Quantitative assessment of nerve echogenicity: comparison of methods for evaluating nerve echogenicity in ulnar neuropathy at the elbow

Clinical Application of Ultrasound-guided Electrode Placement and Detection of Nerve Action Potential

BACKGROUND

 We explore a minimally invasive method (combined ultrasound detection, electrode placement and electrophysiologic nerve examination) to evaluate the early-stage quality of a nerve suture site.

METHODS

 Ten patients with median and/or ulnar nerve injuries who had undergone nerve suture were recruited. Postoperative ultrasound examination found that the nerve injury was sutured. Then, a stimulating electrode and recording electrode were located beside the nerve proximal and distal to the suture site guided by ultrasound. Measurement of nerve action potentials (NAP) were performed with these electrodes, followed by surgical exploration. The pre- and intraoperative electrophysiologic findings were compared, together with amplitude, latency, and wave shape of NAP.

RESULTS

 Of the 10 patients, 3 patients were diagnosed with median nerve injury, 2 with ulnar nerve injury, and 5 with the median nerve and ulnar nerve injury. NAP could not be detected pre- and intraoperatively in three median nerves from three patients and in two ulnar nerves from two patients. NAP was detected in 10 nerves from the remaining 5 patients. The pre- and intraoperative NAP results showed consistent results concerning the status of the nerve suture. Wilcoxon's signed-rank test indicated no significant difference in the amplitude and latency detected via sonographically placed electrodes and during surgical exploration. The number of negative-phase waves were equally distributed.

CONCLUSION

 Ultrasound-guided electrode placement and NAP detection can substitute surgery and serve as a minimally invasive approach to evaluate the regeneration of a sutured nerve.

Qualitative and quantitative comparison of two semi-manual retinal vascular density analyzing methods on optical coherence tomography angiography images of healthy individuals

The aim of this study was to evaluate qualitative and quantitative differences in vascular density analysis of an established and a novel alternative for post-processing on optical coherence tomography angiography (OCTA) images in healthy individuals. OCTA examinations of 38 subjects were performed. After extracting the images, two semi-manual post-processing techniques, the already established Mexican hat filtering (MHF) and an alternative, the Shanbhag thresholding (ST) were applied. We assessed Vessel Density (VD), Skeleton Density (SkD) and Vessel Diameter Index (VDI). We analyzed the results in order to establish similarities or potentially relevant differences. Regarding SkD and VD, MHF generally gave higher values than ST. Simultaneously, mean values were also predominantly higher by MHF; however, standard deviations (SD) were higher by ST (range [mean ± SD]: 0.054 ± 0.038 to 0.134 ± 0.01 and 0.134 ± 0.095 to 0.362 ± 0.028 vs 0.012 ± 0.014 to 0.087 ± 0.03 and 0.039 ± 0.047 to 0.4 ± 0.095 for SkD and VD with MHF vs SkD and VD with ST, respectively). Values of VDI were considerably higher with ST than with MHF, while standard deviation was still significantly higher with ST (range [mean ± SD]: 2.459 ± 0.144 to 2.71 ± 0.084 and 2.983 ± 0.929 to 5.19 ± 1.064 for VDI with MHF and ST, respectively). The noise level reduction of the two methods were almost identical (noise levels: 65.8% with MHT and 65.24% with ST). Using MHF, the vascular network gets more fragmented by an average of 40% compared to ST. Both methods allow the segmentation of the vascular network and the examination of vascular density parameters, but they produce largely inconsistent results. To determine if these inconsistent results are clinically meaningful, and which method is more suitable for clinical use, our results provide further evidence that detailed understanding of the image analysis method is essential for reliable decision making for patients with retinal pathology. For longitudinal monitoring, use of the same image processing method is recommended.

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).

Image analysis can reliably quantify median nerve echogenicity and texture changes in patients with carpal tunnel syndrome

OBJECTIVE

To study the ability of image analysis measures to quantify echotexture changes of median nerve in order to provide a complementary diagnostic tool in CTS.

METHODS

Image analysis measures (gray level co-occurrence matrix (GLCM), brightness, hypoechoic area percentage using max entropy and mean threshold) were calculated in normalized images of 39 (19 younger and 20 older than 65y) healthy controls and 95 CTS patients (37 younger and 58 older than 65y).

RESULTS

Image analysis measures were equivalent or superior (older patients) to subjective visual analysis. In younger patients, GLCM measures showed equivalent diagnostic accuracy with cross sectional area (CSA) (Area Under Curve (AUC for inverse different moment = 0.97). In older patients all image analysis measures showed similar diagnostic accuracy to CSA (AUC for brightness = 0.88). Moreover, they had abnormal values in many older patients with normal CSA values.

CONCLUSIONS

Image analysis reliably quantifies median nerve echotexture alterations in CTS and offers similar diagnostic accuracy to CSA measurement.

SIGNIFICANCE

Image analysis may offer added value to existing measures in the evaluation of CTS, especially in older patients. Its clinical implementation would require incorporation of mathematically simple software code for online nerve image analysis in ultrasound machines.

Quantitative Ultrasound Techniques Used for Peripheral Nerve Assessment

AIM

This review article describes quantitative ultrasound (QUS) techniques and summarizes their strengths and limitations when applied to peripheral nerves.

METHODS

A systematic review was conducted on publications after 1990 in Google Scholar, Scopus, and PubMed databases. The search terms "peripheral nerve", "quantitative ultrasound", and "elastography ultrasound" were used to identify studies related to this investigation.

RESULTS

Based on this literature review, QUS investigations performed on peripheral nerves can be categorized into three main groups: (1) B-mode echogenicity measurements, which are affected by a variety of post-processing algorithms applied during image formation and in subsequent B-mode images; (2) ultrasound (US) elastography, which examines tissue stiffness or elasticity through modalities such as strain ultrasonography or shear wave elastography (SWE). With strain ultrasonography, induced tissue strain, caused by internal or external compression stimuli that distort the tissue, is measured by tracking detectable speckles in the B-mode images. In SWE, the propagation speed of shear waves, generated by externally applied mechanical vibrations or internal US "push pulse" stimuli, is measured to estimate tissue elasticity; (3) the characterization of raw backscattered ultrasound radiofrequency (RF) signals, which provide fundamental ultrasonic tissue parameters, such as the acoustic attenuation and backscattered coefficients, that reflect tissue composition and microstructural properties.

CONCLUSIONS

QUS techniques allow the objective evaluation of peripheral nerves and reduce operator- or system-associated biases that can influence qualitative B-mode imaging. The application of QUS techniques to peripheral nerves, including their strengths and limitations, were described and discussed in this review to enhance clinical translation.

Nerve Echogenicity: Changes in High-Resolution Nerve Ultrasound in Carpal Tunnel Syndrome after Surgery

The aim of our prospective study was to detect changes in nerve echogenicity of the median nerve before and after successful surgery in patients with carpal tunnel syndrome (CTS) using high-resolution ultrasound. Fifteen patients with a definite diagnosis of CTS who underwent surgery were scanned by one examiner with high-resolution ultrasound, and images were analyzed by two blinded raters using ImageJ to assess the echogenicity of the median nerve (fraction of black) with a semiautomated thresholding technique before and 3 mo after surgery compared with 15 controls. In CTS patients, nerve echogenicity before surgery was significantly lower compared with that of controls (fraction of black: mean 63.9 vs. 44.6, p < 0.0001). Three months after surgery nerve echogenicity significantly increased (fraction of black was lower, mean 55.5; p < 0.0001) as a possible sign of reduction of intraneural edema, but did not reach the values of healthy controls. Semi-automated evaluation of the echogenicity of the median nerve may be used as a marker of successful carpal tunnel release. Further studies are warranted to detect how nerve echogenicity changes after unsuccessful carpal tunnel release.

Effects of a preoperative neuromobilization program offered to individuals with carpal tunnel syndrome awaiting carpal tunnel decompression surgery: A pilot randomized controlled study

STUDY DESIGN

Pilot randomized controlled trial with parallel groups.

INTRODUCTION

Engaging individuals with carpal tunnel syndrome (CTS) awaiting carpal tunnel decompression surgery in a preoperative rehabilitation program may mitigate pain and sensorimotor impairments, enhance functional abilities before surgery, and improve postoperative outcomes.

PURPOSE OF THE STUDY

To assess the feasibility and the efficacy of a novel preoperative neuromobilization exercise program (NEP).

METHODS

Thirty individuals with CTS were randomly allocated into a four-week home-based neuromobilization exercise group or a standard care group while awaiting surgery. Outcome measures included feasibility (ie, recruitment, attrition, adherence, satisfaction, and safety) and efficacy metrics (ie, median nerve integrity and neurodynamics, tip pinch grip, pain, and upper limb functional abilities) collected before (ie, at the baseline and about four weeks later) and four weeks after surgery.

RESULTS

Thirty individuals with CTS were recruited (recruitment rate = 11.8%) and 25 completed the study (attrition rate = 16.7%). Adherence (94%) and satisfaction with the program (eg, enjoy the exercises and likeliness to repeat the NEP (≥4.2/5) were high and no serious adverse event was reported. NEP-related immediate pre- and post-surgery beneficial effects on pain interference were documented (P = .05, η² = .10), whereas an overall increased neurodynamics (P = .04, η² = .11) and decreased pain severity (P = .01, η² = .21) were observed.

DISCUSSION

Engaging in the proposed NEP has limited beneficial effect as a stand-alone intervention on pre- and post-surgery outcomes for individuals with CTS. Expanding the program's content and attribute by adding other components including desensitization maneuvers and novel therapies promoting corticospinal plasticity is recommended.

CONCLUSION

A preoperative NEP completed by individuals with CTS awaiting surgery is feasible, acceptable, and safe. However, given the limited beneficial effectsof the program, revision of its content and attributes is recommended before proceeding to large-scale trials.

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.

Quantitative assessment of muscle echogenicity in Charcot-Marie-Tooth disease type 1A by automatic thresholding methods

OBJECTIVE

To investigate the utility of automatic thresholding methods for quantitative muscle echogenicity assessment as a marker of disease severity in Charcot-Marie-Tooth disease type 1A (CMT1A).

METHODS

Muscle ultrasound was performed in 15 CMT1A patients and 7 healthy controls. Muscle echogenicity of six limb muscles in each subject was assessed by 16 automatic thresholding methods and conventional grey-scale analysis. Echogenicity of each method in CMT1A patients was compared with that in controls. A correlation between the echogenicity and CMT neuropathy score (CMTNS) was also analysed in CMT1A patients.

RESULTS

Significant differences in mean echogenicity of the 6 muscles between CMT1A patients and controls were found both in grey-scale analysis (p < 0.01) and 11 of the 16 automatic thresholding methods (p < 0.05 in each method). In CMT1A patients, mean echogenicity of the 6 muscles was positively correlated with CMTNS in 8 of the 16 automatic thresholding methods, but not in grey-scale analysis.

CONCLUSION

Automatic thresholding methods can be used to detect the difference in muscle echogenicity between CMT1A patients and controls. Echogenicity parameters correlate with the disease severity.

SIGNIFICANCE

Quantitative muscle echogenicity assessment by automatic thresholding methods shows potential as a surrogate marker of disease progression in CMT1A.

Quantitative assessment of intraneural vascular alterations in peripheral nerve trauma using high-resolution neurosonography: technical note

High-resolution neurosonography (HRNS) has become a major imaging modality in assessment of peripheral nerve trauma in the recent years. However, the vascular changes of traumatic lesions have not been quantitatively assessed in HRNS. Here, we describe the vascular-ratio, a novel HRNS-based quantitative parameter for the assessment of intraneural vascular alterations in patients with nerve lesions. N = 9 patients suffering from peripheral nerve trauma were examined clinically, electrophysiologically and with HRNS (SonoSite Exporte, Fuji). Image analyses using Fiji included determination of the established fascicular ratio (FR), the cross-section ratio (CSR), and as an extension, the calculation of a vascular ratio (VR) of the healthy versus damaged nerve and a muscle perfusion ratio (MPR) in comparison to a healthy control group. The mean VR in the healthy part of the affected nerve (14.14%) differed significantly (p < 0.0001) from the damaged part (VR of 43.26%). This coincides with significant differences in the FR and CSR calculated for the damaged part versus the healthy part and the controls. In comparison, there was no difference between VRs determined for the healthy part of the affected nerve and the healthy controls (14.14% / 17.72%). However, the MPR of denervated muscles was significantly decreased compared to the non-affected contralateral controls. VR and MPR serve as additional tools in assessing peripheral nerve trauma. Image analysis and calculation are feasible. Combined with the more morphologic FR and CSR, the VR and MPR provide a more detailed insight into alterations accompanying nerve trauma.

Expert consensus on the combined investigation of ulnar neuropathy at the elbow using electrodiagnostic tests and nerve ultrasound

The addition of ultrasound (US) to electrodiagnostic (EDX) tests can significantly enhance the accuracy of testing for ulnar neuropathy at the elbow (UNE). We aimed to obtain expert consensus to guide clinicians on the combined use of EDX and US in UNE investigation. Consensus was achieved using the Delphi method. Two consecutive anonymised questionnaires were submitted to 15 experts, who were asked to choose their level of agreement with each statement. Consensus was pre-defined as ≥ 80% rating agreement. The experts concluded that all investigations of UNE should include both nerve conduction studies and US. There was consensus that US should include cross-sectional area measurement and assessment of nerve mobility at the elbow, and that the entire ulnar nerve should be imaged. This study defined expert opinion on the 'core' techniques that should be used routinely in the UNE investigation using EDX and US. Areas with lack of consensus highlighted some controversial issues in the current use of these diagnostic modalities and the need for future research. This document is an initial step to guide clinicians on the combined investigation of UNE using EDX and US, to be regularly updated as new research emerges.

Accurate automated diagnosis of carpal tunnel syndrome using radiomics features with ultrasound images: A comparison with radiologists' assessment

PURPOSE

Ultrasonography is the most common imaging modality used to diagnose carpal tunnel syndrome (CTS). Recently artificial intelligence algorithms have been used to diagnose musculoskeletal diseases accurately without human errors using medical images. In this work, a computer-aided diagnosis (CAD) system is developed using radiomics features extracted from median nerves (MN) to diagnose CTS accurately.

METHOD

This study is performed on 228 wrists from 65 patients and 57 controls, with an equal number of control and CTS wrists. Nerve conduction study (NCS) is considered as the gold standard in this study. Two radiologists used two guides to evaluate and categorize the pattern and echogenicity of MNs. Radiomics features are extracted from B-mode ultrasound images (Ultrasomics), and the robust features are fed into support vector machine classifier for automated classification. The diagnostic performances of two radiologists and the CAD system are evaluated using ROC analysis.

RESULTS

The agreement of two radiologists was excellent for both guide 1 and 2. The honey-comb pattern clearly appeared in control wrists (based on guide 1). In addition, CTS wrists indicated significantly lower number of fascicles in MNs (based on guide 2). The area under ROC curve (AUC) of the radiologist 1 and 2 are 0.658 and 0.667 based on guide 1 and 0.736 and 0.721 based on guide 2, respectively. The CAD system indicated higher performance than two radiologists with AUC of 0.926.

CONCLUSION

The proposed CAD system shows the benefit of using ultrasomics features and can assist radiologists to diagnose CTS accurately.

Novel multimodal molecular imaging of Vitamin H (Biotin) transporter activity in the murine placenta

Vitamin H (biotin) is delivered to the fetus transplacentally by an active biotin-transport mechanism and is critical for fetal development. Our objective was to develop a comprehensive MRI technique for mapping biotin transporter activity in the murine placenta. Visualization of transporter activity can employ MRI's unique T₂*-dependent signal 'off-switch', which is triggered by transporter mediated aggregation of biotinylated contrast agent (b-BSA-Gd-DTPA). MRI data were collected from pregnant mice after administration of b-BSA-Gd-DTPA and analyzed using a new sub-voxel biophysical signal model. Validation experiments included competition with native biotin, comparative tests using PET, histology, and ICPMS. MRI signal was governed by binding, aggregation, and clearance of biotin (confirmed by histology). Signal dynamics reflected the placenta's perfusion pattern modulated by biotin transporter activity and trophoblast mediated retention, and were in congruence with a three-compartment sub-voxel model. Pre-saturation of the transporters with free biotin suppressed b-BSA-Gd-DTPA uptake. The results were confirmed by PET, histology and ICPMS. The presented MRI-based platform allows to track activity of essential molecular transporters in the placenta, reflecting a transporter-mediated uptake, followed by retention and aggregation, and recycling associated with the large b-BSA-Gd-DTPA conjugate. The presented DCE-MRI technique can furthermore be used to map and characterize microstructural compartmentation and transporter activity without exposing the fetus to contrast media.

Charcot-Marie-Tooth disease type 1A: Longitudinal change in nerve ultrasound parameters

BACKGROUND

This study aimed to elucidate the longitudinal changes in nerve ultrasound parameters of adult Charcot-Marie-Tooth disease type 1A (CMT1A) patients.

METHODS

Fifteen adult patients with CMT1A prospectively underwent nerve ultrasound and clinical assessment (CMT neuropathy score [CMTNS]) at baseline and 5 y later. Nerve cross-sectional area (CSA) and echogenicity were measured in the median and sural nerves. Changes in ultrasound parameters and CMTNS and correlation between changes of ultrasound parameters and CMTNS were analyzed.

RESULTS

Median and sural nerve CSAs did not change over 5 y, although CMTNS increased (P < .01). Nerve echogenicity in the sural nerve decreased over 5 y (P = .045). No correlations between changes in nerve ultrasound parameters and CMTNS were identified.

CONCLUSIONS

No longitudinal changes in nerve size was detected in adult CMT1A. Exploring the factors that determine nerve size in childhood CMT1A may lead to the development of treatments.

Optimal Choice of Ultrasound-Based Measurements for the Diagnosis of Ulnar Neuropathy at the Elbow: A Meta-Analysis of 1961 Examinations

OBJECTIVE. The purpose of this study was to determine the optimal ultrasound (US) measurement technique and cutoff value for the diagnosis of ulnar neuropathy at the elbow. MATERIALS AND METHODS. A systematic literature search was conducted of the PubMed, Embase, Scopus, and Web of Science databases for studies evaluating the diagnostic accuracy of US of patients with ulnar neuropathy at the elbow before April 2019. Random-effects modeling was performed to compare the sensitivity, specificity, and diagnostic odds ratio (DOR) of different US measurements, including diameter and cross-sectional area (CSA) of the nerve at the medial epicondyle or proximal and distal levels, maximal diameter, maximal CSA, and nerve ratios. Sensitivity and metaregression analyses were performed to assess the impact of clinical and imaging-based variables on the DOR of US. RESULTS. Among 820 retrieved studies, 19 studies (1961 examinations) were included. Measuring the CSA of the ulnar nerve at the medial epicondyle with a cutoff value greater than 10-10.5 mm² had higher sensitivity (80.4%, 95% CI, 75.4-84.7%) than other techniques. Nerve ratios had higher specificity (89.1%, 95% CI, 85.8-91.8%) than other measurements; however, the definition of ratios and cutoff values varied across studies. ROC analysis showed higher diagnostic performance for measuring CSA at the medial epicondyle (AUC, 0.931). The mean CSA value was a significant predictor of the DOR of US (β coefficient, 0.307 ± 0.074; p < 0.001). Every 1-mm² larger CSA was associated with a 36% increase in DOR. The diagnostic performance of US was the same in any degree of elbow flexion. CONCLUSION. Measuring CSA of the ulnar nerve at the medial epicondyle has sensitivity and diagnostic performance superior to those of other techniques for the diagnosis of ulnar neuropathy at the elbow.

Current and future applications of ultrasound imaging in peripheral nerve disorders

Neuromuscular ultrasound (NMUS) is a rapidly evolving technique used in neuromuscular medicine to provide complimentary information to standard electrodiagnostic studies. NMUS provides a dynamic, real time assessment of anatomy which can alter both diagnostic and management pathways in peripheral nerve disorders. This review describes the current and future techniques used in NMUS and details the applications and developments in the diagnosis and monitoring of compressive, hereditary, immune-mediated and axonal peripheral nerve disorders, and motor neuron diseases. Technological advances have allowed the increased utilisation of ultrasound for management of peripheral nerve disorders; however, several practical considerations need to be taken into account to facilitate the widespread uptake of this technique.

High-Resolution Nerve Ultrasound to Assess Nerve Echogenicity, Fascicular Count, and Cross-Sectional Area Using Semiautomated Analysis

BACKGROUND AND PURPOSE

Little is known about echogenicity and fascicular structure observed in high-resolution nerve ultrasound (HRUS) in both healthy subjects and patients with peripheral nerve disease. The aim of this study was to evaluate the reliability of echogenicity, fascicle count, and fascicle size analysis, to create standard values and compare these parameters to patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

Median, ulnar, radial, tibial, and fibular nerve of 79 healthy subjects and patients were scanned by one examiner using HRUS. Image analysis regarding echogenicity, fascicle count, and fascicle cross-sectional area (CSA) was performed by two independent raters semiautomatically using ImageJ. Pearson correlation coefficient r reflected interrater reliability (IR), and intraclass correlation coefficient (ICC) determined intrarater reliability (IAR). Results of healthy subjects were compared to 20 patients with CIDP by analysis of variance.

RESULTS

IR was very good for echogenicity (r = .9) and good for fascicle count and size of the largest fascicle (r = .64/.56). IAR was very good for all three parameters (ICC = .9/.83/.74). Healthy subjects had a wide range of values. CIDP patients were in range of healthy subjects. Clinically progressive CIDP patients (defined as an increase in Overall Disability Sum Score by ≥1 point) had a lower fraction of black than healthy controls and stable CIDP patients (P < .001).

CONCLUSION

Semiautomated evaluation of echogenicity, fascicle count, and fascicle CSA is reliable. Cutoff values to differentiate between healthy persons and CIDP do not exist. Echogenicity is useful for detecting clinically progressive CIDP patients and should be used in clinical context or intraindividual course.

Fascicular Ratio Pilot Study: High-Resolution Neurosonography-A Possible Tool for Quantitative Assessment of Traumatic Peripheral Nerve Lesions Before and After Nerve Surgery

BACKGROUND

Clinical and electrophysiological assessments prevail in evaluation of traumatic nerve lesions and their regeneration following nerve surgery in humans. Recently, high-resolution neurosonography (HRNS) and magnetic resonance neurography have gained significant importance in peripheral nerve imaging. The use of the grey-scale-based "fascicular ratio" (FR) was established using both modalities allowing for quantitative assessment.

OBJECTIVE

To find out whether FR using HRNS can assess nerve trauma and structural reorganization in correlation to postoperative clinical development.

METHODS

Retrospectively, 16 patients with operated traumatic peripheral nerve lesions were included. The control group consisted of 6 healthy volunteers. All imaging was performed with a 15 to 6 MHz ultrasound probe (SonoSite X-Porte; Fujifilm, Tokyo, Japan). FR was calculated using Fiji () on 8-bit-images ("MaxEntropy" using "Auto-Threshold" plug-in).

RESULTS

Thirteen of 16 patients required autologous nerve grafting and 3 of 16 extra-intraneural neurolysis. There was no statistical difference between the FR of nonaffected patients' nerve portion with 43.48% and controls with FR 48.12%. The neuromatous nerve portion in grafted patients differed significantly with 85.05%. Postoperatively, FR values returned to normal with a mean of 39.33%. In the neurolyzed patients, FR in the affected portion was 78.54%. After neurolysis, FR returned to healthy values (50.79%). Ten of 16 patients showed clinical reinnervation.

CONCLUSION

To our best knowledge, this is the first description of FR using HRNS for quantitative assessment of nerve damage and postoperative structural reorganization. Our results show a significant difference in healthy vs lesioned nerves and a change in recovering nerve portions towards a more "physiological" ratio. Further evaluation in larger patient groups is required.

Ultrasound Measurements and Assessments of the Ulnar Nerve at the Elbow and Cubital Tunnel: A Scoping Review

Ulnar neuropathy at the elbow (UNE) is the second most frequent peripheral nerve entrapment neuropathy in the upper extremity. The diagnosis is determined through a combination of history, physical examination, and electrodiagnostic testing. However, the use of high-resolution sonography is increasing, with sonographic measurements of ulnar nerve dimension established as a reliable diagnostic criterion for UNE. Sonographic imaging can describe anatomical features beyond ulnar nerve size, and therefore additional observations could potentially be used in UNE diagnosis and treatment follow-up. This review was a scoping of the literature on different sonographic measurements and assessments that have been reported to evaluate the ulnar nerve and cubital tunnel. This should provide a guide to scanning protocols for sonographers.

Neuromuscular morphometric characteristics in low back pain with unilateral radiculopathy caused by disc herniation: An ultrasound imaging evaluation

BACKGROUND

Little is known about the neuromuscular morphometric characteristics in patients with sciatica.

OBJECTIVE

To evaluate the possible changes of nerve and muscle structures in patients with low back pain with unilateral radiculopathy due to lumbar disc herniation by ultrasound imaging.

DESIGN

A case-control observational study.

METHODS

Forty individuals were divided into case (n = 20; low back pain with unilateral radiculopathy due to disc herniation), and healthy control groups (n = 20). The thickness of lumbar multifidus at L5 level, and of lower limb muscles (i.e., biceps femoris, medial gastrocnemius, and soleus) was measured during both rest and full contraction to calculate the rest/contraction ratio of these muscles. Additionally, the sciatic nerve cross-sectional area and the echogenicity of the nerve and muscles were measured based on ultrasound imaging. The association between severity of low back pain radiculopathy (i.e., pain and patients' perceived disability) and rest/contraction ratio was assessed.

RESULTS

Patients with sciatica showed sciatic nerve enlargement, and different contraction ratios for multifidus (at L5)/ankle plantar flexors compared to the controls. The rest/contraction ratio for biceps femoris was similar between the two groups.

CONCLUSION

According to these findings, ultrasound imaging can be considered a useful tool to detect changes in the sciatic nerve and muscles due to disc herniation. Furthermore, regarding the observation of significant changes in muscle rest/contraction ratio in the multifidus and gastrosoleus, one might attribute these changes to the nerve root compression.

Nerve echogenicity and intranerve CSA variability in high-resolution nerve ultrasound (HRUS) in chronic inflammatory demyelinating polyneuropathy (CIDP)

OBJECTIVE

HRUS is increasingly being used in the diagnosis and evaluation of autoimmune neuropathies such as CIDP. Recently, studies focused not only on changes of nerves size, but also the fascicular structure and the echogenicity changes in CIDP. However, little is known about the alterations of echogenicity in the long-term course in CIDP. The aim of this study was to evaluate echogenicity in CIDP patients in a long-term follow-up period and to analyze the benefit of the evaluation of echogenicity compared to nerve size.

METHODS

20 patients fulfilling the definite diagnostic criteria of CIDP received clinical examination, nerve conduction studies and HRUS every 6 months over a median follow-up time of 34 months. Patients were divided into clinically stable/regressive disease course or progressive disease course according to the development of the inflammatory neuropathy cause and treatment overall disability sum score. Echogenicity of peripheral nerves was measured semi-automated and quantitative. Echogenicity was divided into three classes by fraction of black: hypoechogenic, mixed hypo-/hyperechogenic, hyperechogenic.

RESULTS

Patients with hyperechogenic arm nerves more frequently show clinical worsening, whereas patients with hypoechogenic arm nerves remain stable or even improved over time. In the long-term course of the disease, echogenicity mostly did not change, and if changes occured echogenicity did not correspond to ODSS changes.

CONCLUSION

Echogenicity of the arm nerves in CIDP may be used as a prognostic marker, but not as a follow-up tool for evaluating clinical changes. Further studies in a larger cohort are needed to confirm these results.

Test-retest reliability of nerve and muscle morphometric characteristics utilizing ultrasound imaging in individuals with unilateral sciatica and controls

Background

Ultrasound imaging has been suggested for studying the structure and function of nerves and muscles; however, reliability studies are limited to support the usage. The main aim of this study was to explore the intrarater within-session reliability of evaluating the sciatic nerve and some related muscles morphology by ultrasound imaging.

Methods

Three B-mode images from two scans (transverse and longitudinal) were acquired from the multifidus, biceps femoris, soleus and medial gastrocnemius muscles bilaterally from 15 participants with sciatica and 15 controls in one session, 1-h apart. The data were collected from March to July 2017. Contraction ratio was measured only by longitudinal scan, while the echo intensity was measured using maximum rectangular region of interest in two scans (transverse and longitudinal) for all muscles. Cross-sectional area, direct (tracing) and indirect (ellipsoid formula) methods were used to measure the sciatic nerve. Intraclass correlation coefficient (ICC 3,1), standard error of measurement and minimal detectable change were calculated.

Results

Good to high ICCs (0.80–0.96) were found for muscle contraction ratio in the longitudinal scans in all the muscles in both sciatica and control groups. For echo intensity measurements ICCs ranged from moderate to high, with higher ICCs seen with the maximum region of interest in the transverse scans. The minimal detectable change values ranged between 0.11 and 0.53 cm for contraction ratio.

Conclusions

Ultrasound imaging has high intrarater within-session reliability for assessing the sciatic nerve Cross-sectional area and muscle contraction ratios. Transverse scans with the maximum region of interest result in higher reliability. The sciatic Cross-sectional area is most accurately measured utilizing the direct tracing method rather than the indirect ellipsoid method.

QUANTITATIVE ASSESSMENT OF GINGIVAL INFLAMMATION USING HIGH-RESOLUTION ULTRASOUNDEX-VIVO

This study investigates the feasibility of using high-resolution ultrasound imaging echogenicity to quantitatively diagnose gingival inflammation. Gingival samples were extracted from the study participants during gingivectomy procedures. Ultrasound mechanical scanning of the samples was immediately conducted ex-vivo to render cross-sectional images of high resolution, at different locations. Samples’ histological preparation and analysis was followed after performing ultrasound imaging. Histological sections were then matched with ultrasound images at different sections for each gingival sample. The matched image pairs were used to estimate two quantitative measures; relative inflammation area and ultrasound image echogenicity. These parameters were employed to judge the diagnostic potential of gingival ultrasound imaging. The results show that ultrasound images exhibited low intensity levels at the inflamed gingival regions, while healthy layers showed higher intensity levels. The relative area parameter implied a strong relationship between ultrasound and histological images. Ultrasound echogenicity was found to be statistically significant in differentiating between some inflammation degrees in the studied gingival samples. In summary, ultrasound imaging has the potential to be a noninvasive adjunct diagnostic tool for gingival inflammation, and may help assess the stage of the disease and ultimately limit periodontal disease occurrence; taking into consideration the limits of this study.

Ultrasound assessment of the sural nerve in patients with neuropathic pain after ankle surgery

INTRODUCTION

The sural nerve may be damaged after ankle injury. The aim of our study was to determine the diagnostic utility of high-resolution sonography in patients with ankle fractures treated by open reduction and internal fixation in whom there was a clinical suspicion of sural neuropathy.

METHODS

We examined the ultrasound (US) characteristics of patients with and without postsurgical sural neuropathic pain and healthy volunteers. Cross-sectional area (CSA), echogenicity, and vascularization of the sural nerves were recorded.

RESULTS

Fourteen participants and all sural nerves were identified. CSA (P < 0.001) and vascularization (P = 0.002) were increased in symptomatic patients when compared with asymptomatic patients and healthy volunteers. There were no significant differences in nerve echogenicity (P = 0.983).

DISCUSSION

US may be a valuable tool for evaluating clinically suspected sural nerve damage after ankle stabilization surgery. Sural nerve abnormalities are seen in patients with postsurgical neuropathic pain. Muscle Nerve 57: 407-413, 2018.

Diagnostic value of sonography in treatment-naive chronic inflammatory neuropathies

OBJECTIVE

To determine the diagnostic value of high-resolution ultrasound (HRUS) for detection of chronic inflammatory demyelinating polyneuropathy (CIDP), Lewis-Sumner syndrome (LSS), and multifocal motor neuropathy (MMN).

METHODS

Between January 2013 and January 2015, we enrolled 75 consecutive treatment-naive patients with chronic inflammatory neuropathies and 70 disease controls. We performed extensive nerve conduction and standardized HRUS studies bilaterally of large arm and leg nerves and brachial plexus. We determined optimal sonographic cutoff values of nerve size and used receiver operating characteristic analysis and logistic regression models to identify nerve combinations with optimal diagnostic performance.

RESULTS

Enlargement of median nerve at forearm >10 mm², upper arm >13 mm², and any trunk of brachial plexus >8 mm² was 99% specific for chronic inflammatory neuropathies. A shortened HRUS protocol for detecting this abnormal nerve enlargement showed high sensitivity (83%-95%), positive predictive value (100%), and negative predictive value (98%) in discriminating CIDP, LSS, and MMN from clinical mimics.

CONCLUSIONS

Sonographic enlargement of proximal median nerve segments in the arms and brachial plexus is a key feature of chronic inflammatory neuropathies, which helps to reliably distinguish them from axonal neuropathies and amyotrophic lateral sclerosis.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that, in absence of clinical features that suggest a hereditary demyelinating neuropathy, sonographic enlargement of proximal median nerve segments and brachial plexus accurately identifies patients with chronic inflammatory neuropathies.

Physiological factors influencing median nerve mobility in normal subjects

INTRODUCTION

The purpose of this study was to assess the mobility of the median nerve in the axial plane in normal healthy subjects and to evaluate physiological factors associated with lesser degrees of mobility.

METHODS

Our study included 80 healthy volunteers between 20 and 60 years of age. For all subjects, mobility of the median nerve was assessed with ultrasound at the carpal tunnel.

RESULTS

With wrist and finger flexion, the median nerve moved in all 160 wrists; in 78, the nerve dove deep to the flexor tendons (full), and in 82 it made a partial turn, but did drop below the tendons (partial). Among all demographic factors and sonographic measurements, only height was significantly related to partial mobility.

CONCLUSIONS

Full or partial mobility of the median nerve with wrist flexion is an attribute of normal subjects; partial mobility is common, particularly in taller individuals. Muscle Nerve 54: 883-886, 2016.

Peripheral nerve imaging: Not only cross-sectional area

Peripheral nerve imaging is recognized as a complement to clinical and neurophysiological assessment in the evaluation of peripheral nerves with the ability to impact patient management, even for small and difficult nerves. The European Society of Musculoskeletal Radiology, suggest to use ultrasound (US) for nerve evaluation due to the fact that, in sever anatomical area, magnetic resonance imaging is not able to give additional informations. US could be considered the first-choice approach for the assessment of peripheral nerves. The relative drawback of peripheral nerve US is the long learning curve and the deep anatomic competence to evaluate even small nerves. In the recent years, the role of US in peripheral nerve evaluation has been widened. In the past, nerve US was mainly used to assess nerve-cross sectional area, but now more advanced measurements and considerations are desirable and can boost the role of peripheral nerve US. Nerve echotexture evaluation was defined in 2010: The ratio between the hypoechoic and hyperechoic areas of peripheral nerves on US was called “nerve density”. For evaluation of patients who have peripheral neuropathies, the role of peripheral nerve is US wider than simple cross-sectional area evaluation. Quantitative measurements describing the internal fascicular echotexture of peripheral nerves introduce the concept of considering US as a possible quantitative imaging biomarker technique. The potential of nerve US has started to be uncovered. It seems clear that only cross-sectional area measurement is no more sufficient for a comprehensive US evaluation of peripheral nerves.

Nerve sonography to detect peripheral nerve involvement in vasculitis syndromes

Background

We sought to determine the usefulness of sonography in the detection of nerve involvement in patients with vasculitic neuropathy.

Methods

We enrolled 16 consecutive patients with vasculitic neuropathy (11 systemic vasculitis and 5 single organ peripheral nerve vasculitis), who met the diagnostic criteria of the Peripheral Nerve Society, and 16 disease controls with noninflammatory axonal polyneuropathy (10 cryptogenic, 4 metabolic, 2 hereditary). Patients underwent standardized nerve conduction studies and assessment of muscle strength (Medical Research Council scale), in addition to sonography of large arm and leg nerves, and brachial plexus. Nerves were evaluated bilaterally at predetermined sites for nerve size (cross-sectional area) and presence of hypervascularization.

Results

We found enlarged nerves at common sites of nerve compression in all vasculitic and control patients. Multifocal enlargement in arm nerves, proximal to common sites of nerve compression, was sensitive (94%) and specific (88%) for vasculitic neuropathy. Sonography showed nerve enlargement in 51% of clinically or electrodiagnostically unaffected nerves. Sonography of the brachial plexus was normal. We found hypervascularization in 3 patients with systemic vasculitis.

Conclusions

Sonographic enlargement of arm nerves proximal to sites of nerve compression with sparing of the brachial plexus may indicate a pattern characteristic of patients with vasculitic neuropathy. Sonography may represent a sensitive and specific technique for the detection of inflammatory neuropathy.

Classification of evidence

This study provides Class III evidence that sonographic enlargement of arm nerves proximal to sites of nerve compression accurately identifies patients with vasculitic neuropathy.

Peripheral nerve imaging

Disorders of peripheral nerve have been traditionally diagnosed and monitored using clinical and electrodiagnostic approaches. The last two decades have seen rapid development of both magnetic resonance imaging (MRI) and ultrasound imaging of peripheral nerve, such that these imaging modalities are increasingly invaluable to the diagnosis of patients with peripheral nerve disorders. Peripheral nerve imaging provides information which is supplementary to clinical and electrodiagnostic diagnosis. Both MRI and ultrasound have particular benefits in specific clinical circumstances and can be considered as complementary techniques. These technologic developments in peripheral nerve imaging will usher in an era of multimodality assessment of peripheral nerve disorders, with clinical evaluations supported by anatomic information from imaging, and functional information from electrodiagnostic studies. Such a multimodality approach will improve the accuracy and efficiency of patient care.

Quantitative assessment of nerve echogenicity as an additional tool for evaluation of common fibular neuropathy

OBJECTIVE

Quantitative assessment of nerve echogenicity using the MaxEntropy, RenyiEntropy and Yen methods has shown promise in the assessment of ulnar neuropathy at the elbow. The purpose of this study was to determine the clinical usefulness of quantitative echogenicity measurement when using these three automatic thresholding methods in the evaluation of patients with common fibular (CF) neuropathy.

METHODS

High-resolution ultrasonography (HRUS) images of the CF nerve from 45 patients with CF neuropathy were compared to 42 healthy controls.

RESULTS

With all three methods patients with CF neuropathy had significantly higher mean hypoechoic fraction than healthy controls at the level of the fibular head (FH): MaxEntropy 87.4% versus 71.9% (p<0.001), RenyiEntropy 84.7% versus 68% (p<0.001) and Yen 87.6% versus 68.2% (p<0.001). Patients with CF neuropathy could be differentiated from healthy controls at a hypoechoic fraction cut-off point of 82% (MaxEntropy), 80% (RenyiEntropy) and 80% (Yen) with a sensitivity of 82%, 82% and 84% respectively, and a specificity of 93%, 95% and 83% respectively. Similar results were found for sonographic measurements above the FH.

CONCLUSION

Quantitative assessment of nerve echogenicity using the MaxEntropy, RenyiEntropy and Yen methods can be used to distinguish between patients with CF neuropathy and healthy controls with high sensitivity and specificity.

SIGNIFICANCE

These three proven automatic thresholding methods can be used to assess nerve echogenicity in future studies. Quantitative echogenicity assessment with HRUS shows promise for the future as a potential diagnostic tool in daily clinical practice.

High-resolution ultrasound of peripheral nerves in systemic sclerosis: a pilot study of computer-aided quantitative assessment of nerve density

OBJECTIVES

To quantitatively evaluate and compare nerve density in patients with limited cutaneous systemic sclerosis (lcSSc) and control subjects using high-resolution ultrasound (US) with a computer-aided assessment.

METHODS

Forty patients and 40 age- and sex-matched control subjects were prospectively enrolled. Ultrasound (US) examination (17-5 MHz probe) of the median nerve at the elbow was performed bilaterally by one radiologist. A software quantified the ratio between the hypoechoic and hyperechoic areas of peripheral nerves on ultrasound. Two observers set the threshold in the images acquired, and three observers performed the digital analysis of nerve density. Statistical analysis included Mann-Whitney U-test of patients versus control subjects and subgroup analysis of symptomatic and non-symptomatic patients. Intra and inter-observer agreement of the three observers were assessed with the kappa statistic.

RESULTS

In all, 160 median nerves were evaluated. According to the US, nerve density was significantly reduced in lcSSc patients compared to control subjects (mean and standard deviation: 41 ± 3 vs 56 ± 4, p < 0.01). Subgroup analysis showed that symptomatic patients (n = 15) had reduced nerve density compared to non-symptomatic (n = 25) patients (39 ± 5 vs 43 ± 4, p < 0.01). Intra-observer agreement was very good (K = 0.82). Inter-observer agreements were good: reader 1 vs reader 2: k = 0.78 (95% confidence interval 0.65 to 0.91); reader 2 vs reader 3: k = 0.72 (95% confidence interval 0.65 to 0.82); reader 3 vs reader 1: k = 0.71 (95% confidence interval 0.64-0.81).

CONCLUSIONS

In lcSSc patients, nerve density was reduced, especially in the symptomatic group, compared to control subjects.

Peripheral Nerve Ultrasound in Small Fiber Polyneuropathy

Routine nerve conduction studies are normal in patients with small fiber neuropathy (SFN), and a definitive diagnosis is based on skin biopsy revealing reduced intra-epidermal nerve fiber density (IENFD). In large fiber polyneuropathy, ultrasound (US) parameters indicate enlargement in cross-sectional area (CSA). This study was aimed at determining if similar changes in large fibers on US are apparent in patients with SFN. Twenty-five patients with SFN diagnosed by reduced IENFD and 25 age- and body mass index (BMI)-matched healthy controls underwent US studies of sural and superficial peroneal sensory nerves. The mean CSA of the sural nerve in SFN patients was 3.2 ± 0.8 mm(2), and in controls, 2.7 ± 0.6 mm(2) (p < 0.0070), and this was independent of sex. There was no difference in the thickness-to-width ratio or echogenicity of the nerves. US of the sural nerve in patients diagnosed with small fiber neuropathy reveals an enlarged cross-sectional area similar to that in large fiber polyneuropathy.

Ultrasound in the diagnosis of peripheral neuropathy: structure meets function in the neuromuscular clinic

Peripheral nerve ultrasound (US) has emerged as a promising technique for the diagnosis of peripheral nerve disorders. While most experience with US has been reported in the context of nerve entrapment syndromes, the role of US in the diagnosis of peripheral neuropathy (PN) has recently been explored. Distinctive US findings have been reported in patients with hereditary, immune-mediated, infectious and axonal PN; US may add complementary information to neurophysiological studies in the diagnostic work-up of PN. This review describes the characteristic US findings in PN reported to date and a classification of abnormal nerve US patterns in PN is proposed. Closer scrutiny of nerve abnormalities beyond assessment of nerve calibre may allow for more accurate diagnostic classification of PN, as well as contribute to the understanding of the intersection of structure and function in PN.

Nerve Ultrasound in Peripheral Neuropathies: A Review

Peripheral neuropathies are one of the most common reasons for seeking neurological care in everyday practice. Electrophysiological studies remain fundamental for the diagnosis and etiological classification of peripheral nerve impairment. The recent technological development though of high resolution ultrasound has allowed the clinician to obtain detailed structural images of peripheral nerves. Nerve ultrasound mainly focuses on the evaluation of the cross sectional area, cross sectional area variability along the anatomical course, echogenity, vascularity and mobility of the peripheral nerves. An increase of the cross sectional area, hypervascularity, disturbed fascicular echostructure and reduced nerve mobility are some of the most common findings of entrapments neuropathies, such as the carpal or cubital tunnel syndrome. Both the cross-sectional area increase and the hypervascularity detected with the Doppler technique seem to correlate significantly with the clinical and electrophysiological severity of the later mononeuropathies. Significantly greater cross sectional area values of the clinically affected cervical nerve root are often detected in cases of cervical radiculopathy. In such cases, the ultrasound findings seem also to correlate significantly with disease duration. On the other hand, multifocal cross sectional area enlargement of cervical roots and/or peripheral nerves is often documented in cases of immune-mediated neuropathies. None of the later pathological ultrasound findings seem to correlate significantly with the electrophysiological parameters or the functional disability. The aim of this review is to provide a timely update on the role of neuromuscular ultrasound in the diagnostic of the most common entrapment and immune-mediated peripheral neuropathies in clinical practice.

Peripheral nerves and plexus: imaging by MR-neurography and high-resolution ultrasound

PURPOSE OF REVIEW

The purpose of this study is to review advances in magnetic resonance (MR)-neurography and nerve-ultrasound for the precise visualization and localization of nerve lesions not only in nerve trauma or mass lesions, but also in entrapment-related and spontaneously occurring intrinsic neuropathies. These advances may improve the understanding and classification of peripheral neuropathies.

RECENT FINDINGS

Diagnostic studies of MR-neurography and high-resolution ultrasound in entrapment-neuropathies consistently report accurate determination and localization of symptomatic nerve entrapment. Additionally, the longitudinal sampling of nerve-T2-signal over larger areas of coverage has become technically feasible. With this approach, more complex patterns of spatial lesion dispersion in nonfocal neuropathies could be observed with reliable lesion image contrast at the level of individual nerve fascicles. Imaging detection of fascicular lesions allows for more accurate localization, because fascicular lesion types represent a specific pitfall for clinical-electrophysiological examinations. Fascicular hypoechogenicity of high-resolution ultrasound is the correlate of nerve-T2-signal lesions, but contrast is inferior and difficult to quantify. Therefore, nerve enlargement remains the main diagnostic criterion in high-resolution ultrasound. Diffusion-tensor-MR-neurography provides quantitative estimates of fiber structure, which were shown to correlate with aging and focal entrapment.

SUMMARY

High-resolution nerve imaging with extended anatomical coverage is feasible and improves the topographic description of spatial lesion dispersion which is particularly relevant for the discrimination between focal and nonfocal neuropathies.

Distinctive patterns of sonographic nerve enlargement in Charcot-Marie-Tooth type 1A and hereditary neuropathy with pressure palsies

OBJECTIVE

The extent of sonomorphologic differences of peripheral nerves between CMT and HNPP is unknown.

METHODS

We recruited 9 patients with CMT-1A and 9 with HNPP. Patients underwent a standardized sonographic protocol, which evaluated nerve size and vascularization. We quantitatively assessed fascicle size and echogenicity.

RESULTS

All 18 patients demonstrated nerve enlargement, but no increased vascularization. HNPP demonstrated larger nerves at sites of entrapment (median nerve at the carpal tunnel p=0.049, ulnar nerve at the sulcus p<0.001), greater swelling ratios of median (p<0.001), ulnar (p=0.017) and fibular nerve (p=0.005) than CMT-1A. CMT-1A revealed larger nerves proximal to sites of entrapment (median and fibular nerve, brachial plexus p<0.001). Nerve fascicles where larger (p<0.001) and more hypo-echogenic in CMT-1A. Nerve, fascicle size nor echogenicity correlated with age, gender or MRC sum-score.

CONCLUSIONS

Ultrasonography of nerves reveals specific phenotypes differentiating CMT-1A from HNPP. In CMT-1A enlargement of nerves and fascicles is multifocal among multiple nerves, whereas in HNPP nerve enlargement is restricted to sites of entrapment.

SIGNIFICANCE

Our findings of specific sonomorphological phenotypes, differentiating CMT-1A from HNPP, may help to improve our pathophysiological insights in CMT and HNPP.

Fascicular ratio: a new parameter to evaluate peripheral nerve pathology on magnetic resonance imaging: a feasibility study on a 3T MRI system

The objective of the study was to define and quantitatively evaluate the fascicular ratio (FR) on magnetic resonance imaging (MRI) in patients with peripheral neuropathies compared with healthy controls. Forty control subjects (20 women, 20 men; age, 44.6 ± 13.4 years) and 40 patients with peripheral neuropathy (22 women, 18 men; age, 50.3 ± 10.2 years) were examined with a standard 3T MRI protocol. With customized software (with semiautomatic and automatic interface), the hypointense and hyperintense areas of the peripheral nerves corresponding to fascicular and nonfascicular tissue were examined on T1-weighted sequences. The ratio of fascicular pixels to total pixels was called FR. Correlation with FR calculated on high-resolution ultrasound was performed. The statistical analysis included the Mann-Whitney U test of controls versus patients, the receiver operating characteristic (ROC) analysis, and the subgroup analysis of patients according to etiologies of neuropathy. Intraobserver and interobserver agreement was calculated based on the evaluation made by 3 readers. Finally, a complete automatic evaluation was performed. On MRI, FRs were significantly increased in patients compared with controls (FR, 76.7 ± 15.1 vs 56 ± 12.3; P < 0.0001 for the semiautomatic interface; and FR 66.3 ± 17.5 vs 47.8 ± 18.4; P < 0.0001 for the automatic interface). The increase in FR was caused mainly by an increase in the hypointense part of the nerve. This observation was valid for all causes of neuropathies. ROC analysis found an area under the curve of 0.75 (95% confidence interval, 0.44-0.81) for FR to discriminate neuropathy from control. The correlation coefficient between MRI and ultrasound was significant (r = 0.49; 95% confidence interval for r, 0.21-0.70; P = 0.012). With the semiautomated evaluation, the mean intraobserver agreement was good (K = 0.86). The interobserver agreements were also good (reader 1 vs reader 2, k = 0.71; reader 2 vs reader 3, k = 0.78; reader 3 vs reader 1, k = 0.71). There were no statistically significant differences between the results obtained using the 2 methods. FR calculation on MRI is feasible, and it may be used in adjunct to standard MRI evaluation in peripheral nerve disorders.