultrasound stimulation could induce different modulation effects. Depending on the transmission medium, pFUS can be classified as body-coupled US stimulation, commonly used for therapeutics or neuromodulation, or as an air-coupled contactless US haptic system, which provides sensory inputs and allows distinct human-computer interaction paradigms. Despite growing interest in pFUS, the underlying working mechanisms remain only partially understood, and many applications are still in their infancy. This review focused on existing applications, working mechanisms, the latest progress, and future directions of pFUS. In terms of therapeutics, large-sample randomized clinical trials in humans are needed to translate these state of art techniques into treatments for specific diseases. The airborne US for human-computer interaction is still in its preliminary stage, but further efforts in task-oriented US applications might provide a promising interaction tool soon.

Future Considerations in the Diagnosis and Treatment of Compressive Neuropathies of the Upper Extremity

Compressive neuropathies of the upper extremity are among the most common conditions seen by hand surgeons. The diagnoses of carpal tunnel syndrome and cubital tunnel syndrome have traditionally been made by a combination of history, physical examination, and electrodiagnostic testing. However, findings can be nonspecific and electrodiagnostic testing is invasive for the patient. The diagnosis of compressive neuropathies continues to evolve as technology advances, and newer diagnostic modalities predominantly focus on preoperative diagnostic imaging with ultrasound and magnetic resonance imaging/neurography. With the advent of cheaper, faster, and less invasive imaging, the future may bring a paradigm shift away from electrophysiology as the gold standard for the preoperative diagnosis of compressive neuropathies. Intraoperative imaging of nerve health is an emerging concept that warrants further investigation, whereas postoperative imaging of nerve recovery with ultrasound and magnetic resonance imaging currently has a limited role because of nonspecific findings and potential for misinterpretation. Advances in surgical treatment of compressive neuropathies appear to center around the use of imaging for less invasive neurolysis techniques and other adjunctive treatments with nerve decompression. The management of failed peripheral nerve decompressions and recurrent compressive neuropathies remains challenging.

Assessment of Motor Function in Peripheral Nerve Injury and Recovery

Introduction

Peripheral nerve injuries can be difficult to diagnose, treat, and monitor given their highly variable presentation. When the status of nerves is not accurately assessed, treatment may be delayed or overlooked and can result in lasting functional deficits. As our understanding of nerve repair and generation evolves, so will tools for evaluating both the functional and morphological status of peripheral nerves.

Objective

There is currently no single article which provides a detailed, comprehensive view of the literature comparing the clinical utility of various assessment modalities. Furthermore, there is no consensus on the optimal assessment algorithm for peripheral nerve injuries.

Methods

We performed a literature review using a comprehensive combination of keywords and search algorithm. The search was focused on clinical data regarding the assessment of peripheral nerves Results: This review may help to determine the appropriate tools that are currently available for monitoring nerve function both pre and postoperatively. Additionally, the review demonstrates possible roles and areas of improvement for each tool used to assess motor function.

Conclusion

As surgeons work to improve treatments for peripheral nerve injury and dysfunction, identifying the most appropriate existing measures of success and future directions for improved algorithms could lead to improved patient outcomes.

Use of Neuromuscular Ultrasound in the Diagnosis of Disulfiram Polyneuropathy

ABSTRACT

We present the case of a 37-year-old woman with alcohol use disorder, who developed leg cramping, bilateral foot drop, and hand weakness 3 months after starting disulfiram. This was accompanied by an 18-pound involuntary weight loss. Electrophysiologic findings showed a motor predominant axonal neuropathy. Neuromuscular ultrasound showed normal to small cross-sectional area of all nerves studied. This case is discussed, and the ultrasound findings are compared with another reported case.

Moderner Ultraschall in der Diagnostik Neuromuskulärer Erkrankungen

Der neuromuskuläre Ultraschall hat sich in den letzten Jahren zu einem festen Bestandteil in der neurologischen Diagnostik entwickelt. Dazu tragen auch die fortwährende technische Weiterentwicklung der Methode und ihr unkomplizierter und nebenwirkungsfreier Einsatz direkt am Patienten bei. Im klinischen Alltag wird der Ultraschall in der Diagnostik und Differentialdiagnostik sowie in der Verlaufskontrolle traumatischer Nervenläsionen, sekundärer und dynamischer nervaler Kompressionssyndrome, hereditärer und akuter sowie chronisch autoimmuner Polyneuropathien, Motoneuron- und Muskelerkrankungen verwendet. Dabei spielt die Ultraschalldiagnostik auch zunehmend eine Rolle für Therapieentscheidungen, v.a. im Hinblick auf die operative Versorgung und den Einsatz oder die Fortführung immunmodulatorischer Medikamente. In den nächsten Jahren ist eine weitere interdisziplinäre Verbreitung und fortwährend zunehmende Standardisierung der Methode zu erwarten.

Anatomy of the nerves, vessels, and muscular compartments of the forearm, as revealed by high-resolution ultrasound. Part 1: overall structure and forearm compartments

In recent decades, high-resolution ultrasound (HRUS) has revolutionized the morphological and structural evaluation of peripheral nerves and muscles, revealing details of the internal structure of the neural fascicles and muscle architecture. Applications range from diagnostics to interventional procedures. The anatomy of the forearm region is complex, with several muscles and an extensive network of vessels and nerves. To guarantee the success of the evaluation by HRUS, knowledge of the normal anatomy of the region is essential. The aim of these two companion articles is to present the normal anatomy of the nerves and compartments of the forearm, as revealed by HRUS, as well as the relationships between the main vessels and nerves of the region. Part 1 aims to review the overall structure of nerves, muscles and tendons, as seen on HRUS, and that of the forearm compartments. We present a practical approach, with general guidelines and tips on how best to perform the study. Part 2 is a pictorial essay about compartment vascularization and cutaneous innervation. Knowledge of the normal anatomy of the forearm improves the technical quality of the examinations, contributing to better diagnoses, as well as improving the performance and safety of interventional procedures.

Cross-Sectional Area Reference Values for Sonography of Peripheral Nerves in Taiwanese Adults

Background: Neuromuscular ultrasound is a complementary technology that aids in the diagnosis of peripheral neuropathy. The interpretation of neuromuscular ultrasound results requires the use of accurate normative cross-sectional area (CSA) reference values. This study aims to provide CSA reference values specific to Taiwanese adults for Sonography of peripheral nerves in the upper and lower extremities.

Methods: The study cohort included 66 healthy subjects (36 women; 30 men). A linear probe was used to measure the CSA of the median, ulnar, radial, tibial, sural, and peroneal nerves at multiple sites. These data were analyzed to determine standard ranges for the CSA at each site (reference range = mean ± 2 × SD) and identify correlations between the CSA and patient characteristics.

Results: Normative CSA ranges were determined for all the assessed nerve sites, revealing that the nerve sizes in this Taiwanese population were smaller than Caucasian populations but comparable to those reported for other Asian cohorts. Men tended to have larger nerves than women, even after adjusting for height and weight. The size of ulnar nerve in the cubital tunnel and the peroneal nerve in the popliteal fossa correlated negatively with increasing age. The nerve size correlated positively with increasing weight and BMI at several sites, correlation of median nerve in the forearm with weight and BMI was significant after multiple testing. Significant correlation was also found between size of ulnar nerve in cubital tunnel and decreasing height.

Conclusion: We provide reference ranges for neuromuscular ultrasound CSA values for the upper and lower extremities that are specific to the Taiwanese population. These reference values may be useful for evaluating peripheral neuropathy in Taiwanese subjects.

Techniques for Imaging Vascular Supply of Peripheral Nerves

Few studies have been developed to map the vascular structures feeding peripheral nerves, with the majority using cadaveric models and inadequate sample sizes. Preliminary evidence, while limited, indicates that the mapping of these vessels may allow or preclude certain procedures in nerve reconstruction due to the location of essential arterial inflow to the vasa nervorum. This review evaluates the evidence regarding historical, current, and emerging techniques for visualizing these vascular structures in vivo and considers their potential application in peripheral nerve vasculature.