Cross-sectional area reference values for nerve ultrasonography

Median Nerve Shear Wave Elastography Is Associated With the Neurophysiological Severity of Carpal Tunnel Syndrome

OBJECTIVES

This study examines the associations between the median nerve (MN) shear wave elastography (SWE), the MN cross-sectional area (CSA), patient's symptoms, and the neurophysiological severity of carpal tunnel syndrome (CTS). The most appropriate site to perform SWE was also tested.

METHODS

This prospective study comprised 86 wrists of 47 consecutive patients who volunteered for MN ultrasound after an electrodiagnostic study. The neurophysiological severity of CTS was assessed according to the results of a nerve conduction study (NCS). The MN CSA was measured at the carpal tunnel inlet (wCSA) and the forearm (fCSA). SWE was performed on the MN in a longitudinal orientation at the wrist crease (wSWE), at the forearm (fSWE), and within the carpal tunnel (tSWE).

RESULTS

The wCSA and wSWE correlated positively with the neurophysiological severity of CTS (r = .619, P < .001; r = .582, P < .001, respectively). The optimal cut-off values to discriminate the groups with normal NCS and with findings indicating CTS were 10.5 mm2 for the wCSA and 4.12 m/s for the wSWE. With these cut-off values, wCSA had a sensitivity of 80% and specificity of 87% and wSWE a sensitivity of 88% and specificity of 76%. Neither tSWE nor fSWE correlated with the neurophysiological severity of CTS or differed between NCS negative and positive groups (P = .429, P = .736, respectively).

CONCLUSION

Shear wave velocity in the MN at the carpal tunnel inlet increases in CTS and correlates to the neurophysiological CTS severity equivalently to CSA measured at the same site.

Assessment of traumatic mandibular nerve using MR neurography sequence: a preliminary study

BACKGROUND

Iatrogenic mandibular nerve damage resulting from oral surgeries and dental procedures is painful and a formidable challenge for patients and oral surgeons alike, mainly because the absence of objective and quantitative methods for diagnosing nerve damage renders treatment and compensation ambiguous while often leading to medico-legal disputes. The aim of this study was to examine discriminating factors of traumatic mandibular nerve within a specific magnetic resonance imaging (MRI) protocol and to suggest tangible diagnostic criteria for peripheral trigeminal nerve injury.

METHODS

Twenty-six patients with ipsilateral mandibular nerve trauma underwent T2 Flex water, 3D short tau inversion recovery (STIR), and diffusion-weighted imaging (DWI) acquired by periodically rotating overlapping parallel lines with enhanced reconstruction (PROPELLER) pulse sequences; 26 injured nerves were thus compared with contra-lateral healthy nerves at anatomically corresponding sites. T2 Flex apparent signal to noise ratio (FSNR), T2 Flex apparent nerve-muscle contrast to noise ratio (FNMCNR) 3D STIR apparent signal to noise ratio (SSNR), 3D STIR apparent nerve-muscle contrast to noise ratio (SNMCNR), apparent diffusion coefficient (ADC) and area of cross-sectional nerve (Area) were evaluated.

RESULTS

Mixed model analysis revealed FSNR and FNMCNR to be the dual discriminators for traumatized mandibular nerve (p < 0.05). Diagnostic performance of both parameters was also determined with area under the receiver operating characteristic curve (AUC for FSNR = 0.712; 95% confidence interval [CI]: 0.5660, 0.8571 / AUC for FNMCNR = 0.7056; 95% confidence interval [CI]: 1.011, 1.112).

CONCLUSIONS

An increase in FSNR and FNMCNR within our MRI sequence seems to be accurate indicators of the presence of traumatic nerve. This prospective study may serve as a foundation for sophisticated model diagnosing trigeminal nerve trauma within large patient cohorts.

Diagnostic accuracy of ultrasound and MR imaging in peroneal neuropathy: A prospective, single-center study

INTRODUCTION/AIMS

Magnetic resonance imaging (MRI) findings in peroneal neuropathy are not well documented and the prognostic value of imaging remains uncertain. Upper limits of cross-sectional area (CSA) on ultrasound (US) have been established, but uncertainty regarding generalizability remains. We aimed to describe MRI findings of the peroneal nerve in patients and healthy controls and to compare these results to US findings and clinical characteristics.

METHODS

We prospectively included patients with foot drop and electrodiagnostically confirmed peroneal neuropathy, and performed clinical follow-up, US and MRI of both peroneal nerves. We compared MRI findings to healthy controls. Two radiologists evaluated MRI features in an exploratory analysis after images were anonymized and randomized.

RESULTS

Twenty-two patients and 38 healthy controls were included. Whereas significant increased MRI CSA values were documented in patients (mean CSA 20 mm2 vs. 13 mm2 in healthy controls), intra- and interobserver variability was substantial (variability of, respectively, 7 and 9 mm2 around the mean in 95% of repeated measurements). A pathological T2 hyperintense signal of the nerve was found in 52.6% of patients (50% interobserver agreement). Increased CSA measurements (MRI/US), pathological T2 hyperintensity of the nerve and muscle edema were not predictive for recovery.

DISCUSSION

Imaging is recommended in all patients with peroneal neuropathy to exclude compressive intrinsic and extrinsic masses but we do not advise routine MRI for diagnosis or prediction of outcome in patients with peroneal neuropathy due to high observer variability. Further studies should aim at reducing MRI observer variability potentially by semi-automation.

Updates in diagnostic tools for diagnosing nerve injury and compressions

Predicting prognosis after nerve injury and compression can be challenging, even for the experienced clinician. Although thorough clinical assessment can aid diagnosis, we cannot always be precise about long-term functional recovery of either motor or sensory nerves. To evaluate the severity of nerve injury, surgical exploration remains the gold standard, particularly after iatrogenic injury and major nerve injury from trauma, such as brachial plexus injury. Recently, advances in imaging techniques (ultrasound, magnetic resonance imaging [MRI] and MR neurography) along with multimodality assessment, including electrodiagnostic testing, have allowed us to have a better preoperative understanding of nerve continuity and prediction of nerve health and possible recovery. This article outlines the current and potential roles for clinical assessment, exploratory surgery, electrodiagnostic testing ultrasound and MRI in entrapment neuropathies, inflammatory neuritis and trauma. Emphasis is placed on those modalities that are improving in diagnostic accuracy of nerve assessment before any surgical intervention.

A prospective case series to evaluate subcostal nerve injury with high-resolution ultrasound in posterior retroperitoneoscopic adrenalectomy

BACKGROUND

Posterior retroperitoneoscopic adrenalectomy has several advantages over transabdominal laparoscopic adrenalectomy regarding operating time, blood loss, postoperative pain, and recovery. However, postoperatively several patients report chronic pain or hypoesthesia. We hypothesized that these symptoms may be the result of damage to the subcostal nerve, because it passes the surgical area.

METHODS

A prospective single-center case series was performed in adult patients without preoperative pain or numbness of the abdominal wall who underwent unilateral posterior retroperitoneoscopic adrenalectomy. Patients received pre- and postoperative questionnaires and a high-resolution ultrasound scan of the subcostal nerve and abdominal wall muscles was performed before and directly after surgery. Clinical evaluation at 6 weeks was performed with repeat questionnaires, physical examination, and high-resolution ultrasound. Long-term recovery was evaluated with questionnaires, and photographs from the patients were examined for abdominal wall asymmetry.

RESULTS

A total of 25 patients were included in the study. There were no surgical complications. Preoperative visualization of the subcostal nerve was possible in all patients. At 6 weeks, ultrasound showed nerve damage in 15 patients, with no significant association between nerve damage and postsurgical pain. However, there was a significant association between nerve damage and hypoesthesia (p = 0.01), sensory (p < 0.001), and motor (p < 0.001) dysfunction on physical examination. After a median follow-up of 18 months, 5 patients still experienced either numbness or muscle weakness, and one patient experienced chronic postsurgical pain.

CONCLUSION

In this exporatory case series the incidence of postoperative damage to the subcostal nerve, both clinically and radiologically, was 60% after posterior retroperitoneoscopic adrenalectomy. There was no association with pain, and the spontaneous recovery rate was high.

Is Ultrasonography a Reliable Approach for the Evaluation of Carpal Tunnel Syndrome in Patients With Mucopolysaccharidosis?

BACKGROUND

One of the most common causes of carpal tunnel syndrome (CTS) in childhood is mucopolysaccharidosis (MPS). While ultrasonography (US) can aid in the diagnosis of CTS in adult patients, there is limited experience of this in the pediatric group. We aimed to investigate the results of wrist ultrasonography, which may be a candidate alternative to electrophysiological examination.

METHODS

The participants were evaluated for symptoms, physical examination findings, electrophysiological tests and grayscale US. CTS was diagnosed in accordance with the American Academy of Orthopedic Surgeons Management of Carpal Tunnel Syndrome: Evidence-Based Clinical Practice Guideline.

RESULTS

Included in the study were 27 MPS patients aged 4.5-32 years and 30 healthy control subjects aged 4.3-26 years. Of the 54 wrists in the MPS group, 30 were diagnosed with CTS. The median cross-sectional area (CSA) at the proximal carpal tunnel, the CSA at the forearm, and the wrist-forearm ratio (WFR) were higher in the wrists of the MPS with CTS group than in those without CTS and the healthy control subjects. The WFR cutoff of ≥1.35, 56.6% (95% CI: 437.4-74.5) sensitivity, and 89.8% (95% CI: 81.0-95.5) specificity were consistent with a diagnosis of CTS (receiver operating characteristics analysis, area under the curve = 0.775, 95% CI: 0.673-0.877).

CONCLUSION

Although the US provides results with unsatisfactory specificity and sensitivity, it is a candidate for further investigation for the diagnosis of CTS because it is an innovative, noninvasive, and more accessible method. WFR value may produce more meaningful results than wrist or forearm nerve area measurements.

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.

The emotion paradox in the aging body and brain

With age, parasympathetic activity decreases, while sympathetic activity increases. Thus, the typical older adult has low heart rate variability (HRV) and high noradrenaline levels. Younger adults with this physiological profile tend to be unhappy and stressed. Yet, with age, emotional experience tends to improve. Why does older adults' emotional well-being not suffer as their HRV decreases? To address this apparent paradox, I present the autonomic compensation model. In this model, failing organs, the initial phases of Alzheimer's pathology, and other age-related diseases trigger noradrenergic hyperactivity. To compensate, older brains increase autonomic regulatory activity in the pregenual prefrontal cortex (PFC). Age-related declines in nerve conduction reduce the ability of the pregenual PFC to reduce hyperactive noradrenergic activity and increase peripheral HRV. But these pregenual PFC autonomic compensation efforts have a significant impact in the brain, where they bias processing in favor of stimuli that tend to increase parasympathetic activity (e.g., stimuli that increase feelings of safety) and against stimuli that tend to increase sympathetic activity (e.g., threatening stimuli). In summary, the autonomic compensation model posits that age-related chronic sympathetic/noradrenergic hyperactivity stimulates regulatory attempts that have the side effect of enhancing emotional well-being.

Neuromuscular ultrasound changes in unilateral symptomatic subacute lumbosacral radiculopathy: A prospective simple blinded cohort study

INTRODUCTION/AIMS

Lumbosacral radiculopathy (LR) is a common disorder. Neuromuscular ultrasound (NMU) is a rapidly evolving technique for the investigation of peripheral nerve and muscle disorders, but studies using NMU in LR are lacking. The aim of the present study was to investigate ultrasonographic neuromuscular changes distant from root compression in patients with subacute to chronic compressive LR with motor impairment.

METHODS

Patients with unilateral subacute to chronic L4, L5, or S1 radiculopathy with motor impairment and confirmed by magnetic resonance imaging were included. The sciatic and femoral nerve cross-sectional areas (CSA), the CSA of lower limb muscles, and muscle fasciculation detection rate were assessed using a pre-specified neuromuscular ultrasound evaluation with blinded side-to-side comparison.

RESULTS

Of the 18 included patients, 66% were male and the mean age was 51 years. Overall, 16.7% had L4, 55.5% L5, and 27.8% S1 radiculopathy, mostly due to disc herniation (83%). Sciatic nerve CSA of the symptomatic side was increased (61.4 mm2 vs. 51.3 mm2; p = .001), and the fasciculation detection rate was higher in the affected muscles (delta = 13%, p = .007) compared to unaffected ones. Muscle CSA in affected and nonaffected muscles was decreased on the symptomatic side.

DISCUSSION

NMU evaluation in patients with symptomatic subacute to chronic LR revealed sciatic nerve enlargement distant from nerve root compression and higher fasciculation rates. These structural findings on NMU might be due to an axonal repair mechanism and an inflammatory response with endoneurial edema induced by ongoing nerve damage and potentially reflect progressive axonal loss.

Neuromuscular ultrasound findings in gunshot wounds

INTRODUCTION/AIMS

A spectrum of peripheral nerve injuries is associated with gunshot wounds (GSWs). Due to Wallerian degeneration, distal nerve lesions may go undetected on electrodiagnostic (EDX) testing. In patients with GSW undergoing high-resolution ultrasound (HRUS) for evaluation of neurological deficits, we have observed distal nerve morphological changes, but these have not been systematically studied. The aim of this study was to characterize changes on HRUS in nerves at and distal to gunshot injuries and to identify the frequency with which these changes occur.

METHODS

A retrospective cohort study was performed on patients referred for HRUS with peripheral nerve injuries from GSW. The primary injured nerve(s) were assessed along with distal segments of the same nerve and those of adjacent nerves. Findings were also compared to EDX studies.

RESULTS

Twenty-two of the 28 nerves injured proximally by GSW were evaluated distally and of these, 68% showed abnormal ultrasound findings, including enlarged cross sectional area (59%), fascicular enlargement (50%), and decreased nerve echogenicity (59%). In 17 patients, adjacent nerves were evaluated and 8 of the patients (47%) showed abnormalities in at least one distal adjacent nerve, including enlarged cross sectional area (41%), fascicular enlargement (41%), and decreased nerve echogenicity (35%).

DISCUSSION

This study demonstrated morphological changes at the site of the GSW but also in distal nerve segments including nerve enlargement, fascicular enlargement, and changes in nerve echogenicity. The complementary use of HRUS with EDX was highlighted in evaluation of GSW victims to assess the extent of peripheral nerve injury.

Convolutional Neural Network Approaches in Median Nerve Morphological Assessment from Ultrasound Images

Ultrasound imaging has been used to investigate compression of the median nerve in carpal tunnel syndrome patients. Ultrasound imaging and the extraction of median nerve parameters from ultrasound images are crucial and are usually performed manually by experts. The manual annotation of ultrasound images relies on experience, and intra- and interrater reliability may vary among studies. In this study, two types of convolutional neural networks (CNNs), U-Net and SegNet, were used to extract the median nerve morphology. To the best of our knowledge, the application of these methods to ultrasound imaging of the median nerve has not yet been investigated. Spearman's correlation and Bland-Altman analyses were performed to investigate the correlation and agreement between manual annotation and CNN estimation, namely, the cross-sectional area, circumference, and diameter of the median nerve. The results showed that the intersection over union (IoU) of U-Net (0.717) was greater than that of SegNet (0.625). A few images in SegNet had an IoU below 0.6, decreasing the average IoU. In both models, the IoU decreased when the median nerve was elongated longitudinally with a blurred outline. The Bland-Altman analysis revealed that, in general, both the U-Net- and SegNet-estimated measurements showed 95% limits of agreement with manual annotation. These results show that these CNN models are promising tools for median nerve ultrasound imaging analysis.

The role of imaging in focal neuropathies

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Axillary and musculocutaneous neuropathies

This chapter covers axillary and musculocutaneous neuropathies, with a focus on clinically relevant anatomy, electrodiagnostic approaches, etiologic considerations, and management principles. Disorders of the lateral antebrachial cutaneous nerve, a derivative of the musculocutaneous nerve, are also reviewed. We emphasize the importance of objective findings, including the physical examination and electrodiagnostic evaluation in confirming the isolated involvement of each nerve which, along with the clinical history, informs etiologic considerations. Axillary and musculocutaneous neuropathies are both rare in isolation and most frequently occur in the setting of trauma. Less commonly encountered etiologies include external compression or entrapment, neoplastic involvement, or immune-mediated disorders including neuralgic amyotrophy, postsurgical inflammatory neuropathy, multifocal motor neuropathy, vasculitic neuropathy, and multifocal chronic inflammatory demyelinating polyradiculoneuropathy.

Unveiling the power of imaging techniques: comparing high-resolution ultrasound and functional MR neurography in peripheral nervous system pathology: a short communication

MRI and ultrasonography are used for diagnosing and helping manage peripheral nervous system pathologies. Multiple studies have compared the diagnostic accuracy of these two modalities, but the results can vary depending on the specific conditions being evaluated. In general, high-resolution ultrasound is considered a reliable and accurate tool for evaluating peripheral nerves, with high sensitivity and specificity. High-resolution ultrasound and functional MR neurography are both noninvasive imaging techniques used to evaluate nerve structures in the body. However, they differ in several technical aspects like imaging modality, spatial resolution, field of view, image quality, and accessibility. Establishing consensus on image acquisition techniques, and reporting formats to facilitate effective communication and comparison of results will further enhance the outcomes. The use of advanced ultrasound techniques, such as contrast-enhanced ultrasound, elastography, and ultrasound biomicroscopy, should be promoted for better visualization and characterization of nervous tissues, like transcranial Doppler for cerebrovascular evaluation.

Neuromuscular ultrasound in leprosy: A scanning protocol

The diagnosis of leprosy neuropathies has been traditionally based on clinical findings and electrodiagnostic studies, but ultrasound has emerged as a new tool for use in clinical practice. We conducted a literature search on the subject and developed a pragmatic ultrasound scanning protocol for patients with confirmed or suspected leprosy neuropathy. We suggest scanning the ulnar, median, superficial radial, common fibular and sural nerves at specific sites and assessing cross-sectional area, vascularity, and epineural thickness. Our protocol is potentially useful in differentiating leprosy neuropathies from other demyelinating neuropathies, but its applicability and accuracy must be evaluated in different centers.

Ultrasound morphometry of the cervical vagus nerve for daily clinical practice: Reference values for cross sectional area and fascicle count

INTRODUCTION

High resolution ultrasound (US) of the cervical vagus nerve (CVN) is clinically relevant in the diagnostic workup and during neurostimulation therapy of several neurologic diseases. This prospective study aims to provide reference data of the cross-sectional area (CSA) and fascicle count of the normal CVN and to investigate their possible association with anthropometric data in a large cohort of patients.

METHODS

A total of 657 CVNs in 330 individuals without history of neurological disease were examined using US (7-15Mhz). The CVN fascicle count and CSA inside the hyperechoic epineurium at the level of the thyroid lobes were measured. Three CSA measurements were performed to calculate the mean value. Anthropometric data were recorded.

RESULTS

The mean fascicle count was 2.4 ± 1.1 (right) and 2 ± 1 (left) (paired t- test, p < 0.001). Two CVN patterns were identified: A single hypoechoic fascicular structure (26.2 % right, 36.3 % left) and a honeycomb structure of 2-6 discrete fascicles (72.3 % right, 63.7 % left). Right CVN mean CSA was larger compared to left (2.3 ± 1 mm2 and 1.8 ± 0.8 mm2 respectively, t-test, p-0.000). There was no difference in the CSA values between sex and no correlation to age or height. A positive correlation between the CSA and weight and BMI was found (Pearson's correlation, p = 0.01 right and p = 0.05 left).

CONCLUSION

The right CVN has larger CSA and contains more fascicles than the left. CVN is usually mono- or oligo-fascicular with a honeycomb appearance. The CSA increased with increasing BMI but no age and sex specific differences were noted.

Normative Reference Values of the Tibial Nerve in Healthy Individuals Using Ultrasonography: A Systematic Review and Meta-Analysis

BACKGROUND

High-resolution ultrasound of the tibial nerve has been used for screening of several neurologic disorders, but normative reference values of tibial nerve cross-sectional areas (CSA) have not been well established. Thus, the present meta-analysis was performed to generate normative estimates of tibial nerve CSA at various sites of the lower limb based on ultrasonography.

METHODS

Google Scholar, Scopus and PubMed were searched for potential studies. Studies were required to report tibial nerve CSA in healthy individuals to be included. A random-effect meta-analysis was performed to calculate tibial nerve CSA values. Subgroup and statistical analyses were performed to study covariates.

RESULTS

Forty-eight eligible articles consisting of 2695 limbs were included. The average tibial nerve CSA was found to be 10.9 mm2 at the ankle (95% CI: 9.9-11.8) and should not exceed 11.8 mm2 in healthy adults. At the popliteal fossa, the overall CSA was 21.7 mm2 (95% CI: 17.5-25.8) in healthy adults. At both sites, the average tibial nerve CSA was significantly larger in adults than in children, and the differences by geographical region were not statistically significant. At the ankle, tibial nerve CSA increased with age and body mass index, while at the popliteal fossa it increased with age and weight.

CONCLUSIONS

our findings indicate that the tibial nerve varied not only along its course but also among sub-variables. Establishing normal references values of tibial nerve CSA is helpful to differentiate healthy from diseased tibial nerves such as in diabetic peripheral neuropathy or tarsal tunnel syndrome.

Nerve ultrasound reference values in children and adolescents: Echogenicity and influence of anthropometric factors including hand volume

Background

Nerve cross-sectional area (CSA) reference values in high-resolution ultrasound for children and adolescents are influenced by demographic and anthropometric factors such as age, height and weight.

Objectives

The influence of hand volume as an additional morphometric factor was evaluated and nerve echogenicity was analyzed in a prospective cross-sectional study.

Methods

CSA were measured in 30 healthy children and adolescents from 2 to 17 years in the median, ulnar, radial, tibial, peroneal and sural nerves. Height, weight, age, handedness and gender were recorded, the volume of the hands was measured using the water displacement method. The intra-nerve CSA variability (INV), left/right ratios and absolute differences were calculated. Age groups were compared by the Kruskal-Wallis test. The influence of demographic factors was analyzed using Spearman correlation and multiple linear regression. Echogenicity and fraction of black were determined for each nerve segment.

Results

Nerve CSA values were consistently lower than those reported for adults and correlated in all measured nerve sites with age, height, weight and hand volume. Weight showed the highest correlation coefficient (R = .95) with the best fitting model predicting CSA. Correlation coefficients were higher in a linear than in a logarithmic model. Ratios were stable, the absolute differences increased with age and were significantly different between age groups. Most nerves showed a mixed or hypoechogenic pattern in echogenicity analysis, hyperechogenicity is less frequently observed.

Conclusions

Nerve CSA in children and adolescents is lower than in adults and increases proportionally during growth with a constant INV and left/right ratio in different age groups. Weight and age are predominant anthropometric factors predicting nerve size. Hand volume is correlated with nerve size, but does not predict CSA independently. Echogenicity can provide additional information on nerve structure.

Cross-sectional area and echo intensity values of peripheral nerves: Ultrasonographic and cadaveric correlation

Introduction

Ultrasonography allows high-resolution visualisation of the peripheral nerves for quantitative and qualitative analyses. We report cross-sectional area values (quantitative measure) and echo intensity values (qualitative measure) for 46 peripheral nerve sites in upper and lower extremities in cadaveric specimens.

Objective

To determine cross-sectional area values and echo intensity values of peripheral nerves of upper and lower extremities at 46 nerve sites.

Methods

Nerve measurements were obtained using electronic callipers and ultrasonography for linear dimension and cross-sectional area measurements, respectively, in six cadaveric specimens for 46 peripheral nerve sites. Ultrasound images were further analysed to estimate echo intensity percentage values for 46 nerves.

Results

We present normal cross-sectional area values of various nerves of upper and lower extremities with their respective echo intensity values. Calculated cross-sectional area values from linear dimensions did not match the measured cross-sectional area values via trace method.

Conclusion

Cross-sectional area values (quantitative measure) and echo intensity values (qualitative measure) for 46 peripheral nerve sites in upper and lower extremities in cadaveric specimens are presented. The estimation of cross-sectional area via linear measurement is not a good approximation of the cross-sectional area (cross-sectional area measured by trace method on ultrasound image).

Sonographic peripheral nerve cross-sectional area in adults, excluding median and ulnar nerves: A systematic review and meta-analysis

INTRODUCTION/AIMS

Although electromyography remains the "gold standard" for assessing and diagnosing peripheral nerve disorders, ultrasound has emerged as a useful adjunct, providing valuable anatomic information. The objective of this study was to conduct a systematic review and meta-analysis evaluating the normative sonographic values for adult peripheral nerve cross-sectional area (CSA).

METHODS

Medline and Cochrane Library databases were systematically searched for healthy adult peripheral nerve CSA, excluding the median and ulnar nerves. Data were meta-analyzed, using a random-effects model, to calculate the mean nerve CSA and its 95% confidence interval (CI) for each nerve at a specific anatomical location (= group).

RESULTS

Thirty groups were identified and meta-analyzed, which comprised 16 from the upper extremity and 15 from the lower extremity. The tibial nerve (n = 2916 nerves) was reported most commonly, followed by the common fibular nerve (n = 2580 nerves) and the radial nerve (n = 2326 nerves). Means and 95% confidence interval (CIs) of nerve CSA for the largest number of combined nerves were: radial nerve assessed at the spiral groove (n = 1810; mean, 5.14 mm2 ; 95% CI, 4.33 to 5.96); common fibular nerve assessed at the fibular head (n = 1460; mean, 10.18 mm2 ; 95% CI, 8.91 to 11.45); and common fibular nerve assessed at the popliteal fossa (n = 1120; mean, 12.90 mm2 ; 95% CI, 9.12 to 16.68). Publication bias was suspected, but its influence on the results was minimal.

DISCUSSION

Two hundred thirty mean CSAs from 15 857 adult nerves are included in the meta-analysis. These are further categorized into 30 groups, based on anatomical location, providing a comprehensive reference for the clinician and researcher investigating adult peripheral nerve anatomy.

Ultrasonic visualization technique for anatomical and functional analyses of the sciatic nerve in rats

Background and objective

Ultrasound has been widely used in the diagnosis and minimally invasive treatment of peripheral nerve diseases in the clinic, but there is still a lack of feasibility analysis in rodent models of neurological disease. The purpose of this study was to investigate the changes in the cross-sectional area of the sciatic nerve of different genders and body weights and to explore the effectiveness and reliability of an ultrasound-guided block around the sciatic nerve in living rats.

Methods

Using ultrasound imaging anatomy of the sciatic nerve of rats, the cross-sectional area of the sciatic nerve in rats of different genders from 6 to 10 weeks old was calculated, and then analyzed its correlation with body weight. Further analyses were conducted through behavioral and cadaveric studies to evaluate the feasibility of ultrasound-guided perineural injection of the sciatic nerve in rats.

Results

We first reported that the sciatic nerve cross-sectional area of rats was increased with age (F = 89.169, P < 0.001), males had a higher sciatic nerve cross-sectional area than females (F = 60.770, P < 0.001), and there was a positive correlation with body weight (r_Male = 0.8976, P < 0.001; r_Female = 0.7733, P < 0.001). Behavioral observation of rats showed that the lower extremity complete block rate was 80% following the administration of drugs around the sciatic nerve under ultrasound guidance and staining with methylene blue occurred in all sciatic nerves and surrounding muscles and fascia using 20 ultrasound-guided injections.

Conclusions

Ultrasound visualization technology can be used as a new auxiliary evaluation and intervention therapy for animal models of peripheral nerve injury, and will provide overwhelming new references for the basic research of neurological diseases.

Peripheral Nerve Ultrasound for the Differentiation between ALS, Inflammatory, and Hereditary Polyneuropathies

Background and Objectives: Ultrasound (US) is a non-invasive tool for the in vivo detection of peripheral nerve alterations. Materials and Methods: In this study, we applied nerve US to assist the discrimination between the spectrum of amyotrophic lateral sclerosis (ALS, n = 11), chronic inflammatory demyelinating polyradiculoneuropathy (CIDP, n = 5), and genetically confirmed Charcot-Marie-Tooth disease (CMT, n = 5). All participants and n = 15 controls without neurological diseases underwent high-resolution US of the bilateral tibial nerve. The nerve cross-sectional area (CSA) and nerve microvascular blood flow were compared between the groups and related to cerebrospinal fluid (CSF) measures, clinical symptoms, and nerve conduction studies. The analyses are part of a larger multimodal study on the comparison between US and 7 Tesla (7T) magnetic resonance neurography (MRN). Results: The patients and controls were matched with respect to their demographical data. CMT had the longest disease duration, followed by CIDP and ALS. CSA was related to age, weight, and disease duration. CSA was larger in CMT and CIDP compared to ALS and controls. The blood flow was greatest in CIDP, and higher than in CMT, ALS, and controls. In ALS, greater CSA was correlated with greater CSF total protein and higher albumin quotient. The US measures did not correlate with clinical scores or nerve conduction studies in any of the subgroups. Conclusion: Our results point towards the feasibility of CSA and blood flow to discriminate between ALS, CIDP, and CMT, even in groups of small sample size. In ALS, larger CSA could indicate an inflammatory disease subtype characterized by reduced blood-nerve barrier integrity. Our upcoming analysis will focus on the additive value of 7T MRN in combination with US to disentangle the spectrum between more inflammatory or more degenerative disease variants among the disease groups.

Ultrasound of the normal vagus nerve cross-sectional area in the carotid sheath

The aim of this article is to utilize ultrasound to evaluate the normal cross-sectional area (CSA)of the vagus nerve (VN) in the carotid sheath. This study included 86 VNs in 43 healthy subjects (15 men, 28 women); mean age 42.1 years and mean body mass index 26.2 kg/m2. For each subject, the bilateral VNs were identified by US at the anterolateral neck within the common carotid sheaths. One radiologist obtained 3 separate CSA measurements for each of the bilateral VNs with complete transducer removal between each measurement. Additionally, for each participant, demographic information of age and gender as well as body mass index, weight, and height were documented. The mean CSA of the right VN in the carotid sheath was 2.1 and 1.9 mm2 for the left VN. The right VN CSA was significantly larger than the left VN (P < .012). No statistically significant correlation was noted in relation to height, weight, and age. We believe that the reference values for the normal CSA of the VN obtained in our study, could help in the sonographic evaluation of VN enlargement, as it relates to the diagnosis of various diseases affecting the VN.

Correlation between age and the sciatic nerve diameter in the first 2 years of life: A high-resolution ultrasound study

AIM

To investigate the maturation of the peripheral nervous system by analyzing the cross-sectional area of the sciatic nerve during the first 2 years of life.

METHODS

The sciatic nerve was examined by high-resolution ultrasound imaging in 52 children aged 0 days to 10 years, 45 of whom were younger than 2 years. The correlation between the cross-sectional area of the nerve and the age was statistically tested. A logarithmic regression analysis was performed to develop a logarithmic growth model of the cross-sectional area.

RESULTS

There is a highly significant correlation between the age and the cross-sectional area of the sciatic nerve. The growth rate can well be described by a logarithmic model.

INTERPRETATION

Based on the literature on the maturation of the median nerve and nerve roots and the findings of the present study, we conclude that both the proximal and the distal parts of the nerves of the peripheral nervous system increase simultaneously.

WHAT THIS PAPER ADDS

Normative values for the size of the sciatic nerve in children.

Ultrasound-based neuropathy diagnosis in COVID-19 patients in post-intensive care rehabilitation settings. A retrospective observational study

OBJECTIVES

using ultrasound scanning to examine the correlation between increase of Common Fibular Nerve's (CFN) Cross Sectional Area (CSA) and functional impairment of foot dorsiflexor muscles as an early sign of peripheral neuropathy.

DESIGN

retrospective observational study.

SETTING

in-patient rehabilitation unit between November 2020 and July 2021.

PARTICIPANTS

26 inpatients who underwent prolonged hospitilization in ICU'S and were diagnosed with CRYMINE after SARS-COV-2 infection. Physical examination and ultrasound scanning of the CFN and EMG/ENG were carried out on each patient.

INTERVENTIONS

not applicable MAIN OUTCOME MEASURE(S): CFN's CSA at the peroneal head.

RESULTS

we verified a significant increase in the CSA of the CFN measured at the peroneal head in more than 90% of the nerves tested. A cut off value of CFN's CSA of 0,20 cm was used to identify pathological nerves. No correlations with other variables (BMI, ICU days) were found.

CONCLUSION

US scanning of the CFN appears to be an early and specific test in the evaluation of CPN's abnormalities in post COVID-19 patients. US scanning is a reproducible, cost effective, safe and easily administered bedside tool to diagnose a loss of motor function when abnormalities in peripheral nerves are present.

Ulnar nerve thickness at the elbow on longitudinal ultrasound view in control subjects

INTRODUCTION

Ulnar mononeuropathy at the elbow is the second most frequent neuropathy in humans. Diagnosis is based on clinical and electrophysiological criteria and, more recently, also on ultrasound. Cross-sectional ultrasound is currently the most valued, although longitudinal ultrasound allows assessment of the entire affected trajectory of the nerve in a single view, but always in a straight line with no changes in direction, as in the extended elbow. The main aim of this work is to propose normative values ​​for longitudinal ultrasound of the ulnar nerve at the elbow.

METHODS

The neurological exploration of upper extremity, and electrophysiological and ultrasound parameters at the elbow of ulnar nerve were evaluated in 76 limbs from 38 asymptomatic subjects.

RESULTS

The diameters of the nerve as well as the distal and proximal areas were larger at the proximal region of the ulnar groove, and even more so in older individuals. In most of these elderly subjects, we found a small, non-significant slowdown in motor conduction velocity at the elbow with respect to the forearm (less than 5 m/s).

CONCLUSIONS

We observed a good correlation between the longitudinal and cross-sectional ultrasounds of the ulnar nerve at the elbow. Longitudinal ultrasound proved to be sensitive, reliable, simple and rapid, but its greatest contribution was allowing the visualization of the entire nerve trajectory in an integrated way, providing an image with good definition of the outline, proportions and intraneural characteristics of the nerve.

Comparing the accuracy of ultrasound-based measurements of the cervical vagus nerve

Vagus nerve stimulation (VNS) has become a promising therapy especially for drug resistant epilepsy and other pathologies. Side effects or missing therapeutic success are observed due to cuff electrodes that are too narrow or too wide. Preoperative high-resolution ultrasound is used to evaluate the size of the cervical vagus nerve (CVN) to estimate the size of cuff electrodes for VNS. It remains unclear how precise ultrasound reflects the CVN dimensions, which has been the objective of this study. CVN cross-sections and diameters were investigated in 23 sides from 12 bodies, using ultrasound, histology, and CVN casting in situ as a reference. Morphometric data were obtained including fascicle count and nerve composition in histology. CVN yielded significant side-, age-, and BMI-related differences. CVN cross-sections were smaller in ultrasound when compared to casting and histology (1.5 ± 0.4 vs. 3.1 ± 0.9 vs. 2.3 ± 0.7 mm²). With the given setting in ultrasound, CVN cross-sections were consistently underestimated when compared to casting. Ultrasound-based cross-section measurements are related to a biased estimation of CVN size. A factor to correct for method related differences may help to adjust for accurate cuff electrode sizes for patient needs and to reduce undesired effects and potentially material consumption.

Ultrasound evaluation of vagus nerve cross-sectional area in a community-dwelling elderly Japanese cohort

OBJECTIVES

Although the vagus nerve (VN) is easily observed by ultrasonography, few studies have evaluated the cross-sectional area (CSA) of the VN in healthy older individuals from East Asia. In this study, we aimed to report reference values for the CSA of the VN in community-dwelling elderly Japanese individuals and to identify any associated medical history and/or lifestyle factors.

METHODS

The present study included 336 participants aged ≥ 70 years from a prospective cohort study conducted in Yahaba, Japan from October 2021 to February 2022. The CSA of the VN was measured bilaterally at the level of the thyroid gland by ultrasonography. Simple linear regression analysis and generalized estimating equation were conducted to identify the associations between clinical and background factors and the CSA of the VN.

RESULTS

In our cohort, the median CSA of the VN was 1.3 mm2 (interquartile range [IQR] 1.1-1.6) on the right side and 1.2 mm2 (IQR 1.0-1.4) on the left side. Generalized estimating equation showed that history of head injury (β = 0.19, p < .01), current smoking habit (β = -0.09, p = .03), and BMI (β = 0.02, p < .01) were independently associated with the CSA of the VN.

CONCLUSION

We have reported reference VN CSA values for community-dwelling elderly Japanese individuals. In addition, we showed that the CSA of the VN was positively associated with a history of head injury and BMI and inversely associated with current smoking habit.

Evidence of nerve hypertrophy in patients with inclusion body myositis on lower limb MRI

INTRODUCTION/AIMS

Inclusion body myositis (IBM) is a myopathic condition but in some patients has been associated with an axonal length-dependent polyneuropathy. In this study, we quantified the cross-sectional area of the sciatic and tibial nerves in patients with IBM comparing with Charcot-Marie-Tooth disease type 1A (CMT1A) and healthy controls using magnetic resonance neurography (MRN).

METHODS

MRN of the sciatic and tibial nerves was performed at 3T using MPRAGE and Dixon acquisitions. Nerve cross-sectional area (CSA) was measured at the mid-thigh and upper third calf regions by an observer blinded to the diagnosis. Correlations were performed between these measurements and clinical data.

RESULTS

A total of 20 patients with IBM, 20 CMT1A and 29 healthy controls (age- and sex-matched) were studied. Sciatic nerve CSA was significantly enlarged in patients with IBM and CMT1A compared to controls (sciatic nerve mean CSA 62.3 ± 22.9 mm² (IBM) vs. 35.5 ± 9.9 mm² (controls), p < 0.001; and 96.9 ± 35.5 mm² (CMT1A) vs. 35.5 ± 9.9 mm² (controls); p < 0.001). Tibial nerve CSA was also enlarged in IBM and CMT1 patients compared to controls.

DISCUSSION

MRN reveals significant hypertrophy of the sciatic and tibial nerves in patients with IBM and CMT1A compared to controls. Further studies are needed to correlate with neurophysiological measures and assess whether this finding is useful diagnostically.

Cross-Sectional Area of the Tibial Nerve in Diabetic Peripheral Neuropathy Patients: A Systematic Review and Meta-Analysis of Ultrasonography Studies

Background: There is a link between diabetic peripheral neuropathy (DPN) progression and the increase in the cross-sectional area (CSA) of the tibial nerve at the ankle. Nevertheless, no prior meta-analysis has been conducted to evaluate its usefulness for the diagnosis of DPN. Methods: We searched Google Scholar, Scopus, and PubMed for potential studies. Studies had to report tibial nerve CSA at the ankle and diabetes status (DM, DPN, or healthy) to be included. A random-effect meta-analysis was applied to calculate pooled tibial nerve CSA and mean differences across the groups. Subgroup and correlational analyses were conducted to study the potential covariates. Results: The analysis of 3295 subjects revealed that tibial nerve CSA was 13.39 mm2 (CI: 10.94−15.85) in DM patients and 15.12 mm2 (CI: 11.76−18.48) in DPN patients. The CSA was 1.93 mm2 (CI: 0.92−2.95, I2 = 98.69%, p < 0.01) larger than DPN-free diabetic patients. The diagnostic criteria of DPN and age were also identified as potential moderators of tibial nerve CSA. Conclusions: Although tibial nerve CSA at the ankle was significantly larger in the DPN patients, its clinical usefulness is limited by the overlap between groups and the inconsistency in the criteria used to diagnose DPN.

Cross-sectional area reference values for high-resolution ultrasonography of the lower extremity nerves in healthy Korean adults

The cross-sectional area (CSA) reference values of the lower extremity nerves in Asians have been rarely reported. For this study, 107 sex- and age-matched, healthy subjects with a mean age of 46 years (range, 24-75 years) were recruited. All subjects underwent standardized nerve conduction studies of the upper and lower extremities. The CSA was measured unilaterally at 12 sites in the lower extremity nerves, including the femoral, lateral femoral cutaneous, sciatic, common peroneal, superficial peroneal, deep peroneal, tibial, and sural nerves. The CSA significantly correlated with height, weight, and body mass index. The CSA was significantly larger in males than females at most nerves except for the lateral femoral cutaneous, common peroneal (fibular head), and superficial peroneal nerves (distal calf). There was no statistically significant difference between the age groups except for the tibial nerve (ankle). The results of this study provide CSA reference values for the lower extremity nerves including small branches and the values can be useful in the ultrasonographic investigation of various peripheral neuropathies in East Asian populations.

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.

A Retrospective Study of Ultrasound Accuracy for the Diagnosis of Chronic Inflammatory Demyelinating Polyneuropathy

INTRODUCTION

Ultrasound is emerging as a useful tool for the evaluation of immune-mediated neuropathies because it can provide high-resolution anatomic information to complement electrodiagnostic data. Nerve enlargements are commonly found in chronic inflammatory demyelinating polyneuropathy (CIDP), and their presence likely useful in diagnosis, particularly if multifocal.

METHODS

In this study, the authors undertook a retrospective chart review to identify ultrasound findings in patients with CIDP previously studied in a single busy neurodiagnostic laboratory.

RESULTS

Of the 50 cases identified from 2000 to 2017, individuals with a confirmed diagnosis of CIDP (21 cases) were more likely to have multiple sites of enlargement, as well as more pronounced nerve enlargement, than patients who were subsequently found to have an alternate cause of neuropathy (22 cases). The presence of any moderately enlarged nerve segment predicted definite CIDP with sensitivity of 81% and specificity 77%.

CONCLUSION

This study demonstrates that ultrasound can be of diagnostic utility in patients with suspected CIDP, even when conducted in a nonstandardized real-world setting.

Autonomic dysfunction in amyotrophic lateral sclerosis: A neurophysiological and neurosonology study

BACKGROUND AND PURPOSE

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder affecting upper and lower motor neurons. Some ALS patients exhibit concomitant nonmotor signs, and thus ALS is considered a multisystem disorder. The aim of this study is to investigate autonomous nervous system involvement in ALS.

METHODS

We investigated 21 ALS patients and 28 age-matched controls. ALS patients were assessed for disease severity with the Revised-ALS Functional Rating Scale (ALSFSR) and for the presence of autonomic symptoms with the Composite Autonomic Symptom Score scale. Sympathetic nervous system was evaluated by sympathetic skin response (SSR) and parasympathetic nervous system by ultrasonography of vagus nerve (VN) at the level of the thyroid gland.

RESULTS

SSR latencies were shorter and SSR amplitudes were higher in controls compared to ALS patients. The cross-sectional area (CSA) of the VN was significantly smaller in ALS patients (mean CSA right/left: 1.73±0.62 mm² /1.47±0.53 mm² ) compared to controls (mean CSA right/left: 2.91±0.79 mm² /2.30±0.80 mm² ), right: p <. 001, left: p <. 001. There was a significant negative correlation between disease duration and CSA of left-VN (r = -0.493, p = .023). This correlation was attenuated between disease duration and CSA of right-VN (r = -0.419, p = .059). ALSFSR-R was positively correlated to CSA of right-VN (p = .006, r = 0.590). CSA of VN did not correlate with bulbar involvement.

CONCLUSIONS

This study confirms the presence of autonomic dysfunction in ALS patients and provides evidence of VN atrophy that correlates with disease severity and duration and is independent of bulbar involvement. Degeneration of dorsal nucleus neurons of the VN is hypothesized.

Shear wave elastography of the common fibular nerve at the fibular head

ABSTRACT

The aim of this work is to study the sonoelastographic features of the common fibular nerve in healthy adult subjects.This is an observational cross-sectional study. Shear wave elastography was used to evaluate the common fibular nerve. Crosssectional area and stiffness were measured in kilopascal (kPa) and meters/second (m/s).The study included 82 common fibular nerves in 41 healthy adult subjects. The mean cross-sectional area of the common fibular nerve at the fibular head was 8.7 mm2. Positive correlation was noted between stiffness measurements between short and long axes by both methods. The mean stiffness of the common fibular nerve in the short axis was 22.5 kPa, and in the long axis (LA) was 35.4 kPa. Positive correlation was noted between height and stiffness measured by both methods in both axes by kPa. In m/s, the mean stiffness of the common fibular in the short axis was 2.6 m/s, and while in the LA was 3.4 m/s. Height showed positive correlation with both axes for stiff measurements in m\s. Weight showed positive correlation with stiffness measurements by m/s in the LA.The results obtained in our study could be a reference point for evaluating stiffness of the common fibular nerve in research involving different pathologies.

Sonographic Reference Values of Vagus Nerve: A Systematic Review and Meta-analysis

PURPOSE

To establish the first comprehensive and standardized set of vagus nerve (VN) sonographic reference values across all the published studies that can be used to standardize and guide clinical practice and research.

METHODS

This systematic review includes all possible available data from a total of 27 studies and 21 of them were included in the meta-analysis having a total of 864 participants.

RESULTS

The overall mean cross-sectional area ranged from 2.29 to 2.76 mm2 for the right VN and from 1.83 to 2.23 mm2 for the left VN with 95% confidence interval. Sonographic reference values of VN at common carotid artery bifurcation, thyroid gland, and cartilage as well as other anatomic landmarks were provided.

CONCLUSIONS

The mean cross-sectional area of the right VN of 2.53 mm2 and the left one of 2.03 mm2 can be considered as sonographic reference values in healthy adults. This review provides these reference values to be considered in the further sonographic evaluation of VNs.

Ultrasound reference values for peripheral nerve cross-sectional areas and indices in a sample of healthy individuals in Brazil

Objective

To establish peripheral nerve cross-sectional area (CSA) reference values (absolute values, measures of asymmetry, and measures of focality) for healthy individuals in Brazil.

Materials and Methods

Sixty-six healthy volunteers underwent high-resolution ultrasound of the peripheral nerves. We obtained CSA measurements for three peripheral nerves, at specific locations: the median nerve, in the carpal tunnel (MT); the ulnar nerve, at the cubital tunnel site (UT) and at the pre-tunnel site (UPT); and the common fibular nerve, near the fibular head (FH). We calculated the CSA indices between the same sites on different sides (ΔCSAs) and between the ulnar nerve tunnel and pre-tunnel sites on the same side (ΔTPT).

Results

A total of 132 neural sites were analyzed, and the following CSA values (mean ± SD, median) were obtained: MT (6.3 ± 1.9 mm², 6.0 mm²); UT (6.2 ± 1.6 mm², 6.1 mm²); UPT (5.6 ± 1.7 mm², 5.4 mm²); and FH (10.0 ± 3.7 mm², 9.9 mm²). The ΔCSA values (mean ± SD, median) were as follows: MT (0.85 ± 0.7 mm², 0.95); UT (0.81 ± 0.62 mm², 0.95); UPT (0.61 ± 0.51 mm², 0.5); and FH (1.0 ± 0.77 mm², 1.0). The ΔTPT (mean ± SD, median) was (1.0 ± 0.8 mm², 1.0).

Conclusion

Among individuals in Brazil, peripheral nerve CSA values tend to be higher among males and to increase with aging. However, the same does not appear to hold true for the ΔCSA or the ΔTPT, the exception being the difference between the right and left UT. Differences in CSA values greater than 2.5 mm² between sides or between sites along the same nerve can indicate asymmetry or focal thickening in neuropathy, respectively.

Vagus nerve ultrasound in transthyretin familial amyloid polyneuropathy: A pilot study

BACKGROUND AND PURPOSE

Autonomic dysfunction is common in transthyretin familial amyloid polyneuropathy (TTR-FAP). Because ultrasonography is a powerful tool to study peripheral neuropathy, vagus nerve (VN) ultrasonography was used in our study to investigate the possible changes of the dimension of VN in TTR-FAP.

METHODS

Eighteen patients with TTR-FAP and 17 age- and gender-matched individuals without any neuropathies were enrolled in a pilot study. The cross-sectional areas (CSAs) were measured bilaterally on transverse scans of vagus, median, and ulnar nerves. Clinical data were collected to explore the correlations with CSAs of VN.

RESULTS

The median CSAs of VN in TTR-FAP were 3.5 (2.0-6.0) mm² on the right side and 2.5 (1.0-6.0) mm² on the left side, compared with 2.0 (1.0-3.0) mm² and 1.0 (1.0-2.0) mm² for healthy controls (HCs). There was a significant difference between the two groups on both sides (p < .001). The mean VN CSAs were correlated positively with the course of disease (r = .7203, p = .0016)（not including the patient with the longest disease course), the Composite Autonomic Symptom Score 31 (r = .5252, p = .0252), the left ventricular posterior wall thickness (r = .5426, p = .0200), and the interventricular septum thickness (r = .5103, p = .0305). The cutoff values of right and left VN CSAs to identify TTR-FAP from HCs were 2.5 and 1.5 mm² and the areas under the curve were .9395 and .8856, with a high sensitivity (.889 and .889) and specificity (.941 and .765), respectively.

CONCLUSION

VN enlargement is prevalent among TTR-FAP patients. VN ultrasonography may be an important clinical tool for assessing the severity of autonomic dysfunction in TTR-FAP.

Neuromuscular sonography detects changes in muscle echotexture and nerve diameter in ICU patients within 24 h

Purpose

During an ICU stay, changes in muscles and nerves occur that is accessible via neuromuscular sonography.

Methods

17 patients recruited from the neurological and neurosurgical ICU (six women; 66 ± 3 years) and 7 healthy controls (three women, 75 ± 3 years) were included. Muscle sonography (rectus abdominis, biceps, rectus femoris and tibialis anterior muscles) using gray-scale values (GSVs), and nerve ultrasound (peroneal, tibial and sural nerves) analyzing the cross-sectional area (CSA) were performed on days 1 (t1), 3 (t2), 5 (t3), 8 (t4), and 16 (t5) after admission.

Results

Time course analysis revealed that GSVs were significantly higher within the patient group for all of the investigated muscles (rectus abdominis: F = 7.536; p = 0.011; biceps: F = 14.761; p = 0.001; rectus femoris: F = 9.455; p = 0.005; tibialis anterior: F = 7.282; p = 0.012). The higher GSVs were already visible at t1 or, at the latest, at t2 (tibialis anterior muscles). CSA was enlarged in all of the investigated nerves in the patient group (peroneal nerve: F = 7.129; p = 0.014; tibial nerve: F = 28.976, p < 0.001; sural nerve: F = 13.051; p = 0.001). The changes were visible very early (tibial nerve: t1; peroneal nerve: t2). The CSA of the motor nerves showed an association with the ventilation time and days within the ICU (t1 through t4; p < 0.05).

Discussion

We detected very early changes in the muscles and nerves of ICU-patients. Nerve CSA might be a useful parameter to identify patients who are at risk for difficult weaning. Therefore our observations might be severity signs of neuromuscular suffering for the most severe patients.

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.

Assessment of Operator Reliability in Ultrasound of the Median and Ulnar Nerve Using Bland-Altman Analysis

Currently, there is no standardized method to evaluate operator reliability in nerve ultrasound. A short prospective protocol using Bland–Altman analysis was developed to assess the level of agreement between operators with different expertise levels. A control rater without experience in nerve ultrasound, three novices after two months of training, an experienced rater with two years of experience, and a reference rater performed blinded ultrasound examinations of the left median and ulnar nerve in 42 nerve sites in healthy volunteers. The precision of Bland–Altman agreement analysis was tested using the Preiss–Fisher procedure. Intraclass correlation coefficients (ICC), coefficients of variation, and Bland–Altman limits of agreement were calculated. The sample size calculation and Preiss–Fisher procedure showed a sufficient precision of Bland–Altman agreement analysis. Limits of agreement of all trained novices ranged from 2.0 to 2.9 mm² and were within the test’s maximum tolerated difference. Ninety-five percent confidence intervals of limits of agreement revealed a higher precision in the experienced rater’s measurements. Operator reliability in nerve ultrasound of the median and ulnar nerve arm nerves can be evaluated with a short prospective controlled protocol using Bland–Altman statistics, allowing a clear distinction between an untrained rater, trained novices after two months of training, and an experienced rater.

Influence of Demographic Factors on Nerve Ultrasound of Healthy Participants in a Multiethnic Asian Population

Background:

High-resolution nerve ultrasound provides morphological information of peripheral nerves. We aimed to determine the normal ultrasonographic reference values of nerve cross-sectional area (CSA) in multiethnic Malaysian healthy participants.

Methods:

Nerve ultrasound of the median, ulnar, radial, tibial, fibular, and sural nerves was performed in 84 healthy participants at anatomical-defined locations. The CSA at each scanned site was measured by tracing circumferentially inside the hyperechoic rim of each nerve. Comparisons were made between genders and ethnic groups. Correlations with age, ethnicity, gender, height, weight, and body mass index (BMI) were evaluated.

Results:

CSA values and reference ranges in healthy participants were generated. Nerve CSA was significantly different in different gender (P = 0.002–0.032) and ethnic groups (P = 0.006–0.038). Men had larger nerve CSA than women, and Malay participants had larger nerve CSA compared to other ethnic groups. Nerve CSA had significant correlations to age, height, weight, and BMI (r = 0.220–0.349, P = 0.001–0.045).

Conclusion:

This study provides normative values for CSA of peripheral nerves in a multiethnic Malaysian population, which serves as reference values in the evaluation of peripheral nerve disorders. The ethnic differences in nerve CSA values should be considered during nerve ultrasound.

Electrodiagnosis of Common Mononeuropathies: Median, Ulnar, and Fibular (Peroneal) Neuropathies

This article addresses common mononeuropathies seen in the electrodiagnostic laboratory. The most common mononeuropathies-median neuropathy at the wrist (carpal tunnel syndrome), ulnar neuropathy at the elbow, and fibular (peroneal) neuropathy at the fibular head-are reviewed. The causes, clinical presentations, approached to the electrodiagnostic studies (including nerve conduction studies and needle electromyography), and the typical findings are discussed.

Magnetic Resonance Imaging as a Biomarker in Diabetic and HIV-Associated Peripheral Neuropathy: A Systematic Review-Based Narrative

Background: Peripheral neuropathy can be caused by diabetes mellitus and HIV infection, and often leaves patients with treatment-resistant neuropathic pain. To better treat this condition, we need greater understanding of the pathogenesis, as well as objective biomarkers to predict treatment response. Magnetic resonance imaging (MRI) has a firm place as a biomarker for diseases of the central nervous system (CNS), but until recently has had little role for disease of the peripheral nervous system. Objectives: To review the current state-of-the-art of peripheral nerve MRI in diabetic and HIV symmetrical polyneuropathy. We used systematic literature search methods to identify all studies currently published, using this as a basis for a narrative review to discuss major findings in the literature. We also assessed risk of bias, as well as technical aspects of MRI and statistical analysis. Methods: Protocol was pre-registered on NIHR PROSPERO database. MEDLINE, Web of Science and EMBASE databases were searched from 1946 to 15th August 2020 for all studies investigating either diabetic or HIV neuropathy and MRI, focusing exclusively on studies investigating symmetrical polyneuropathy. The NIH quality assessment tool for observational and cross-sectional cohort studies was used for risk of bias assessment. Results: The search resulted in 18 papers eligible for review, 18 for diabetic neuropathy and 0 for HIV neuropathy. Risk of bias assessment demonstrated that studies generally lacked explicit sample size justifications, and some may be underpowered. Whilst most studies made efforts to balance groups for confounding variables (age, gender, BMI, disease duration), there was lack of consistency between studies. Overall, the literature provides convincing evidence that DPN is associated with larger nerve cross sectional area, T2-weighted hyperintense and hypointense lesions, evidence of nerve oedema on Dixon imaging, decreased fractional anisotropy and increased apparent diffusion coefficient compared with controls. Analysis to date is largely restricted to the sciatic nerve or its branches. Conclusions: There is emerging evidence that various structural MR metrics may be useful as biomarkers in diabetic polyneuropathy, and areas for future direction are discussed. Expanding this technique to other forms of peripheral neuropathy, including HIV neuropathy, would be of value. Systematic Review Registration: (identifier: CRD 42020167322) https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=167322.

Value of shear wave elastography combined with the Toronto clinical scoring system in diagnosis of diabetic peripheral neuropathy

To evaluate the diagnostic values of shear wave elastography (SWE) alone and in combination with the Toronto clinical scoring system (TCSS) on diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes mellitus (T2DM).The study included 41 DPN patients, 42 non-DPN patients, and 21 healthy volunteers. Conventional ultrasonography and SWE were performed on the 2 sides of the tibial nerves, and cross-sectional area (CSA) and nerve stiffness were measured. TCSS was applied to all patients. A receiver operating characteristic curve analysis was performed.The stiffness of the tibial nerve, as measured as mean, minimum or maximum elasticity, was significantly higher in patients in the DPN group than the other groups (P < .05). The tibial nerve of subjects in the non-DPN group was significantly stiffer compared to the control group (P < .05). There was no significant difference of the tibial nerve CSA among the 3 groups (P > .05). Mean elasticity of the tibial nerve with a cutoff of 71.3 kPa was the most sensitive (68.3%) and had a higher area under the curve (0.712; 0.602-0.806) among the 3 shear elasticity indices for diagnosing DPN when used alone. When combining SWE with TCSS in diagnosing DPN, the most effective parameter was the EMax, which yielded a sensitivity of 100.00% and a specificity of 95.24%.SWE is a better diagnostic tool for DPN than the conventional ultrasonic parameter CSA, and a higher diagnostic value is attained when combining SWE with TCSS.

Review Article "Spotlight on Ultrasonography in the Diagnosis of Peripheral Nerve Disease: The Evidence to Date"

Neuromuscular ultrasound is rapidly becoming incorporated into clinical practice as a standard tool in the assessment of peripheral nerve diseases. Ultrasound complements clinical phenotyping and electrodiagnostic evaluation, providing critical structural anatomical information to enhance diagnosis and identify structural pathology. This review article examines the evidence supporting neuromuscular ultrasound in the diagnosis of compressive mononeuropathies, traumatic nerve injury, generalised peripheral neuropathy and motor neuron disease. Extending the sonographic evaluation of nerves beyond simple morphological measurements has the potential to improve diagnostics in peripheral neuropathy, as well as advancing the understanding of pathological mechanisms, which in turn will promote precise therapies and improve therapeutic outcomes.

Magnetization Transfer Ratio of Peripheral Nerve and Skeletal Muscle : Correlation with Demographic Variables in Healthy Volunteers

Purpose

To assess the correlation of peripheral nerve and skeletal muscle magnetization transfer ratio (MTR) with demographic variables.

Methods

In this study 59 healthy adults evenly distributed across 6 decades (mean age 50.5 years ±17.1, 29 women) underwent magnetization transfer imaging and high-resolution T2-weighted imaging of the sciatic nerve at 3 T. Mean sciatic nerve MTR as well as MTR of biceps femoris and vastus lateralis muscles were calculated based on manual segmentation on six representative slices. Correlations of MTR with age, body height, body weight, and body mass index (BMI) were expressed by Pearson coefficients. Best predictors for nerve and muscle MTR were determined using a multiple linear regression model with forward variable selection and fivefold cross-validation.

Results

Sciatic nerve MTR showed significant negative correlations with age (r = −0.47, p < 0.001), BMI (r = −0.44, p < 0.001), and body weight (r = −0.36, p = 0.006) but not with body height (p = 0.55). The multiple linear regression model determined age and BMI as best predictors for nerve MTR (R² = 0.40). The MTR values were different between nerve and muscle tissue (p < 0.0001), but similar between muscles. Muscle MTR was associated with BMI (r = −0.46, p < 0.001 and r = −0.40, p = 0.002) and body weight (r = −0.36, p = 0.005 and r = −0.28, p = 0.035). The BMI was selected as best predictor for mean muscle MTR in the multiple linear regression model (R² = 0.26).

Conclusion

Peripheral nerve MTR decreases with higher age and BMI. Studies that assess peripheral nerve MTR should consider age and BMI effects. Skeletal muscle MTR is primarily associated with BMI but overall less dependent on demographic variables.

Supplementary Information

The online version of this article (10.1007/s00062-021-01067-5) contains supplementary material, which is available to authorized users.