MR Neurography of Peripheral Nerve Injury in the Presence of Orthopedic Hardware: Technical Considerations

Hourglass-like constrictions on MRI are common in electromyography-confirmed cases of neuralgic amyotrophy (Parsonage-Turner syndrome): A tertiary referral center experience

INTRODUCTION/AIMS

Hourglass-like constrictions (HGCs) of involved nerves in neuralgic amyotrophy (NA) (Parsonage-Turner syndrome) have been increasingly recognized with magnetic resonance neurography (MRN). This study sought to determine the sensitivity of HGCs, detected by MRN, among electromyography (EMG)-confirmed NA cases.

METHODS

This study retrospectively reviewed records of patients with the clinical diagnosis of NA, and with EMG confirmation, who underwent 3-Tesla MRN within 90 days of EMG at a single tertiary referral center between 2011 and 2021. "Severe NA" positive cases were defined by a clinical diagnosis and specific EMG criteria: fibrillation potentials or positive sharp waves, along with motor unit recruitment (MUR) grades of "discrete" or "none." On MRN, one or more HGCs, defined as focally decreased nerve caliber or diffusely beaded appearance, was considered "imaging-positive." Post hoc inter-rater reliability for HGCs was measured by comparing the original MRN report against subsequent blinded interpretation by a second radiologist.

RESULTS

A total of 123 NA patients with 3-Tesla MRN performed within 90 days of EMG were identified. HGCs were observed in 90.2% of all NA patients. In "severe NA" cases, based on the above EMG criteria, HGC detection resulted in a sensitivity of 91.9%. Nerve-by-nerve analysis (183 nerve-muscle pairs, nerves assessed by MRN, muscles assessed by EMG) showed a sensitivity of 91.0%. The second radiologist largely agreed with the original HGC evaluation, (94.3% by subjects, 91.8% by nerves), with no significant difference between evaluations (subjects: χ2 = 2.27, P = .132, nerves: χ2 = 0.98, P = .323).

DISCUSSION

MRN detection of HGCs is common in NA.

Iatrogenic "overshoot" nerve injuries: imaging features

OBJECTIVE

Describe features of iatrogenic "overshoot" nerve injuries on ultrasound and MRI, which occur when an instrument passes through the bone and injures the nerve after it penetrates the opposite cortex.

MATERIALS AND METHODS

After a keyword search of the radiology database at a tertiary care orthopedic hospital from January 2016 to December 2022, those fulfilling the inclusion criteria of (1) instrumentation through the bone during surgery, (2) acute neuropathy immediately after surgery, (3) nerve injury confirmed on electrodiagnostics, and (4) imaging consistent with overshoot nerve injury were included. Imaging studies were retrospectively evaluated to determine primary and secondary signs of an overshoot nerve injury.

RESULTS

Six patients (3 females, mean age 26.7 (range 10-49) years) had nerve injury fitting the mechanism of injury: 3 injuries to the radial nerve during fixation of distal humerus fractures, 1 tibial nerve and 1 superficial peroneal nerve injury during fixation of tibial fractures, and 1 posterior interosseous nerve injury during biceps tendon repair. Ultrasounds were performed in all while 4 also had MRI. Secondary signs included (1) cortical defect adjacent to injured nerve (n=2); (2) scar extending from bone to injured nerve (n=2); (3) screw tip pointing to injured nerve (n=1, 4) tract in bone on MRI from previous instrumentation pointing to injured nerve (n=2).

CONCLUSION

In addition to primary signs such as laceration or neuroma, secondary signs of "overshoot" nerve injury include cortical defect, scar extending to nerve, screw tip pointing to nerve, and linear tract in the bone on MRI.

MRI findings correlate with difficult dissection during proximal hamstring repair and with postoperative sciatica

OBJECTIVE

This study examines the correlation between MRI findings and difficult dissection during proximal primary hamstring repair and postoperative sciatica.

MATERIALS AND METHODS

A total of 32 cases of surgically repaired hamstring tendon tears that underwent preoperative and postoperative MRI were divided into sciatica (n = 12) and control (n = 20) groups based on the presence or absence of postoperative sciatica. Cases were scored by two blinded musculoskeletal radiologists for imaging features associated with difficult surgical dissection and the development of subsequent sciatica. Intra- and interrater agreements, as well as correlation of MRI findings with symptoms (odds ratio, OR), were calculated.

RESULTS

On preoperative MRI, diffuse hamstring muscle edema pattern suggestive of active denervation (OR 9.4-13.6), and greater sciatic perineural scar circumference (OR 1.9-2) and length (OR 1.2-1.3) were significantly correlated with both difficult dissection and postoperative sciatica. Preoperatively, a greater number of tendons torn (OR 3.3), greater tear cross-sectional area (CSA, OR 1.03), and increased nerve T2-weighted signal (OR 3.2) and greater perineural scar thickness (OR 1.7) were also associated with difficult dissection, but not postoperative sciatica. On postoperative MRI, hamstring denervation, sciatic nerve tethering to the hamstring tendon, and development of perineural scar and greater perineural scar extent were all significantly correlated with postoperative sciatica.

CONCLUSION

Preoperative hamstring MRI demonstrates findings predictive of difficult sciatic nerve dissection; careful MRI evaluation of the nerve and for the presence and extent of perineural scar is important for preoperative planning. Preoperative and postoperative MRI both depict findings that correlate with postoperative sciatica.

Magnetic resonance imaging of femoral nerve injury in the setting of anterior approach total hip arthroplasty

PURPOSE

To illustrate MRI findings in patients with femoral neuropathy following anterior approach total hip arthroplasty (THA).

METHODS

This was a retrospective review of patients who underwent MRI for femoral neuropathy following anterior approach THA between January 1, 2010, and July 1, 2022. Included patients had no preexisting neurologic condition. Clinical and diagnostic data were collected. MRIs were reviewed in consensus by 2 musculoskeletal radiologists.

RESULTS

A total of 115 patient records were reviewed, 17 of which were included in the final analysis (mean age 64 years; 11 females). Study subjects presented with weakness with hip flexion and knee extension and pain and numbness in the femoral nerve distribution. In 7 subjects, the femoral nerve appeared normal. In 5 subjects, the femoral nerve was hyperintense on fluid-sensitive fat-suppressed imaging. In 4 patients, mass effect on the femoral nerve by either ill-defined soft tissue edema (n = 2), seroma (n = 1), or heterotopic ossification (n = 1) was detected. Only 1 patient had a nerve transection. Patients were imaged at a median time of 8 months (range: 1 day to 11 years) following arthroplasty placement. Clinical follow-up was available in 8 patients, of whom half had complete symptomatic resolution and half had partial improvement at a mean follow-up time of 39.3 months (SD 51.1). Of these 8, 1 underwent revision arthroplasty, 1 had removal of hardware, and another had excision of heterotopic ossification.

CONCLUSION

MRI provides a means to directly evaluate the femoral nerve following anterior approach THA in both the immediate and chronic postoperative periods.

Magnetic Resonance Neurography of the Lumbosacral Plexus

Pain and weakness in the low back, pelvis, and lower extremities are diagnostically challenging, and imaging can be an important step in the workup and management of these patients. Technical advances in magnetic resonance neurography (MRN) have significantly improved its utility for imaging the lumbosacral plexus (LSP). In this article, the authors review LSP anatomy and selected pathology examples. In addition, the authors will discuss technical considerations for MRN with specific points for the branch nerves off the plexus.

Multi-objective property optimisation of a phosphoserine-modified calcium phosphate cement for orthopaedic and dental applications using design of experiments methodology

Phosphoserine is a ubiquitous molecule found in numerous proteins and, when combined with alpha-tricalcium phosphate (α-TCP) powder, demonstrates the ability to generate an adhesive biomaterial capable of stabilising and repairing bone fractures. Design of Experiments (DoE) approach was able to optimise the composition of phosphoserine-modified calcium phosphate cement (PM-CPC) demonstrating that the liquid:powder ratio (LPR) and quantity of phosphoserine (wt%) significantly influenced the handling, mechanical, and adhesion properties. Subsequently, the DoE optimisation process identified the optimal PM-CPC formulation, exhibiting a compressive strength of 29.2 ± 4.9 MPa and bond/shear strength of 3.6 ± 0.9 MPa after a 24 h setting reaction. Moreover, the optimal PM-CPC composition necessitated a mixing time of 20 s and displayed an initial setting time between 3 and 4 min, thus enabling homogenous mixing and precise delivery within a surgical environment. Notably, the PM-CPC demonstrated a bone-to-bone bond strength of 1.05 ± 0.3 MPa under wet conditions, coupled with a slow degradation rate during the first five days. These findings highlight the ability of PM-CPC to effectively support and stabilise bone fragments during the initial stages of natural bone healing. The developed PM-CPC formulations fulfil the clinical requirements for working and setting times, static mechanical, degradation properties, and injectability, enabling surgeons to stabilise complex bone fractures. This innovative bioinspired adhesive represents a significant advancement in the treatment of challenging bone injuries, offering precise delivery within a surgical environment and the potential to enhance patient outcomes. STATEMENT OF SIGNIFICANCE: This manuscript presents a noteworthy contribution to the field of bone fracture healing and fixation by introducing a novel phosphoserine-modified calcium phosphate cement (PM-CPC) adhesive by incorporating phosphoserine and alpha-TCP. This study demonstrates the fabrication and extensive characterisation of this adhesive biomaterial that holds great promise for stabilising and repairing complex bone fractures. Design of Experiment (DoE) software was used to investigate the correlations between process, property, and structure of the adhesive, resulting in a cost-effective formulation with desirable physical and handling properties. The PM-CPC adhesive exhibited excellent adhesion and cohesion properties in wet-field conditions. This research offers significant potential for clinical translation and contributes to the ongoing advancements in bone tissue engineering.

Compressed Sensing SEMAC MRI of Hip, Knee, and Ankle Arthroplasty Implants: A 1.5-T and 3-T Intrapatient Performance Comparison for Diagnosing Periprosthetic Abnormalities

BACKGROUND. The utility of 3-T MRI for diagnosing joint disorders is established, but its performance for diagnosing abnormalities around arthroplasty implants is unclear. OBJECTIVE. The purpose of this study was to compare 1.5-T and 3-T compressed sensing slice encoding for metal artifact correction (SEMAC) MRI for diagnosing peri-prosthetic abnormalities around hip, knee, and ankle arthroplasty implants. METHODS. Forty-five participants (26 women, 19 men; mean age ± SD, 71 ± 14 years) with symptomatic lower extremity arthroplasty (hip, knee, and ankle, 15 each) prospectively underwent consecutive 1.5- and 3-T MRI examinations with intermediate-weighted (IW) and STIR compressed sensing SEMAC sequences. Using a Likert scale, three radiologists evaluated the presence or absence of periprosthetic abnormalities, including bone marrow edema-like signal, osteolysis, stress reaction/fracture, synovitis, and tendon abnormalities and collections; image quality; and visibility of anatomic structures. Statistical analysis included nonparametric comparison and interchangeability testing. RESULTS. For diagnosing periprosthetic abnormalities, 1.5-T and 3-T compressed sensing SEMAC MRI were interchangeable. Across all three joints, 3-T MRI had lower noise than 1.5-T MRI (median IW and STIR scores at 3 T vs 1.5 T, 4 and 4 [range, 2-5 and 3-5] vs 3 and 3 [range, 2-5 and 2-4]; p < .01 for both), sharper edges (median IW and STIR scores at 3 T vs 1.5 T, 4 and 4 [both ranges, 2-5] vs 3 and 3 [range, 2-4 and 2-5]; p < .02 and p < .05), and more effective metal artifact reduction (median IW and STIR scores at 3 T vs 1.5 T, 4 and 4 [range, 3-5 and 2-5] vs 4 and 4 [both ranges, 3-5]; p < .02 and p = .72). Agreement was moderate to substantial for image contrast (IW and STIR, 0.66 and 0.54 [95% CI, 0.41-0.91 and 0.29-0.80]; p = .58 and p = .16) and joint capsule visualization (IW and STIR, 0.57 and 0.70 [range, 0.32-0.81 and 0.51-0.89]; p = .16 and p = .19). The bone-implant interface was more visible at 1.5 T (median IW and STIR scores, 4 and 4 [both ranges, 2-5] at 1.5 T vs 3 and 3 [both ranges, 2-5] at 3 T; p = .08 and p = .58), but periprosthetic tissues had superior visibility at 3 T (IW and STIR, 4 and 4 [both ranges, 3-5] at 3 T vs 4 and 4 [ranges, 2-5 and 3-5] at 1.5 T; p = .07 and p = .19). CONCLUSION. Optimized 1.5-T and 3-T compressed sensing SEMAC MRI are interchangeable for diagnosing periprosthetic abnormalities, although metallic artifacts are larger at 3 T. CLINICAL IMPACT. With compressed sensing SEMAC MRI, lower extremity arthroplasty implants can be imaged at 3 T rather than 1.5 T.

An Updated Review of Magnetic Resonance Neurography for Plexus Imaging

Magnetic resonance neurography (MRN) is increasingly used to visualize peripheral nerves in vivo. However, the implementation and interpretation of MRN in the brachial and lumbosacral plexi are challenging because of the anatomical complexity and technical limitations. The purpose of this article was to review the clinical context of MRN, describe advanced magnetic resonance (MR) techniques for plexus imaging, and list the general categories of utility of MRN with pertinent imaging examples. The selection and optimization of MR sequences are centered on the homogeneous suppression of fat and blood vessels while enhancing the visibility of the plexus and its branches. Standard 2D fast spin-echo sequences are essential to assess morphology and signal intensity of nerves. Moreover, nerve-selective 3D isotropic images allow improved visualization of nerves and multiplanar reconstruction along their course. Diffusion-weighted and diffusion-tensor images offer microscopic and functional insights into peripheral nerves. The interpretation of MRN in the brachial and lumbosacral plexi should be based on a thorough understanding of their anatomy and pathophysiology. Anatomical landmarks assist in identifying brachial and lumbosacral plexus components of interest. Thus, understanding the varying patterns of nerve abnormalities facilitates the interpretation of aberrant findings.

MRI Advancements in Musculoskeletal Clinical and Research Practice

Over the past decades, MRI has become increasingly important for diagnosing and longitudinally monitoring musculoskeletal disorders, with ongoing hardware and software improvements aiming to optimize image quality and speed. However, surging demand for musculoskeletal MRI and increased interest to provide more personalized care will necessitate a stronger emphasis on efficiency and specificity. Ongoing hardware developments include more powerful gradients, improvements in wide-bore magnet designs to maintain field homogeneity, and high-channel phased-array coils. There is also interest in low-field-strength magnets with inherently lower magnetic footprints and operational costs to accommodate global demand in middle- and low-income countries. Previous approaches to decrease acquisition times by means of conventional acceleration techniques (eg, parallel imaging or compressed sensing) are now largely overshadowed by deep learning reconstruction algorithms. It is expected that greater emphasis will be placed on improving synthetic MRI and MR fingerprinting approaches to shorten overall acquisition times while also addressing the demand of personalized care by simultaneously capturing microstructural information to provide greater detail of disease severity. Authors also anticipate increased research emphasis on metal artifact reduction techniques, bone imaging, and MR neurography to meet clinical needs.

"Knowing It Before Blocking It," the ABCD of the Peripheral Nerves: Part D (Approach to the Patient With Nerve Injuries)

"Prevention is always better than cure." However, despite all precautions or preventive measures, sometimes patients develop neurodeficits due to suspected nerve injury in the perioperative period. Assessment and evaluation of the patient's symptoms can provide clues to the causative factors. Such causative factors can be corrected immediately to avoid further deterioration, or some may require further workup. The management plan for such a diagnosed nerve injury depends on the symptoms, the finding of the medical history, and the diagnostic imaging and tests. Simultaneous symptomatic relief in the form of pain medications, steroids, anti-inflammatory drugs, psychological counseling, and reassurance is essential to expedite treatment goals. Diagnosing and treating nerve injuries cannot be laid down as a straightforward part. It is a zigzag puzzle in its own right, playing with time and injury progression. Careful assessment to diagnose the extent of nerve damage plays an important role in treatment plans. It helps decide when to proceed and when to postpone, whether conservative strategies would suffice, or surgical repair would be required. Although most nerve injuries are self-limiting, some cases require surgical intervention that needs to be diagnosed early. The revolution was started by Sunderland in 1945 when he described neurosurgical techniques that drastically changed the entire scenario of nerve repairs. The ultimate effective treatment and full recovery may not be guaranteed, but attempts must be made to achieve the best results. With the patient's interests in mind, it is important to formulate a plan ensuring a good quality of life with minimal impact on their daily activities. Multifactorial nerve injury requires a multidisciplinary approach that primarily includes reassuring, psychological counseling, multimodal analgesia, and neurological and occupational consultations. This article describes the step-by-step approach known as the symptoms categorization-history taking-examination-diagnostic evaluations (SHED) approach to managing patients with peripheral nerve injuries. It also details the various modalities for diagnosing nerve injuries, sequential electrodiagnostic studies, and treatment plans depending on the type and extent of nerve injuries. It will help readers to design a treatment plan based on the patient's symptoms and evaluation results.

Early perioperative magnetic resonance findings in patients with foot drop following total hip Arthroplasty: A descriptive case-series

PURPOSE

This study aims to characterize iatrogenic sciatic nerve injury patterns in the early, perioperative period following posterior-approach total hip arthroplasty (THA) with magnetic resonance imaging (MRI).

METHODS

This was an IRB-approved retrospective analysis of patients acquired from a longitudinal, single site radiology database of patients who underwent MRI for "foot drop" within 4 weeks following posterior-approach THA surgery, over a 20-year period.

RESULTS

MRI exams from 51 patients (mean age 62 years; 32 females) who met inclusion criteria were evaluated. Mean time to MRI was 2.4 days. Of 51 patients, 43 underwent primary THA, 6 revision THA and 2 explantation with antibiotic spacer placement. Ten exams revealed a normal appearance of the sciatic nerve. Nineteen showed compression of the sciatic nerve by edema or a fluid collection, without intrinsic nerve abnormality. Fifteen demonstrated perineural tethering or scar/granulation tissue encasement of the nerve, and in half of these cases the sciatic nerve was enlarged and/or hyperintense on fluid-sensitive sequences. Six patients had sciatic nerve compression secondary to quadratus femoris retraction. Six patients had complete resolution of the foot drop at a mean follow-up of 37.3 months following surgery, and in these cases the sciatic nerve appeared normal on the initial postoperative MRI. Remaining patients all had persistent weakness and paresthesias in the sciatic nerve distribution at a mean follow-up duration of 34.3 months.

CONCLUSION

This retrospective case series demonstrates various sciatic nerve injury patterns in the early perioperative period on MRI and proposes a targeted MRI protocol to evaluate the sciatic nerve post THA surgery.

Imaging of the Peripheral Nerves of the Lower Extremity

Continued advancements in magnetic resonance (MR) neurography and ultrasound have made both indispensable tools for the workup of peripheral neuropathy. Ultrasound provides high spatial resolution of superficial nerves, and techniques such as "sonopalpation" and dynamic maneuvers can improve accuracy. Superior soft tissue contrast, ability to evaluate both superficial and deep nerves with similar high resolution, and reliable characterization of denervation are strengths of MR neurography. Nevertheless, familiarity with normal anatomy, anatomic variants, and common sites of nerve entrapment is essential for radiologists to use both MR neurography and ultrasound effectively.

Pain After Hip Arthroplasty

MR imaging and ultrasound (US) have complementary roles for the comprehensive assessment of painful hip arthroplasty. Both modalities demonstrate synovitis, periarticular fluid collections, tendon tears and impingement, and neurovascular impingement, often with features indicating the causative etiology. MR imaging assessment requires technical modifications to reduce metal artifact, such as multispectral imaging, and optimization of image quality, and a high-performance 1.5-T system. US images periarticular structures at high-spatial resolution without interference of metal artifact, permitting real-time dynamic evaluation, and is useful for procedure guidance. Bone complications (periprosthetic fracture, stress reaction, osteolysis, and component loosening) are well depicted on MR imaging.

Brachial Plexus Magnetic Resonance Neurography: Technical Challenges and Solutions

ABSTRACT

Magnetic resonance neurography of the brachial plexus (BP) is challenging owing to its complex anatomy and technical obstacles around this anatomic region. Magnetic resonance techniques to improve image quality center around increasing nerve-to-background contrast ratio and mitigating imaging artifacts. General considerations include unilateral imaging of the BP at 3.0 T, appropriate selection and placement of surface coils, and optimization of pulse sequences. Technical considerations to improve nerve conspicuity include fat, vascular, and respiratory artifact suppression techniques; metal artifact reduction techniques; and 3-dimensional sequences. Specific optimization of these techniques for BP magnetic resonance neurography greatly improves image quality and diagnostic confidence to help guide nonoperative and operative management.

Quantitative MRI Differentiates Electromyography Severity Grades of Denervated Muscle in Neuropathy of the Brachial Plexus

BACKGROUND

Quantitative MRI (qMRI) metrics reflect microstructural skeletal muscle changes secondary to denervation and may correspond to conventional electromyography (EMG) assessments of motor unit recruitment (MUR) and denervation.

HYPOTHESIS

Differences in quantitative T2 , diffusion-based apparent fiber diameter (AFD), and fat fraction (FF) exist between EMG grades, in patients with clinically suspected neuropathy of the brachial plexus.

STUDY TYPE

Prospective.

POPULATION

A total of 30 subjects (age = 37.5 ± 17.5, 21M/9F) with suspected brachial plexopathy.

FIELD STRENGTH/SEQUENCE

3-Tesla; qMRI using fast spin echo (T2 -mapping), multi-b-valued diffusion-weighted echo planar imaging (for AFD), and dual-echo Dixon gradient echo (FF-mapping) sequences.

ASSESSMENT

qMRI values were compared against EMG grades (MUR and denervation). qMRI values (T2 , AFD, and FF) were obtained for five regional shoulder muscles. A 4-point scale was used for MUR/denervation severity.

STATISTICAL TESTS

Linear mixed models and least-squares pairwise comparisons were used to evaluate qMRI differences between EMG grades. Predictive accuracy of EMG grades from qMRI was quantified by 10-fold cross-validated logistic models. A P value < 0.05 was considered statistically significant.

RESULTS

Mean (95% confidence interval) qMRI for "full" MUR were T2  = 39.40 msec (35.72-43.08 msec), AFD = 78.35 μm (72.52-84.19 μm), and FF = 4.54% (2.11-6.97%). Significant T2 increases (+8.36 to +14.67 msec) and significant AFD decreases (-11.04 to -21.58 μm) were observed with all abnormal MUR grades as compared to "full" MUR. Significant changes in both T2 and AFD were observed with increased denervation (+9.59 to +15.04 msec, -16.25 to -18.66 μm). There were significant differences in FF between some MUR grades (-1.45 to +2.96%), but no significant changes were observed with denervation (P = 0.089-0.662). qMRI prediction of abnormal MUR or denervation was strong (mean accuracy = 0.841 and 0.810, respectively) but moderate at predicting individual grades (accuracy = 0.492 and 0.508, respectively).

DATA CONCLUSION

Quantitative T2 and AFD differences were observed between EMG grades in assessing muscle denervation.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 1.

Neuropathy Score Reporting and Data System (NS-RADS): MRI Reporting Guideline of Peripheral Neuropathy Explained and Reviewed

A standardized guideline and scoring system should be used for the MR imaging diagnosis of peripheral neuropathy. The MR imaging-based Neuropathy Score Reporting and Data System (NS-RADS) is a newly devised classification system (in press in AJR) that can be used to communicate both type and severity of peripheral neuropathy in the light of clinical history and examination findings. The spectrum of neuropathic conditions and peripheral nerve disorders covered in this system includes nerve injury, entrapment, neoplasm, diffuse neuropathy, and post-interventional states. This classification system also describes the temporal MR imaging appearances of regional muscle denervation changes. This review article is based on the multicenter validation study pre-published in American journal of Roentgenology and discusses technical considerations of optimal MR imaging for peripheral nerve evaluation and discusses the NS-RADS classification and its severity scales with illustration of conditions that fall under each classification. The readers can gain knowledge of the NS-RADS classification system and learn to apply it in their practices for improved inter-disciplinary communications and timely patient management.

Neuropathy Score Reporting and Data System: A Reporting Guideline for MRI of Peripheral Neuropathy With a Multicenter Validation Study

Background: A standardized guideline and scoring system would improve evaluation and reporting of peripheral neuropathies on MRI. Objective: The objective of this study was to create and validate a neuropathy classification and grading system, which we named the Neuropathy Score Reporting and Data System (NS-RADS). Methods: This retrospective study included 100 patients with nerve imaging studies and known clinical diagnoses. Experts crafted NS-RADS using mutually agreed-upon qualitative criteria for the classification and grading of peripheral neuropathies. Different classes were created to account for the spectrum of underlying pathologies: unremarkable (U), injury (I), neoplasia (N), entrapment (E), diffuse neuropathy (D), not otherwise specified (NOS), and postintervention state (PI). Subclasses were established to describe the severity or extent of the lesions. Validation testing was performed by 11 readers from multiple institutions with experience levels ranging from 3 to 18 years after residency. After initial reader training, cases were presented to readers, who were blinded to final clinical diagnoses. Interobserver agreement was assessed using correlation coefficients and the Conger kappa, and accuracy testing was performed. Results: Final clinical diagnoses included normal (n = 5), nerve injury (n = 25), entrapment (n = 15), neoplasia (n = 33), diffuse neuropathy (n = 18), and persistent neuropathy after intervention (n = 4). The miscategorization rate for NS-RADS classes was 1.8%. Final diagnoses were correctly identified by readers in 71-88% of cases. Excellent interreader agreement was found on the NS-RADS pathology categorization (κ = 0.96; 95% CI, 0.93-0.98) as well as muscle pathology categorization (κ = 0.76; 95% CI, 0.68-0.82]. The accuracy for determining milder versus more severe categories per radiologist ranged from 88% to 97% for nerve lesions and from 86% to 94% for muscle abnormalities. Conclusion: The proposed NS-RADS classification is accurate and reliable across different reader experience levels and a spectrum of peripheral neuropathy conditions. Clinical Impact: NS-RADS can be used as a standardized guideline for reporting peripheral neuropathies and improved multidisciplinary communications.