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.

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.

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.

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.

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.

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.

Quantitative Ultrasound Assessment of the Achilles Tendon Under Varied Loads.

This Institutional Review Board-approved pilot study attempted to detect the correlation between ultrasound shear wave elastographic measures and tendon loads. Five male fresh-frozen cadaveric Achilles tendons were loaded in 10-N increments from 0 to 60 N. Shear wave velocity measurements within each Achilles tendon were obtained at each load in longitudinal and transverse orientations. Shear wave velocity measurements were correlated with tendon tension on both longitudinal and transverse plane imaging and showed moderate and strong positive correlation coefficients, respectively. Of note, limitations of the clinically available shear wave elastographic technology for measuring high velocities exist.

Tarsometatarsal joint communication during fluoroscopy-guided therapeutic joint injections and relationship with patient age and degree of osteoarthritis.

OBJECTIVE: Although the tarsometatarsal joints are separated into three distinct synovial compartments, communications between adjacent compartments are often noted during image-guided injections. This study aims to determine whether abnormal inter-compartment tarsometatarsal joint communication is associated with patient age or degree of tarsometatarsal osteoarthritis. MATERIALS AND METHODS: One hundred forty tarsometatarsal injections were retrospectively reviewed by two radiologists. Extent of inter-compartment communication and degree of osteoarthritis were independently scored. Univariate and multivariable analyses were performed to assess whether the presence of and number of abnormal joint communications were related to age and degree of osteoarthritis. RESULTS: Forty out of 140 tarsometatarsal joints showed abnormal communication with a separate synovial compartment, and 3 of the 40 showed abnormal communication with two separate compartments. On univariate analysis, higher grade osteoarthritis (p < 0.001) and older age (p = 0.014) were associated with an increased likelihood of abnormal inter-compartment tarsometatarsal communication and a greater number of these abnormal communications. On multivariate analysis, the degree of osteoarthritis remained a significant predictor of the presence of (p < 0.001) and number of (p < 0.001) abnormal communications, while the association of age was not statistically significant. There was significant correlation between age and degree of osteoarthritis (p < 0.001). CONCLUSION: Higher grade osteoarthritis increases the likelihood of abnormal inter-compartment tarsometatarsal joint communication and is associated with a greater number of abnormal communications. Diagnostic injection to localize a symptomatic tarsometatarsal joint may be less reliable in the setting of advanced osteoarthritis.

Ultrasound-Guided Subgluteal Sciatic Nerve Perineural Injection: Report on Safety and Efficacy at a Single Institution.

OBJECTIVES: To determine the safety and efficacy of ultrasound (US)-guided subgluteal sciatic nerve injections. METHODS: A retrospective chart review of US-guided subgluteal sciatic nerve injections at our institution was performed. RESULTS: Of 221 US-guided subgluteal sciatic nerve injections, 100% achieved technical success, with no postprocedure complications. Sixty-eight percent of patients with follow-up reported symptom relief. Most patients with no relief had suboptimal preprocedure screening. CONCLUSIONS: With appropriate screening, our technique of US-guided subgluteal sciatic nerve injection is safe and effective.

Ultrasound-Guided Peripheral Nerve Injection Techniques.

OBJECTIVE: Peripheral nerves are well seen using ultrasound (US) imaging, making US an ideal modality for image-guided nerve injections. This article provides a technical guide for common upper and lower extremity peripheral nerve injections, including the median, ulnar, and radial nerves in the upper extremity and the lateral femoral cutaneous, sciatic, common peroneal, tibial, and sural nerves in the lower extremity. CONCLUSION: US is an effective modality for use in common upper and lower extremity peripheral nerve injections. With correct technique, peripheral nerve injections can be performed safely and are useful for both diagnostic evaluation of and therapy for peripheral neuropathy.

Volume and Movement Affecting Flow of Injectate Between the Biceps Tendon Sheath and Glenohumeral Joint: A Cadaveric Study.

OBJECTIVE: The objective of our study was to determine if flow of injectate between the biceps tendon sheath and the glenohumeral joint is a function of injectate volume or of motion of the upper extremity. MATERIALS AND METHODS: Sixteen upper-extremity fresh-frozen cadaveric specimens were used. Initially, three ultrasound-guided biceps tendon sheath injections were performed using 2, 5, and 10 mL of contrast material. Immediately after the injections, the specimens were imaged using CT. If contrast material was not visualized within the glenohumeral joint, the specimen was manipulated for 5 minutes and reimaged using CT to assess for contrast material within the joint. Five separate ultrasound-guided glenohumeral joint injections were also performed using 5 mL (three specimens), 10 mL (one specimen), and 15 mL (one specimen) of contrast material. The specimens underwent CT, and the presence or absence of contrast material in the biceps tendon sheath was documented before and after manipulation. Next, eight additional ultrasound-guided biceps tendon sheath injections were performed using 2 mL (six specimens) and 5 mL (two specimens) of contrast material. RESULTS: The 5- and 10-mL biceps tendon sheath injection specimens and the 5-, 10-, and 15-mL glenohumeral joint specimens showed communicating contrast flow on the initial CT study. Only two of the seven 2-mL biceps tendon sheath injection specimens showed flow of contrast material into the glenohumeral joint from the biceps tendon sheath on the initial CT study; the remaining five specimens showed no communication even after manipulation. CONCLUSION: Communication between the biceps tendon sheath and the glenohumeral joint may be a function of injectate volume rather than patient movement.

Ultrasound-Guided Interventions in the Midfoot and Forefoot.

Pathologic conditions in the midfoot and forefoot may be diagnosed and treated using image-guided intervention. Image-guided techniques to treat arthrosis, tendinopathy, nerve disorders, and other miscellaneous midfoot and forefoot conditions are described, with a focus on sonographic guidance.

Ultrasound-guided perineural injection for nerve blockade: Does a single-sided injection produce circumferential nerve coverage?

PURPOSE: Our current clinical technique for sonographic-guided perineural injection consists of two-sided perineural needle placement to obtain circumferential distribution of the injectate. This study aimed to determine if a single-side needle position will produce circumferential nerve coverage. METHODS: Fresh-frozen cadaveric specimens were used for this study. In six upper extremities, a needle was positioned along the deep surface of median, radial, and ulnar nerves in the carpal tunnel, radial tunnel, and cubital tunnel, respectively, and 2 ml of contrast was injected for each nerve. In three pelvic specimens, a needle was positioned deep to the sciatic nerves bilaterally, and 5 ml of contrast was injected. An additional four median nerve injections were performed using superficial surface needle position. The specimens then underwent CT scanning to assess the distribution of the perineural contrast medium. RESULTS: One hundred percent of the radial, ulnar, and sciatic nerves demonstrated circumferential distribution on CT. Only 50% of the median nerve injections with the needle placed deep to the nerve produced circumferential coverage, whereas 100% of median nerves injected with the needle between the nerve and retinaculum demonstrated circumferential coverage. The average length of spread of perineural injectate was 11.6 cm in the upper extremity and 10.3 cm for the sciatic nerves. CONCLUSIONS: Using clinical volumes of fluid, needle positioning at the deep surface of upper extremity and sciatic nerves was sufficient to produce circumferential coating of the nerve, except in the carpal tunnel, where placement of the needle between the nerve and flexor retinaculum is recommended. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:465-469, 2016.

Granulomatous disease in the head and neck: developing a differential diagnosis.

Granulomatous diseases have a varied etiology that includes autoimmune, infectious, idiopathic, and hereditary causes. The unifying factor in these diseases is the formation of granulomas, which histologically are mononuclear inflammatory cells or macrophages surrounded by lymphocytes. Granulomatous diseases often have systemic manifestations that affect organs throughout the body. Granulomatous diseases with head and neck manifestations include granulomatosis with polyangiitis, Churg-Strauss syndrome, Behçet disease, chronic granulomatous disease, and sarcoidosis. Infectious causes include tuberculosis, cat-scratch disease, syphilis, leprosy, actinomycosis, rhinoscleroma, and fungal infections. In the head and neck, granulomatous disease may affect the orbits, sinonasal cavities, salivary glands, aerodigestive tract, temporal bone, or skull base. Imaging findings include sinonasal opacification, ocular and other soft-tissue masses, osseous erosion, airway narrowing, lymphadenopathy, and salivary gland infiltration. Vascular involvement may also be evident, with displacement, narrowing, or occlusion of arteries and veins. Some radiologic findings of granulomatous processes have a considerable overlap with findings of malignancy, and a radiologic differential diagnosis inclusive of both is critical to avoid incorrect clinical treatment. Without the benefit of a prior clinical diagnosis, laboratory findings, or suggestive clinical signs and symptoms, granulomatous diseases may be difficult to differentiate radiologically. Although individual granulomatous diseases may have overlapping findings at imaging, certain radiologic findings should prompt the inclusion of granulomatous diseases in the differential diagnosis, thus facilitating appropriate clinical management.

Membranous lipodystrophy: skeletal findings on CT and MRI.

Membranous lipodystrophy, also known as Nasu-Hakola disease, is a rare hereditary condition with manifestations in the nervous and skeletal systems. The radiographic appearance of skeletal lesions has been well described in the literature. However, CT and MRI findings of lesions in the bone have not been documented to date. This report describes the radiographic, CT, MRI, and histopathologic skeletal findings in a case of membranous lipodystrophy. With corroborative pathologic findings, a diagnosis of membranous lipodystrophy on imaging allows for appropriate clinical management of disease manifestations.

Ultrasound-guided needle localization to aid foreign body removal in pediatric patients.

Patients with podiatric foreign body injury commonly present to the emergency department. Often, the foreign object cannot be easily located or removed, and radiographs are frequently obtained to aid in localization. In cases requiring tissue dissection to remove the foreign bodies, accurate localization is required for safe removal of small and difficult to visualize bodies. We present 2 pediatric cases in which an ultrasound-guided needle localization technique was used to facilitate successful removal of small, difficult to visualize foreign bodies from the plantar foot. Ultrasound-guided needle localization reduced the required incision length and depth and helped to minimize the risk of damage to surrounding tissue.

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.

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%).