Imaging of Peripheral Nerves: AJR Expert Panel Narrative Review.

Peripheral nerve imaging provides information that can be critical to the diagnosis, staging, and management of peripheral neuropathies. MRI and ultrasound are the imaging modalities of choice for clinical evaluation of the peripheral nerves given their high soft tissue contrast and high resolution, respectively. This AJR Expert Panel Narrative Review describes MRI- and ultrasound-based techniques for peripheral nerve imaging; highlights considerations for imaging in the settings of trauma, entrapment syndromes, diffuse inflammatory neuropathies, and tumor; and discusses image-guided nerve interventions, focusing on nerve blocks and ablation.

Association Between Patellar Tendon Abnormality and Land-Jump Biomechanics in Male Collegiate Basketball Players During the Preseason.

Background: Patellar tendinopathy is a degenerative condition that predominantly affects jumping athletes. Symptoms may be subtle or nonexistent at preseason, but structural abnormalities may be present. Assessing patellar tendon abnormality (PTA) through magnetic resonance imaging (MRI) and ultrasound (US) and classifying symptoms using the Victorian Institute for Sport Assessment-Patellar tendon (VISA-P) may provide useful insights if combined with biomechanics measurements. Purpose: To (1) assess whether land-jump biomechanical patterns are associated with clinically pertinent PTA as seen on imaging and through VISA-P scores and (2) model the contributing risk and accuracy of biomechanics to classify PTA and symptomatic observations. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 26 National Collegiate Athletic Association Division I and II male basketball players (n = 52 limbs) were recruited during the preseason. We collected VISA-P scores, bilateral PTA through US and MRI morphology measurements, and bilateral 3-dimensional lower extremity kinematics and kinetics measurements from a land-jump test from an 18-inch-high (45.7-cm-high) box. Statistically, each limb was treated independently. The association of biomechanics with PTA and symptoms (VISA-P score <80) was tested with multivariate models and post hoc tests. Logistic regression modeled relative risk and accuracy of biomechanical variables to classify PTA and symptomatic limbs. Results: There were 19 to 24 limbs with PTA depending on US and MRI measurements. Differences in hip and knee kinematic strategies and ground-reaction loads were associated with PTA and symptomatic limbs. Peak landing vertical ground-reaction force was significantly decreased (169 ± 26 vs 195 ± 29 %body weight; P = .001), and maximum hip flexion velocity was significantly increased (416 ± 74 vs 343 ± 94 deg/s; P = .005) in limbs with versus without PTA on imaging. Knee flexion at the initial contact was decreased in symptomatic versus healthy limbs (17°± 5° vs 21°± 5°, respectively; P = .045). Regression models classified PTA limbs and symptomatic limbs with 71.2% to 86.5% accuracy. Hip and knee maximum flexion velocity and vertical ground-reaction force variables were most common across models observing clinically pertinent PTA. Conclusion: Our findings suggested that functional kinematic and kinetic biomechanical strategies at the hip and knee were associated with PTA, identified on imaging, and symptomatic limbs.

Utilization of shear wave elastography to quantify and predict response to upper extremity botulinum toxin injections in patients with cerebral palsy: A pilot study.

OBJECTIVE: Shear wave elastography (SWE) was used to quantify change in upper extremity muscle stiffness in patients with unilateral spastic cerebral palsy (USCP) following botulinum toxin A (BTX-A) therapy. We hypothesized that SWE measures would decrease following ultrasound-guided BTX-A injection, and correlate with functional improvement. METHODS: SWE measures of BTX-A treated muscles were recorded immediately pre-injection, and at 1-, 3- and 6-months post-injection. At the same timepoints, functional assessment was performed using the Modified Ashworth Scale (MAS), and passive and active range of motion (PROM and AROM) measures. Correlation of SWE with MAS, PROM and AROM, as well as the relationship between change in SWE and change in MAS, PROM and AROM was determined using Spearman's rank correlation coefficient and generalized estimating equation modeling. RESULTS: 16 muscles were injected and longitudinally assessed. SWE and MAS scores decreased following BTX-A injection (p = 0.030 and 0.004, respectively), reflecting decreased quantitative and qualitative muscle stiffness. Decreased SWE reached statistical significance at 1- and 3-months, and 1-, 3- and 6-months for MAS. When comparing relative change in SWE to relative change in AROM, larger change in SWE strongly correlated with positive change in AROM (p-value range:<0.001-0.057). BTX-A responders also demonstrated lower baseline SWE (1.4 m/s) vs. non-responders (1.9 m/s), p = 0.035. CONCLUSION: Ultrasound-guided BTX-A injections in patients with USCP resulted in decreased quantitative and qualitative muscle stiffness. Strong correlation between change in SWE and AROM, as well as the significant difference in baseline SWE for BTX-A responders and non-responders, suggests SWE may provide a useful tool to predict and monitor BTX-A response.

Sonographic Assessment of Hand Injuries: Diagnostic Accuracy and Review of Pathology.

Background: The high soft-tissue contrast of magnetic resonance imaging (MRI) makes it useful for evaluation of hand injuries, but its limitations include cost, imaging artifacts, and patient claustrophobia. Ultrasound is readily available, fast, noninvasive, and radiation free, but its utility for the evaluation of hand soft-tissue injury and pathology is less well known. Purpose: We sought to examine the accuracy of ultrasound for the evaluation of hand injury at a single institution. Methods: We queried a radiology information system for ultrasound cases between 2014 and 2020 at a tertiary care institution using the keyword "hand" and injury terms. We performed a retrospective chart review of cases found according to the type of injury detected on ultrasound. To evaluate the diagnostic accuracy of ultrasound in hand injury and pathology, we recorded postimaging clinical diagnoses and surgical findings. Results: We found 154 patients who underwent ultrasound for hand injuries and had confirmed surgical diagnosis and/or robust clinical follow-up. Tendon injury was the most commonly diagnosed condition on ultrasound (70/154); others detected were retained foreign body (31), mass (21), ligamentous injury (9), pulley injury (8), nerve injury (11), and traumatic arthropathy (4). Ultrasound correctly characterized hand injury in 150/154 cases (97.4%) based on surgical and/or clinical follow-up. Ultrasound failed to diagnose 3 cases of partial tendon tear and 1 case of digital nerve injury. Conclusion: In this retrospective, single-institution review, ultrasound was found to be highly accurate in the detection of soft tissue hand injury and pathology, demonstrating a high concordance rate with surgical and clinical findings. Further study is warranted.

Sonographic Changes in the Median Nerve Predict Conversion to Surgery after Corticosteroid Injection of the Carpal Tunnel.

BACKGROUND: Risk factors for conversion to surgical management of moderate severity carpal tunnel syndrome are poorly understood. The authors hypothesized that sonographic findings along the carpal tunnel could predict failure of conservative management for carpal tunnel syndrome. METHODS: The authors report on 96 wrists with moderate clinical signs and symptoms of carpal tunnel syndrome. Sonographic evaluation with measurement of median nerve cross-sectional area was performed at three consistent anatomic locations. The authors recorded median nerve morphology, inlet and outlet dimensions of the carpal tunnel, and maximal thickness of the transverse carpal ligament. Steroid injection was performed. Patients were followed up for a minimum of 1 year after injection and progression to surgical management was recorded. RESULTS: A total of 54 percent ( n = 52) of patients converted to surgical management within 1 year after injection. Median nerve cross-sectional area decreased over the course of the carpal tunnel from proximal to distal in 81 of 96 wrists. A greater decrease in cross-sectional area of the median nerve between the pisiform and the hamate was associated with conversion to operative intervention for carpal tunnel syndrome, with the average decrease in median nerve cross-sectional area among those whose conservative treatment failed being 5.01 mm 2 compared with 2.97 mm 2 among those who did not progress to surgical treatment. CONCLUSIONS: This study demonstrates that ultrasound may be an additional tool used by clinicians to better counsel patients about the severity and progression of their disease. Patients who demonstrate a decrease in cross-sectional area of the median nerve along the carpal tunnel demonstrate a higher likelihood of progression to operative management. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

High resolution ultrasound for the evaluation of radial nerve pathology adjacent to metallic hardware.

Accurate localization and characterization of peripheral nerve injuries adjacent to metallic hardware is difficult with magnetic resonance imaging (MRI) due to susceptibility artifact. This study sought to present the use of high-resolution ultrasound (US) in accurate characterization of radial nerve injury adjacent to metallic hardware, using findings at the time of operative exploration as confirmation of the US assessment. A retrospective chart review of cases with clinically identified radial nerve injuries evaluated by the high-resolution US was performed from January 2015 through December 2019. Preoperative clinical data, US reports, MRI reports, electrodiagnostic (EDx) reports, and operative reports were reviewed for each case. Preoperative US correctly characterized the affected nerve component, type, and location of injury in all 13 cases (100%), when correlated with intraoperative findings. Nerve injury was directly adjacent to metallic hardware in 12 cases (92%). Out of the seven cases evaluated by both US and MRI, US correctly accurately diagnosed radial nerve injuries in all cases, whereas MRI accurately diagnosed in four cases (57%). In 3/7 cases (43%) MRI was nondiagnostic due to susceptibility artifact. MRI evaluation of the nerve was limited to some degree by metallic artifact in 6/7 cases (85%).

Utility of lavage in addition to native fluid collection during fluoroscopically guided joint aspiration in infection diagnosis.

Image-guided prosthetic joint aspirations have been criticized in the literature as having poor sensitivity and specificity. Native fluid is typically analyzed for the presence of infection. Joint lavage during fluoroscopically guided aspiration of prosthetic joints is not routinely performed, and the lavage aspirate is not typically analyzed unless native fluid could not be aspirated for culture. This study aims to determine if concordance of culture results from native fluid and an additional joint lavage sample improves sensitivity and specificity in the diagnosis of prosthetic joint infection by fluoroscopically guided joint aspiration. A retrospective review of the fluoroscopically guided joint aspirations at our institution between December 2007 and December 2009 was performed. Data collected from the electronic medical record included culture results for both native fluid and lavage aspirate, histopathology results, final clinical diagnosis, as well as clinical/surgical management. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and likelihood ratio for infection were calculated for the following culture analysis scenarios: native fluid alone; lavage aspirate alone; native fluid; and lavage aspirate. Five hundred sixty-three aspirations, mostly prosthetic joints, were identified in the reviewed time period, of which 397 were sent for both native fluid and lavage aspirate analysis. Concordance between positive culture results from native fluid and joint lavage aspirate markedly increased the likelihood ratio for infection from 23.8 to 138.7 and improved specificity and PPV of fluoroscopically guided joint aspiration, with similar sensitivity and NPV to that of native fluid culture alone.

Quantitative assessment of change in upper extremity muscle stiffness following fluid injection using shear wave elastography.

OBJECTIVE: To quantitatively assess changes in muscle stiffness following intramuscular saline injection using shear wave elastography (SWE). MATERIALS AND METHODS: Thirty muscles (lateral deltoid (LD), biceps brachii (BB), brachialis, pronator teres (PT), flexor carpi radialis (FCR), flexor carpi ulnaris (FCU)) from fresh-frozen cadaveric specimens were injected with saline under ultrasound guidance. Pre- and post-injection muscle thickness (MT) (mm) and SWE (kPa) measurements were recorded. RESULTS: All muscles demonstrated a decrease in the mean SWE value post-injection, with the largest differences ± standard error noted in the LD (14.76 ± 3.55 kPa, p = 0.021) and brachialis muscles (12.02 ± 2.51 kPa, p = 0.013). Muscle thickness increased following injection, although the degree of changes poorly correlated with the change in SWE. CONCLUSION: In summary, following intramuscular injection of saline injection, a decrease in upper extremity muscle stiffness is detected using SWE. It is important to note that if performing a longitudinal assessment of muscle stiffness after intramuscular injection, saline will likely contribute to a decrease in muscle stiffness in the immediate post-injection time period.

Association of Clinical Assessments of Hand Function and Quantitative Ultrasound Metrics in First Carpometacarpal Osteoarthritis.

BACKGROUND: Thumb carpometacarpal (CMC) osteoarthritis (OA), a degenerative condition affecting hand use, is typically evaluated through radiographs and clinical examination. Although this can determine treatment, it is difficult to evaluate functional limitations. Shear wave elastography (SWE) is a quantitative ultrasound technique that characterizes tissue stiffness. QUESTIONS/PURPOSES: This pilot study aimed to establish data of the SWE findings in the thenar eminence muscles in patients with first CMC OA and correlate these findings with the clinical tests of hand function. METHODS: This cross-sectional study correlated the SWE stiffness of thenar eminence muscles to clinical tests of hand function in patients with first CMC OA and in asymptomatic control subjects, using Spearman's correlation coefficient. Mean SWE values of the thenar eminence muscles in patients were compared with those in control subjects. The study was performed in a non-profit tertiary care hospital setting. Patients and control subjects were recruited on a volunteer basis. RESULTS: SWE values in the abductor pollicis brevis and flexor pollicis brevis muscles showed moderate to very strong correlation with multiple measures of hand function. Mean SWE values of the thenar eminence muscles in first CMC OA patients were lower than those in asymptomatic control subjects. CONCLUSIONS: Correlations between mean SWE values in the thenar eminence muscles and clinical measures of hand function suggest decreased function in subjects with less stiff thenar eminence muscles.

Ultrasound imaging of nerves in the neck: Correlation with MRI, EMG, and clinical findings.

OBJECTIVE: We evaluated the performance of ultrasound in the detection of neuropathy of the suprascapular nerve (SSN), long thoracic nerve (LTN), spinal accessory nerve (SAN), and phrenic nerve and compared this performance with MRI. METHODS: A retrospective review of 56 patients who had undergone ultrasound imaging of the SSN, LTN, SAN, and phrenic nerve was performed. Diagnoses made by ultrasound, MRI, EMG reports, and clinical and operative notes were recorded. RESULTS: Ultrasound was successful in visualizing nerves in the neck in the overwhelming majority of cases. Sonographic findings were typically in agreement with MRI and clinical findings. CONCLUSION: Ultrasound is effective in the visualization and diagnostic evaluation of the SSN, LTN, SAN, and phrenic nerve. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that ultrasound can effectively visualize and diagnose neuropathy of the SSN, LTN, SAN, and phrenic nerve in the neck.

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 (ß 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.

Clinical tests for assessing the presence and quality of the palmaris longus tendon: diagnostic accuracy of examination compared with ultrasound.

Various clinical tests are used to evaluate the palmaris longus tendon, but their accuracy is unknown. We assessed the accuracy of clinical tests (Schaeffer's, Thompson's, Mishra-I, Mishra-II) against ultrasound as the reference standard. We hypothesized that Schaeffer's was most accurate and that examination can reliably assess the palmaris longus tendon's length. Ninety-six wrists were examined clinically and evaluated with ultrasound by radiologists who were blinded to examination results. We calculated diagnostic accuracy and agreement between length measurements. Sensitivity values were as follows: Schaeffer's 94%, Mishra-I 100%, Mishra-II 100%, Thompson's 72%. Specificity values were as follows: Schaeffer's 94%, Mishra-I 83%, Mishra-II 89%, Thompson's 91%. Intraclass correlation coefficient between palmaris longus tendon length measurement on examination and ultrasound was 0.54. Schaeffer's test accurately detected this tendon with >90% sensitivity and specificity, but clinical examination less reliably measured palmaris longus tendon length. Ultrasound may be a useful adjunct to assess potential graft length preoperatively. Level of evidence: I.

Fascicular constrictions above elbow typify anterior interosseous nerve syndrome.

INTRODUCTION: In this study we tested the hypothesis that fascicular constrictions (FCs) of the median nerve proximal to the elbow joint characterize anterior interosseous nerve syndrome (AINS). METHODS: Magnetic resonance neurography (MRN) and ultrasound (US) examinations were evaluated in 45 patients with clinically suspected AINS. All 22 patients at site 1 underwent MRN and 8 underwent US; all 23 patients at site 2 underwent US. RESULTS: Median nerve FCs were identified in all MRN cases; FCs and/or fascicular enlargements were identified in 88% of US cases. Most FCs were in the mediannerve posterior/posteromedial region and were proximal to the elbow joint line (mean distance: MRN, 5.4 cm; US, 7.5 cm), with the exception of a single FC (located 1 cm distal). No extrinsic compression of median or anterior interosseous nerves was identified in the arm or forearm. DISCUSSION: AINS is a noncompressive neuropathy characterized by median nerve FCs in the arm.

Clinical Assessments of Hand Function in First Carpometacarpal Osteoarthritis Do Not Appear to Correlate with Radiographic Findings.

BACKGROUND: Thumb carpometacarpal (first CMC) osteoarthritis (OA), a degenerative process affecting hand use, is typically assessed by clinical examination and radiographs. This assessment determines treatment, but it may not reflect functional limitations. QUESTIONS/PURPOSES: We aimed to explore the relationship between measures of hand function and radiographs in individuals with and without first CMC OA. METHODS: We designed a cross-sectional, observational pilot study, enrolling five patients with first CMC OA (nine thumbs with modified Eaton-Littler grades ranging from 1 to 4, using retrospective radiographic data) and nine healthy controls. They underwent evaluation of hand function using four patient-reported outcome measures (PROMs)-the Patient-Specific Functional Scale (PSFS); the Patient-Rated Wrist/Hand Evaluation (PRWHE); the Disabilities of the Arm, Shoulder, and Hand (DASH); and the Modified Score for the Assessment and Quantification of Chronic Rheumatoid Affections of the Hands (M-SACRAH)-and one performance measure, the Arthritis Hand Function Test (AHFT). Spearman's ρ with 95% subject clustered bootstrapped confidence intervals was calculated to assess for correlations between radiographic findings and measures of hand function. RESULTS: Only the DASH work score showed strong positive correlation with radiographic OA grade, with PSFS, PRWHE, M-SACRAH, and AHFT scores demonstrating low to moderate correlations. Notable differences were found between patients and control subjects in median scores of the DASH, PSFS, PRWHE, and M-SACRAH, as well as in the grip, pinch, and button scores of the AHFT. CONCLUSION: While only the DASH work score strongly correlated with radiographic grade of first CMC OA, several measures detected considerable differences in functional hand use between patients and control subjects. The findings of this pilot study suggest that hand function scores be considered in addition to radiographs when determining severity of first CMC OA. The findings can also inform the design of a larger, powered study.

Ultrasound imaging of brachial plexus trauma in gunshot injury.

INTRODUCTION: Brachial plexus trauma related to gunshot (GS) injury requires early examination and characterization to ensure appropriate treatment. Magnetic resonance imaging (MRI) may be contraindicated when there are metal fragments in a patient's body. Ultrasound (US) may present an alternative to imaging GS-related brachial plexus injury. METHODS: Three patients with GS-related brachial plexus injury who underwent US imaging evaluation at our institution were identified. A retrospective review of the patients' medical records was performed. RESULTS: US characterization of nerve abnormalities after GS injury to the brachial plexus was in agreement with electrodiagnostic and intraoperative findings. DISCUSSION: Information from the US reports was useful in preparation for brachial plexus reconstruction surgery. As such, US has unique utility when MRI cannot be performed. US imaging can provide useful characterization of the brachial plexus after GS injury when performed by an experienced operator. Muscle Nerve 59:707-711, 2019.

Ultrasound Imaging of the Brachial Plexus and Nerves About the Neck.

This review describes techniques for sonographic evaluation of the brachial plexus and multiple regional nerve branches in the neck, essential for successful implementation of neurosonology in the neck. High-frequency ultrasound transducers have the ability to produce superior, high-resolution images, allowing for superb depiction of nerve fascicular anatomy. Sonographic appearances of normal nerve anatomy and nerve-specific pathology are reviewed. Benefits and limitations of ultrasound nerve imaging compared with magnetic resonance imaging are discussed.

Sonographic Evaluation of Superficial Peroneal Nerve Abnormalities.

OBJECTIVE: The objective of this study was to review the anatomy of the superficial peroneal nerve (SPN) and describe the sonographic appearances of various abnormalities affecting it. We performed a retrospective chart review of ultrasound (US) examinations of the SPN performed from 2014 to 2016. CONCLUSION: SPN abnormalities are well shown on US. Of 181 patients examined with US, the most commonly detected abnormality was scar encasement and neuroma or laceration.

Ultrasound determination of presence, length and diameter of the palmaris longus tendon.

Inadvertent median nerve harvest is a devastating complication of palmaris longus harvest. Accurate assessment of palmaris longus presence and dimensions preoperatively would minimize this risk and assure safe harvest. We hypothesized that ultrasound would accurately predict palmaris longus presence, length and diameter. Seventeen cadaveric forearms were studied using a LOGIQ-E9 ultrasound. Two radiologists assessed palmaris longus presence and dimensions. Each wrist was explored, and the tendon was harvested and measured. Inter-rater reliability and agreement between measurements was assessed. The palmaris longus was present in 13 of 17 forearms. Both radiologists correctly identified the tendon and its absence (sensitivity and specificity, 100%). Ultrasound assessment of palmaris longus dimensions significantly correlated with surgical measurements. Intraclass correlation coefficient between radiologists was 0.97. We conclude that ultrasound can determine palmaris longus presence and dimensions with excellent accuracy and inter-observer reliability. Ultrasound is useful for preoperative evaluation of the palmaris longus and its use will increase patient safety.