Elbow Nerves: MR Findings in 60 Asymptomatic Subjects—Normal Anatomy, Variants, and Pitfalls

Electrodiagnostic studies and new diagnostic modalities for evaluation of peripheral nerve disorders

Electrodiagnostic studies (EDx) are frequently performed in the diagnostic evaluation of peripheral nerve disorders. There is increasing interest in the use of newer, alternative diagnostic modalities, in particular imaging, either to complement or replace established EDx protocols. However, the evidence to support this approach has not been expansively reviewed. In this paper, diagnostic performance data from studies of EDx and other diagnostic modalities in common peripheral nerve disorders have been analyzed and described, with a focus on radiculopathy, plexopathy, compressive neuropathies, and the important neuropathy subtypes of Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), vasculitic neuropathy and diabetic neuropathy. Overall EDx retains its place as a primary diagnostic modality in the evaluated peripheral nerve disorders. Magnetic resonance imaging and ultrasound have developed important complementary diagnostic roles in compressive and traumatic neuropathies and atypical CIDP, but their value is more limited in other neuropathy subtypes. Identification of hourglass constriction in nerves of patients with neuralgic amyotrophy may have therapeutic implications. Investigation of radiculopathy is confounded by poor correlation between clinical features and imaging findings and the lack of a diagnostic gold standard. There is a need to enhance the literature on the utility of these newer diagnostic modalities.

Cubital tunnel syndrome: anatomy, pathology, and imaging

Cubital tunnel syndrome (CuTS) is the second most common peripheral neuropathy in the upper limb. It occurs due to ulnar nerve compression within the fibro-osseous cubital tunnel at the elbow joint. Although CuTS is typically diagnosed clinically and with electrodiagnostic studies, the importance of imaging in evaluating the condition is growing. Knowing the typical imaging findings of ulnar nerve entrapment is necessary for precise diagnosis and proper treatment. In this article, we focus on the clinical features, workup and complex imaging of the "anatomic" cubital tunnel and relevant pathological entities.

Ulnar neuropathy

Ulnar neuropathy at the elbow is the second most common compressive neuropathy. Less common, although similarly disabling, are ulnar neuropathies above the elbow, at the forearm, and the wrist, which can present with different combinations of intrinsic hand muscle weakness and sensory loss. Electrodiagnostic studies are moderately sensitive in diagnosing ulnar neuropathy, although their ability to localize the site of nerve injury is often limited. Nerve imaging with ultrasound can provide greater localization of ulnar injury and identification of specific anatomical pathology causing nerve entrapment. Specifically, imaging can now reliably distinguish ulnar nerve entrapment under the humero-ulnar arcade (cubital tunnel) from nerve injury at the retro-epicondylar groove. Both these pathologies have historically been diagnosed as either "ulnar neuropathy at the elbow," which is non-specific, or "cubital tunnel syndrome," which is often erroneous. Natural history studies are few and limited, although many cases of mild-moderate ulnar neuropathy at the elbow appear to remit spontaneously. Conservative management, perineural steroid injections, and surgical release have all been studied in treating ulnar neuropathy at the elbow. Despite this, questions remain about the most appropriate management for many patients, which is reflected in the absence of management guidelines.

"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.

Imaging of Anatomical Variants Around the Elbow

The elbow is a synovial joint able to perform flexion, extension, supination, and pronation. Knowledge of anatomical variants is crucial to avoid misinterpretation during the evaluation of the elbow joint. We address those anatomical variants simulating pathologic conditions.

Radial nerve compression: anatomical perspective and clinical consequences

The radial nerve is the biggest branch of the posterior cord of the brachial plexus and one of its five terminal branches. Entrapment of the radial nerve at the elbow is the third most common compressive neuropathy of the upper limb after carpal tunnel and cubital tunnel syndromes. Because the incidence is relatively low and many agents can compress it along its whole course, entrapment of the radial nerve or its branches can pose a considerable clinical challenge. Several of these agents are related to normal or variant anatomy. The most common of the compressive neuropathies related to the radial nerve is the posterior interosseus nerve syndrome. Appropriate treatment requires familiarity with the anatomical traits influencing the presenting symptoms and the related prognoses. The aim of this study is to describe the compressive neuropathies of the radial nerve, emphasizing the anatomical perspective and highlighting the traps awaiting physicians evaluating these entrapments.

The prevalence of the anatomical variation in a Turkish population: supernumerary muscle-anconeus epitrochlearis

INTRODUCTION

The anconeus epitrochlearis (AE) muscle is an accessory muscle located between the medial cortex of the olecranon and the inferior surface of the medial epicondyle, posterior to the ulnar nerve. This muscle may compress the ulnar nerve causing a clinical neuropathy. We aimed to determine the gender and side characteristics of the AE muscle in patients who underwent elbow magnetic resonance imaging (MRI) and report its prevalence in a Turkish population.

MATERIALS AND METHODS

A total of 209 patients (210 elbows) who underwent elbow MRI between January and December 2020 were retrospectively evaluated. Cases with the AE muscle were included in the study. The craniocaudal (CC) dimension was examined from the coronal section, and the transverse (TR) and anteroposterior (AP) dimensions from the axial sections. Statistical analyses were performed to determine the relationship between the presence of the AE muscle and age, gender, and side (right/left). Differences between sexes and sides in terms of muscle sizes were evaluated using statistical tests.

RESULTS

The AE muscle was detected in 17 patients (18 elbows) (8.1%). The mean age of the patients was 41.52 ± 14.63 years. There was no statistically significant difference between the male and female patients in terms of age. This accessory muscle was found in nine female (9.8%) and eight male (6.3%) patients in total. There was one (0.5%) patient with the bilateral AE muscle, who was female. The accessory muscle was located in the right elbow in 13 patients (10.71%), and left elbow in five (4.10%). It was more common in the right elbow in both genders. The muscle was larger in the male patients and the right elbow, but this was not statistically significant.

CONCLUSION

The prevalence of the AE muscle was determined to be 8.1% in a Turkish population, and this muscle was more common among the women and in the right elbow.

Ultrasound in the Differential Diagnosis of Medial Epicondylalgia and Medial Elbow Pain-Imaging Findings and Narrative Literature Review

Medial epicondylalgia (ME), commonly known as “the golfer’s elbow”, typically develops in individuals who perform repetitive forearm movements and weight-bearing activities. It accounts for up to 20% of all epicondylitis cases and is most prevalent in particular sports and occupations. Though the diagnosis can be made based on sole clinical examination, additional imaging might be essential for confirmation of medial epicondylitis and excluding other pathologies of the medial epicondyle region. US imaging, with a sensitivity and specificity of 95% and 92%, respectively, remains a practical and accessible alternative to MRI. However, its diagnostic efficacy highly depends on the operator’s experience and requires proper technique. This article describes the ultrasound examination and technique for adequate visualization of elbow joint structures. It also discusses the differential diagnosis of other common and less-known pathologies of the medial compartment of the elbow, including snapping triceps, medial collateral ligament injury, and cubital tunnel neuropathy.

Diagnosing ulnar neuropathy at the elbow on MRI: importance of the longitudinal extent of the hyperintense ulnar nerve

OBJECTIVE

To evaluate the usefulness of the longitudinal extent (LE) of high ulnar nerve signal intensity (SI) for the diagnosis of ulnar neuropathy at the elbow (UNE).

MATERIALS AND METHODS

This retrospective study included 68 patients who underwent elbow MRI. Twenty-seven and 41 patients were enrolled in the UNE and control groups, respectively. Qualitative and quantitative analyses of the SI and size of the ulnar nerve at the cubital tunnel, proximal, and distal to the cubital tunnel were performed. Cross-sectional area (CSA) and nerve-to-muscle contrast ratio (NMCR) were measured at each level. The LE of the hyperintense ulnar nerve was evaluated using axial and coronal images. The presence of space-occupying lesions (SOLs), subluxation, and muscle denervation were recorded. Univariate and multivariate analyses were performed to identify independent predictive factors.

RESULTS

Ulnar nerve hyperintensity at and distal to the cubital tunnel, presence of compression, SOL, muscle denervation, LE of hyperintense ulnar nerve, NMCR, and CSA at and distal to the cubital tunnel significantly differed between the two groups. Multivariate logistic regression analysis showed that the LE of the hyperintense ulnar nerve and CSA at the cubital tunnel were independent predictive factors for UNE (p < 0.05).

CONCLUSION

LE of the hyperintense ulnar nerve could be a useful predictive factor for UNE.

Imaging of Nerve Disorders in the Elbow

Neuropathies of the elbow represent a spectrum of disorders that involve more frequently the ulnar, radial, and median nerves. Reported multiple pathogenic factors include mechanical compression, trauma, inflammatory conditions, infections, as well as tumor-like and neoplastic processes. A thorough understanding of the anatomy of these peripheral nerves is crucial because clinical symptoms and imaging findings depend on which components of the affected nerve are involved. Correlating clinical history with the imaging manifestations of these disorders requires familiarity across all diagnostic modalities. This understanding allows for a targeted imaging work-up that can lead to a prompt and accurate diagnosis.

Diagnosis of ulnar nerve entrapment anterior to the medial epicondyle by ultrasound elastography and diffusion tensor imaging with fiber tractography: a case report

Ulnar/cubital tunnel syndrome is the second most common compressive neuropathy of the upper limb. Permanent location of the ulnar nerve anterior to the medial epicondyle is extremely rare, with only five cases reported in the literature. Using ultrasound elastography and diffusion tensor imaging with fiber tractography, we diagnosed a case in which ulnar nerve entrapment was associated with anterior nerve location. Surgical release confirmed the diagnosis and the patient was symptom free 3 months after surgery.

Role of diffusion tensor imaging in the evaluation of ulnar nerve involvement in leprosy

OBJECTIVE

Early detection of peripheral neuropathy is extremely important as leprosy is one of the treatable causes of peripheral neuropathy. The study was undertaken to assess the role of diffusion tensor imaging (DTI) in ulnar neuropathy in leprosy patients.

METHODS

This was a case-control study including 38 patients (72 nerves) and 5 controls (10 nerves) done between January 2017 and June 2019. Skin biopsy proven cases of leprosy, having symptoms of ulnar neuropathy (proven on nerve conduction study) were included. MRI was performed on a 3 T MR system. Mean cross-sectional area, fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of ulnar nerve at cubital tunnel were calculated. Additional ancillary findings and appearance of base sequences were evaluated.

RESULTS

Ulnar nerve showed thickening with altered T₂W signal in all the affected nerves, having an average cross-sectional area of 0.26 cm². Low FA with mean of 0.397 ± 0.19 and high ADC with mean of 1.28 ± 0.427 x 10 ^-3 mm²/s of ulnar nerve in retrocondylar groove was obtained. In the control group, mean cross-sectional area was 0.71cm² with mean FA and ADC of 0.53 ± 0.088 and 1.03 ± 0.24 x 10 ^-3 mm²/s respectively. Statistically no significant difference was seen in diseased and control group. Cut-off to detect neuropathy for FA and ADC is 0.4835 and 1.1020 × 10 ^-3 mm²/s respectively.

CONCLUSION

DTI though is challenging in peripheral nerves, however, is proving to be a powerful complementary tool for assessment of peripheral neuropathy. Our study validates its utility in infective neuropathies.

ADVANCES IN KNOWLEDGE

1. DTI is a potential complementary tool for detection of peripheral neuropathies and can be incorporated in standard MR neurography protocol.2. In leprosy-related ulnar neuropathy, altered signal intensity with thickening or abscess of the nerve is appreciated along with locoregional nodes and secondary denervation changes along with reduction of FA and rise in ADC value.3. Best cut-offs obtained in our study for FA and ADC are 0.4835 and 1.1020 × 10 ^-3 mm²/s respectively.

How to Report: Elbow MRI

The elbow is the least common of the main joints examined with magnetic resonance imaging (MRI), thus radiologists may be less familiar with writing these reports. This article addresses the main pathologies encountered in and around the elbow, emphasizing the specific features that need reporting and providing examples of terminology to use when describing these abnormalities.

MRI of the Elbow: How to Do It

The diagnostic cascade for elbow complaints starts with the physical examination and radiographs that already can clarify or rule out many causes. Depending on the suspected pathology, additional imaging is necessary. Magnetic resonance imaging (MRI) has the advantage of accurately demonstrating a broad spectrum of diseases. The main indication for noncontrast MRI of the elbow is chronic epicondylitis. For magnetic resonance (MR) arthrography, it is suspected chondral and osteochondral abnormalities. Indirect MR arthrography is an option when direct arthrography is not practicable. MR arthrography of the elbow with traction is feasible, with promising results for the assessment of the radiocapitellar cartilage.

Elbow Instability

The stability of the elbow is based on a combination of primary (static) and secondary stabilizers (dynamic). In varus stress, the bony structures and the lateral ulnar collateral ligament (LUCL) are the primary stabilizers, and in valgus stress, the ulnar collateral ligament (UCL) is the primary stabilizer. The flexor and extensor tendons crossing the elbow joint act as secondary stabilizers. Elbow instability is commonly divided into acute traumatic and chronic instability. Instability of the elbow is a continuum, with complete dislocation as its most severe form.Posterolateral rotatory instability is the most common elbow instability and can be detected at imaging both in the acute as well as the chronic phase. Imaging of suspected elbow instability starts with radiographs. Depending on the type of injury suspected, it is followed by magnetic resonance imaging (MRI) or computed tomography evaluation for depiction of a range of soft tissue and osseous injures. The most common soft tissue injuries are tears of the LUCL and the radial collateral ligament; the most common osseous injuries are an osseous LUCL avulsion, a fracture of the coronoid process, and a radial head fracture.Valgus instability is the second most common instability and mostly detected in the chronic phase, with valgus extension overload the dominant pattern of injury. The anterior part of the UCL is insufficient in valgus extension overload due to repetitive medial tension seen in many overhead throwing sports, with UCL damage readily seen at MRI.

Elbow Imaging: Variants and Asymptomatic Findings

One of the key principles in the interpretation of radiology images is the ability to differentiate between normal and abnormal findings. This article provides a comprehensive overview of normal structures and anatomical variants occurring around the elbow including potential diagnostic pitfalls. We discuss frequently observed anatomical variants found in routine clinical practice associated with osseous, ligamentous, musculotendinous, and neurovascular structures at the elbow that may simulate pathology or predispose to symptoms under specific circumstances.

Magnetic Resonance Neurography: Improved Diagnosis of Peripheral Neuropathies

Peripheral neuropathies account for the most frequent disorders seen by neurologists, and causes are manifold. The traditional diagnostic gold-standard consists of clinical neurologic examinations supplemented by nerve conduction studies. Due to well-known limitations of standard diagnostics and atypical clinical presentations, establishing the correct diagnosis can be challenging but is critical for appropriate therapies. Magnetic resonance neurography (MRN) is a relatively novel technique that was developed for the high-resolution imaging of the peripheral nervous system. In focal neuropathies, whether traumatic or due to nerve entrapment, MRN has improved the diagnostic accuracy by directly visualizing underlying nerve lesions and providing information on the exact lesion localization, extension, and spatial distribution, thereby assisting surgical planning. Notably, the differentiation between distally located, complete cross-sectional nerve lesions, and more proximally located lesions involving only certain fascicles within a nerve can hold difficulties that MRN can overcome, when basic technical requirements to achieve sufficient spatial resolution are implemented. Typical MRN-specific pitfalls are essential to understand in order to prevent overdiagnosing neuropathies. Heavily T2-weighted sequences with fat saturation are the most established sequences for MRN. Newer techniques, such as T2-relaxometry, magnetization transfer contrast imaging, and diffusion tensor imaging, allow the quantification of nerve lesions and have become increasingly important, especially when evaluating diffuse, non-focal neuropathies. Innovative studies in hereditary, metabolic or inflammatory polyneuropathies, and motor neuron diseases have contributed to a better understanding of the underlying pathomechanism. New imaging biomarkers might be used for an earlier diagnosis and monitoring of structural nerve injury under causative treatments in the future.

Imaging of Elbow Injuries

Familiarity with throwing mechanics during elbow range of motion allows accurate diagnosis of sports-related elbow injuries, which occur in predictable patterns. In addition, repetitive stress-related injuries are often clinically apparent; however, imaging plays an important role in determining severity as well as associated injuries that may affect clinical management. A detailed understanding of elbow imaging regarding anatomy and mechanism of injury results in prompt and precise treatment.

The ultrasonographic assessment of the morphologic changes in the ulnar nerve at the cubital tunnel in Japanese volunteers: relationship between dynamic ulnar nerve instability and clinical symptoms

Background

We investigated the differences in the prevalence of ulnar nerve instability (UNI) by hand dominance and evaluated the relationship between UNI and morphologic changes in the ulnar nerve and the clinical findings and upper limb function.

Methods

This study examined 153 healthy participants (n = 306 elbows; 44 men, 112 women; mean age 65.4 years) who underwent ultrasonography to assess the ulnar nerve cross-sectional area (UNCSA) at three points of the bilateral cubital tunnel at 30° of elbow flexion. Participants were divided into three groups based on the ultrasonography findings of UNI: no instability (type N), subluxation (type S), and dislocation (type D). For the dominant and nondominant sides, we assessed the relationship between the UNCSA and clinical factors, including the age, gender, height, weight, body mass index, fat mass, grip strength, key pinch strength, UNCSA, and Patient-Rated Elbow Evaluation score.

Results

We identified 75 cases without instability in both elbows and 78 cases with some instability. The prevalence of UNI was 51%. No significant difference was found between hand dominance and the prevalence of UNI. The UNCSA at 1 cm proximal to the medial epicondyle on the bilateral sides in type S was the most increased among three types.

Conclusion

UNI was identified in almost half of the participants, with no marked difference found in the hand dominance. The UNCSA at 1 cm proximal to the medial epicondyle was significantly increased the most in type S. UNI does not appear to be associated with elbow symptoms in the general population.

Determination of optimum pixel size and slice thickness for tractography and ulnar nerve diffusion tensor imaging at the cubital tunnel using 3T MRI

BACKGROUND

Small peripheral nerve tractography is challenging because of the trade-off among resolution, image acquisition time, and signal-to-noise ratio.

PURPOSE

To optimize pixel size and slice thickness parameters for fiber tractography and diffusion tensor imaging (DTI) of the ulnar nerve at the cubital tunnel using 3T magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Fifteen healthy volunteers (mean age 30 ± 6.8 years) were recruited prospectively. Axial T2-weighted and DTI scans were acquired, covering the cubital tunnel, using different pixel sizes and slice thicknesses. Three-dimensional (3D) nerve tractography was evaluated for the median number and length of the reconstructed fiber tracts and visual score from 0 to 5. Two-dimensional (2D) cross-sectional DTI was evaluated for fractional anisotropy (FA) values throughout the length of the ulnar nerve.

RESULTS

A pixel size of 1.3 mm² revealed the highest number of reconstructed nerve fibers compared to that of 1.1 mm² (P = 0.048), with a good visual score. A slice thickness of 4 mm had the highest number of reconstructed nerve fibers and visual score compared with other thicknesses (all P < 0.05). In 2D cross-sectional images, the median FA values were in the range of 0.40-0.63 at the proximal, central, and distal portions of the cubital tunnel. Inter-observer agreement for all parameters was good to excellent.

CONCLUSION

For fiber tractography and DTI of the ulnar nerve at the cubital tunnel, optimal image quality was obtained using a 1.3-mm² pixel size and 4-mm slice thickness under MR parameters of this study at 3T.

Ulnar Nerve Dislocation and Subluxation from the Cubital Tunnel Are Common in College Athletes

Background: Hypermobility of the ulnar nerve from the cubital tunnel reportedly occurs in healthy people without symptoms of ulnar neuropathy. However, the occurrence rate in athletes is unknown. We examined the occurrence rate of ulnar nerve hypermobility using ultrasonography, symptoms, and physical findings in athletes and compared the results of four types of sports. Methods: Medical charts of college athletes competing in baseball, rugby, soccer, and long-distance running between March and November 2018 were retrospectively examined. Dynamic evaluation of the ulnar nerve was performed using ultrasonography and categorized as Types N, S, and D respectively, indicating normal position, subluxation, and dislocation. Subjective and objective findings were evaluated. Results: The present study included 246 male athletes (mean age, 19.7 years; 492 elbows) including 46% Type D, 29.8% Type S, and 24.2% Type N. Subjective findings showed pain and dysesthesia in 9% and 4.5% of participants, respectively, whereas objective findings showed Tinel sign in 6%, nerve tension test in 1.3%, Froment’s sign in 0.5%, and weakness of strength of opponens digiti minimi muscle in 8% of patients with Types D and S. Conclusions: There was a high-frequency hypermobility of the ulnar nerve from the cubital tunnel with or without subjective and objective findings in college athletes.

Nerve entrapment around elbow

Entrapment neuropathy around elbow is a common cause of disability across all age groups. The major nerves that traverse the elbow are ulnar, median and radial nerves and their branches. Cubital tunnel syndrome leading to ulnar nerve compression can often present with significant pain, paresthesia or weakness. Median and Radial nerve compression around the elbow, albeit less frequent, can also lead to significant morbidity and must be kept in the differential diagnosis when dealing with patients complaining of persistent pain around the elbow and weakness of forearm/hand muscles. Electrodiagnostic studies can be a useful adjunct to clinical examination, to help localize the site and quantify the grade of compression. Management should involve a trial of conservative treatment and failing that, surgical treatment should be considered. We hereby provide an overview of nerve entrapments around the elbow including their applied anatomy, etiology, clinical assessment and overview of the current concepts in surgical treatment.

Comparison of electrodiagnosis, neurosonography and MR neurography in localization of ulnar neuropathy at the elbow

INTRODUCTION

In patients with ulnar neuropathy at the elbow (UNE) the precise determination of the site of lesion is important for subsequent differential diagnostic considerations and therapeutic management. Due to a paucity of comparable data, to better define the role of different diagnostic tests, we performed the first prospective study comparing the diagnostic accuracy of short segment nerve stimulation, nerve ultrasonography, MR neurography (MRN), and diffusion tensor imaging (DTI) in patients with UNE.

METHODS

UNE was clinically diagnosed in 17 patients with 18 affected elbows. For all 18 affected elbows in patients and 20 elbows in 10 healthy volunteers, measurements of all different diagnostic tests were performed at six anatomical positions across the elbow with measuring points from distal (D4) to proximal (P6) in relation to the medial epicondyle (P0). Additional qualitative assessment regarding structural changes of surrounding nerve anatomy was conducted.

RESULTS

The difference between affected arms of patients and healthy control arms were most frequently the largest at measure intervals D2 to P0 and P0 to P2 for electrophysiological testing, or measure points P0 and P2 for all other devices, respectively. At both levels P0 and at P2, T2 contrast-to-noise ratio (CNR) of MRN and mean diffusivity (MD) of DTI-based MRN showed best accuracies.

DISCUSSION

This study revealed differences in diagnostic performance of tests concerning a specific location of UNE, with better results for T2 contrast to noise ratio (CNR) in MRN and mean diffusivity of DTI-based MRN. Additional testing with MRN and nerve ultrasonography is recommended to uncover anatomical changes.

[Imaging of the hand : What should be considered regarding the nerves?]

BACKGROUND

Peripheral nerve disorders of the hand and wrist are most commonly caused by entrapment neuropathies, while traumatic nerve injuries and neoplasms are less common.

OBJECTIVES

The indication for additional imaging methods and different imaging options, especially in patients with atypical symptoms or remaining unclear etiology of symptoms after completion of standard diagnostics, are presented.

MATERIALS AND METHODS

The imaging methods magnetic resonance (MR) neurography and neurosonography are introduced, and typical findings as well as diagnostic pitfalls are presented.

RESULTS

The diagnostic gold standard, which comprises a past medical history, neurologic examination and electrophysiology, can often establish the diagnosis. Imaging methods, especially MR neurography and neurosonography, are gaining increasing importance in the diagnostic workup of atypical neuropathies, as well as in the determination of the exact lesion location and spatial lesion extension, especially for surgical planning. Recent technical advances allow high-resolution depiction of small distal terminal nerve branches.

CONCLUSIONS

MR neurography allows for the high-resolution depiction of peripheral nerves of the hand and wrist. It can confirm the diagnosis of neuropathy, identify the exact lesion location, and rule out any differential diagnoses. Neurosonography is a time- and cost-efficient alternative diagnostic method.

MRI of the ulnar nerve pre- and post-transposition: imaging features and rater agreement

OBJECTIVE

Determine the rater agreement of MRI features of the ulnar nerve pre- and post-transposition and association with recurrent symptoms.

MATERIALS AND METHODS

This IRB-approved retrospective cohort analysis examined 23 subjects who underwent elbow MRI pre- and post-ulnar nerve transposition from 1999 to 2018, 10 of whom developed recurrent symptoms. Pre- and post-transposition MRIs were evaluated by two blinded radiologists for ulnar nerve cross-sectional area, signal intensity, fascicular architecture, caliber change, and perineural scar. Inter-rater agreement was estimated using intraclass correlation coefficients (ICCs) for continuous variables and Gwet's agreement coefficient (AC) for categorical variables. Binary logistic regression modeling probed associations between imaging markers and symptom recurrence.

RESULTS

The ulnar nerve, post-operatively, demonstrated statistically significant increases in size (p < 0.001), signal intensity (p = 0.021), and abrupt caliber change (p = 0.024). None of the imaging features, except for higher signal intensity of the nerve pre-transposition as demonstrated by one rater, were predictive of symptom recurrence. Inter-rater agreement for cross-sectional area measurements of the ulnar nerve at the cubital tunnel was excellent (ICCs of 0.91 and 0.83). Substantial-to-excellent inter-rater agreement was observed pre-operatively for nerve signal intensity, caliber change, and fascicular architecture. Post-operatively, agreement on nerve signal intensity and perineural scar was excellent (ACs of 0.90 and 0.88), but only slight for caliber change (0.15).

CONCLUSION

Inter-rater agreement for qualitative and quantitative assessment of the ulnar nerve was generally robust. Post-transposition, the ulnar nerve was generally larger and more T2-hyperintense, but MRI features were not predictive of recurrent ulnar neuropathy, except for perhaps the signal intensity of the nerve pre-transposition.

The prevalence of anconeus epitrochlearis muscle and Osborne's ligament in cubital tunnel syndrome patients and healthy individuals: An anatomical study with meta-analysis

BACKGROUND

Anconeus epitrochlaeris muscle and Osborne's ligament are anatomical variants that are occasionally found at the cubital tunnel of the elbow. In certain individuals, these two structures may compress the ulnar nerve resulting in a cubital tunnel syndrome. Although these variants have been reported extensively, its prevalence is still unclear and its contribution to cubital tunnel syndrome is debatable. The aim of this study is to generate weighted frequency values of the anconeus epitrochlearis and Osborne's ligament, as well as to identify any association of these two structures with gender, side, ethnicity and the development of cubital tunnel syndrome.

METHODS

An anatomical study and a meta-analysis were performed to more accurately study the prevalence of anconeus epitrochlearis and Osborne's ligament. A total of 40 original studies including the present study met the inclusion criteria for meta-analysis and 6 case reports for descriptive analysis.

RESULTS

Crude pooled prevalence estimate of the anconeus epitrochlearis was significantly higher (p < 0.001) in healthy subjects (14.2%) than in subjects diagnosed with cubital tunnel syndrome (4.5%). No significant difference was found for gender, side or laterality. The anconeus epitrochlearis was significantly more common in Europeans populations (18.2%) when compared with North American (6.8%) (p = 0.012) and Asian populations (7.5%) (p < 0.001). Anconeus epitrochlearis had a tendency to be hypertrophied when associated with cubital tunnel syndrome. The definition of Osborne's ligament is unclear, resulting in inconsistent reported prevalence across studies.

CONCLUSION

The present study provides a more accurate estimate of anconeus epitrochlearis across the populations. There was a negative correlation between the presence of anconeus epitrochlearis and the development cubital tunnel syndrome, supporting the idea that the muscle may be protective against cubital tunnel syndrome. Future studies are needed to give proper definition of Osborne's ligament and accurately study its prevalence across populations.

Routine knee MRI: how common are peripheral nerve abnormalities, and why does it matter?

OBJECTIVE

To evaluate the frequency, MRI appearance, and clinical significance of peripheral nerve abnormalities encountered on routine knee MRI.

MATERIALS AND METHODS

A retrospective review was performed to identify consecutive patients who underwent routine knee MRI from March 2015-2018 and had peripheral nerve abnormalities. MRIs were reviewed for the presence of tibial (TN) and common peroneal nerve (CPN) abnormalities (including hyperintensity, bulbous enlargement, discontinuity, architectural distortion, skeletal muscle denervation). The presence or absence of concomitant meniscal, cruciate, and collateral ligament tears was documented. Patient demographics and clinical outcomes were recorded. Descriptive statistics were reported.

RESULTS

The search yielded 8125 MRIs, of which 50 knee MRIs (patient age (years): 44 + 19) had peripheral nerve abnormalities (hyperintensity (TN: 30%(15/50), CPN: 80%(40/50)), bulbous enlargement (TN: 10%(5/50), CPN: 30%(15/50)), discontinuity (TN: 0, CPN: 4%(2/50)), architectural distortion (TN: 4%(2/50), CPN: 18%(9/50)), and skeletal muscle denervation (TN: 14%(7/50), CPN: 28%(14/50)). Medial meniscus (TN: 12% (6/50), CPN: 36%(18/50)), ACL (TN: 4%(2/50), CPN: 32%(16/50)), PCL (TN: 2%(1/50), CPN: 20%(10/50)), and lateral meniscus (TN: 12%(6/50), CPN: 24%(12/50)) tears were frequently present. Of these, 32% (16/50) were treated for peripheral nerve injury (PNI), characterized as high-grade (n = 7/16) or low-grade (n = 9/16). Nerve discontinuity, architectural distortion, and denervation were encountered more in high-grade PNI than low-grade PNI. Five patients were recalled for follow-up imaging and operative management was performed in 36% of cases (18/50).

CONCLUSION

Although uncommon (frequency = 0.6%), peripheral nerve abnormalities (CPN more common than TN) are encountered on routine knee MRI and affect patient management, with 36% requiring surgical treatment.

Advances in imaging technologies for the assessment of peripheral neuropathies in rheumatoid arthritis

Peripheral neuropathy in patients with rheumatoid arthritis is associated with a maladaptive autoimmune response that may cause chronic pain and disability. Nerve conduction studies are the routine method performed when rheumatologists presume its presence. However, this approach is invasive, may not reveal subtle malfunctions in the early stages of the disease, and does not expose abnormalities in structures surrounding the nerves and muscles, limiting the possibility of a timely diagnosis. This work aims to present a narrative review of new technologies for the clinical assessment of peripheral neuropathy in Rheumatoid Arthritis. Through a bibliographic search carried out in five repositories, from 1990 to 2020, we identified three technologies that could detect peripheral nerve lesions and perform quantitative evaluations: (1) magnetic resonance neurography, (2) functional magnetic resonance imaging, and (3) high-resolution ultrasonography of peripheral nerves. We found these tools can overcome the main constraints imposed by the previous electrophysiologic methods, enabling early diagnosis.

Use of Magnetic Resonance Imaging for Orthopedic Trauma and Infection in the Emergency Department

Conditions affecting the musculoskeletal system constitute a significant portion of medical emergencies in the United States, with traumatic injury and infection being two of the most common etiologies. Although physical examination and plain radiographs are often sufficient to guide diagnosis and treatment, there are myriad traumatic and infectious pathologies that are commonly missed or simply not detectable on plain radiographs. Advanced imaging is subsequently warranted for additional workup.Magnetic resonance imaging (MRI) has become an increasingly used imaging modality for musculoskeletal complaints in the emergency department due to its superior visualization of soft tissues, focal edematous changes, and occult osseous insults often not visible on plain radiographs. Although multiple studies have evaluated its utility in the workup of emergency musculoskeletal complaints, there remains a dearth of literature examining the use of MRI for certain occult diagnoses.Radiologists, emergency clinicians, and orthopedic surgeons must be knowledgeable of the indications for MRI in the emergency setting, as delayed diagnosis may contribute to increased morbidity and possibly mortality. This review summarizes the use of MRI in diagnoses relating to trauma or infection among patients presenting to the emergency department with a musculoskeletal complaint.

Clinico-radiological review of peripheral entrapment neuropathies - Part 1 upper limb

PURPOSE

This article aims to review the pertinent anatomy, etiopathogenesis, current clinical and radiological concepts and principles of management in case of upper limb entrapment neuropathies.

METHODS

The review is based on critical analysis of the existing literature as well as our experience in dealing with entrapment neuropathies.

RESULTS

Entrapment neuropathies of the upper limb peripheral nerves are common conditions that are often misdiagnosed because of their varying clinical presentations and lack of standardized diagnostic methods. Clinical assessment and electrodiagnostic studies have been the mainstay; however, imaging techniques have provided newer insights into the pathophysiology of these entities, leading to a paradigm shift in their diagnosis and management. The current best practice protocols for entrapment syndromes are constantly evolving with increasing emphasis on the role high-resolution ultrasound and magnetic resonance imaging. Many imaging criteria are described and we have tried to present the most validated measurements for diagnosing entrapment neuropathies.

CONCLUSION

It is imperative for a clinical radiologist to be familiar with the etiopathogenesis and clinical features of these conditions, in addition to being thorough with the anatomy and the latest imaging strategies.

Magnetic resonance imaging of the elbow

Elbow pain can cause disability, especially in athletes, and is a common clinical complaint for both the general practitioner and the orthopaedic surgeon. Magnetic resonance imaging (MRI) is an excellent tool for the evaluation of joint pathology due to its high sensitivity as a result of high contrast resolution for soft tissues. This article aims to describe the normal imaging anatomy and biomechanics of the elbow, the most commonly used MRI protocols and techniques, and common MRI findings related to tendinopathy, ligamentous and osteochondral injuries, and instability of the elbow.

Ultrasonography of the ulnar nerve in the elbow: video article

Disorders affecting the ulnar nerve in the elbow are common in clinical practice. The diagnosis is based on clinical evaluation and electrodiagnostic tests, but imaging examinations are frequently necessary, particularly for the identification of the structures associated with nerve compression. The purpose of this video article is to review the anatomy, the pathology, scanning techniques, and sonographic appearance of the ulnar nerve in the elbow.

Imaging of Damaged Nerves

Nerve imaging is an important component in the assessment of patients presenting with suspected peripheral nerve pathology. Although magnetic resonance neurography and ultrasound are the most commonly utilized techniques, several promising new modalities are on the horizon. Nerve imaging is useful in localizing the nerve injury, determining the severity, providing prognostic information, helping establish the diagnosis, and helping guide surgical decision making. The focus of this article is imaging of damaged nerves, focusing on nerve injuries and entrapment neuropathies.

[Mononeuropathy of dorsal interosseous nerve: compression by return radial arteries]

Among many causes of compression neuropathies involving the radial nerve, compression of the posterior interosseous nerve (PIN) by the returning radial arteries is rare.

OBJECTIVE

To describe the clinical instrumental characteristics of cases of mononeuropathy caused by compression of the return radial arteries.

MATERIAL AND METHODS

Two observations with neuropathy of the deep branch of the radial nerve, manifested by weakness in the corresponding muscles, inconsistent pain syndrome with previous stereotypic (recurring) physical activity are presented.

RESULTS

According to the results of ultrasound examination of posterior interosseous nerve, a local hypoechogenic increase in the cross-sectional area of nerve of different lengths was revealed. During surgical decompression of the nerve, in the first case, a tight arterial loop was found around the nerve, in the second case, expanded arterial trunks, one of which, of small diameter, covered the nerve in the 'loop', and the other, larger, pierced the nerve. After the operation, regression of motor deficiency and relief of pain were noted.

Prevalence and Clinical Manifestations of the Anconeus Epitrochlearis and Cubital Tunnel Syndrome

Background: The true prevalence of the anconeus epitrochlearis (AE) and the natural history of cubital tunnel syndrome associated with this anomalous muscle are unknown. The purpose of this study was to evaluate the prevalence of AE and to characterize the preoperative and postoperative features of cubital tunnel syndrome caused by compression from an AE. Methods: All elbow magnetic resonance imaging (MRI) scans and all patients undergoing cubital tunnel surgery during a 20-year period were identified and retrospectively reviewed for the presence of an AE. All patients with an AE identified intra-operatively were matched to patients with no AE identified at surgery based on age, sex, concomitant procedures, and year of surgery. Preoperative and postoperative physical exam findings, electrodiagnostic study results, time to improvement, and reoperations were compared between the groups. Results: A total of 199 patients had an elbow MRI, and 27 (13.6%) patients were noted to have an AE present. Average time to improvement after surgical release was 23.0 days for patients with an AE and 33.2 days for patients with no AE. Twenty-seven patients with an AE noted improvement at the first postoperative visit (68%) compared to 15 patients without an AE (33%). No patients with an AE underwent reoperation for recurrent symptoms (0%) compared with four patients (10%) without an AE. Conclusions: The prevalence of AE in our study is 13.6%. These patients experience quicker and more reliable symptom improvement after surgical release than those without the anomalous muscle.

Radiomics of peripheral nerves MRI in mild carpal and cubital tunnel syndrome

OBJECTIVE

To assess the discriminative power of radiomics of peripheral nerves at 1.5T MRI, using common entrapment neuropathies of the upper limb as a model system of focal nerve injury.

MATERIALS AND METHODS

Radiomics was retrospectively done on peripheral nerve fascicles on T1-weighted 1.5T MRI of 40 patients with diagnosis of mild carpal (n = 25) and cubital tunnel (n = 15) syndrome and of 200 controls. Z-score normalization and Mann-Whitney U test were used to compare features of normal and pathological peripheral nerves. Receiver operating characteristic analysis was performed.

RESULTS

A total of n = 104 radiomics features were computed for each patient and control. Significant differences between normal and pathological median and ulnar nerves were found in n = 23/104 features (p < 0.001). According to features classification, n = 5/23 features were shape-based, n = 7/23 were first-order features, n = 11/23 features were classified as gray level run length matrix. Nine of the selected features showed an AUC higher that 0.7: minimum AUC of 0.74 (95% CI 0.61-0.89) for sum variance and maximum AUC of 0.90 (95% CI 0.82-0.99) for zone entropy.

CONCLUSION

Features analysis demonstrated statistically significant differences between normal and pathological nerve. The results suggested that radiomics analysis could assess the median and ulnar nerve inner structure changes due to the loss of the fascicular pattern, intraneural edema, fibrosis or fascicular alterations in mild carpal tunnel and mild cubital tunnel syndromes even when the nerve cross-sectional area does not change.

MR imaging of the postsurgical cubital tunnel: an imaging review of the cubital tunnel, cubital tunnel syndrome, and associated surgical techniques

Ulnar nerve compression at the elbow, specifically the cubital tunnel, is the second most common upper extremity compression neuropathy. Many patients presenting with compression symptoms will subsequently undergo surgical intervention. We review the open surgical treatment of cubital tunnel syndrome and review the expected postoperative imaging appearance of those treatments on magnetic resonance imaging (MR), including: simple or in situ decompression, medial epicondylectomy, and anterior transposition, including subcutaneous, intramuscular, and submuscular variants. We discuss the relevant anatomy of the presurgical cubital tunnel and common sites and causes of ulnar nerve compression at and about the cubital tunnel. The imaging appearance of the preoperative and postoperative ulnar nerve and postoperative complications are reviewed.

Anconeus Epitrochlearis Muscle Associated With Cubital Tunnel Syndrome: A Case Series

Background: Cubital tunnel syndrome is a common compressive neuropathy of the upper extremity. The anconeus epitrochlearis muscle is an unusual but occasional contributor. We review our experience with this anomalous muscle in elbows with cubital tunnel syndrome. Methods: We retrospectively reviewed charts of 13 patients noted to have an anconeus epitrochlearis muscle associated with cubital tunnel syndrome. Results: Ten patients had unilateral ulnar neuropathy supported by nerve conduction studies. Three had bilateral cubital tunnel syndrome symptoms with 1 of those having normal nerve conduction studies for both elbows. Eight elbows were treated with myotomy of the anconeus epitrochlearis muscle and submuscular transposition of the ulnar nerve. The other 8 elbows were treated with myotomy of the anconeus epitrochlearis muscle and in situ decompression of the ulnar nerve only. All but 1 patient had either clinical resolution or improvement of symptoms at follow-up ranging from 2 weeks to 1 year after surgery. The 1 patient who had persistent symptoms had received myotomy and in situ decompression of the ulnar nerve only. Conclusions: An anomalous anconeus epitrochlearis occasionally results in compression of the ulnar nerve but is usually an incidental finding. Its contribution to compression neuropathy can be tested intraoperatively by passively ranging the elbow while observing the change in vector and tension of its muscle fibers over the ulnar nerve. Regardless of findings, we recommend myotomy of the muscle and in situ decompression of the ulnar nerve. Submuscular transposition of the ulnar nerve may be necessary if there is subluxation.

Variations of magnetic resonance imaging findings in asymptomatic elbows

BACKGROUND

Magnetic resonance imaging (MRI) findings in asymptomatic patients have been described for hips, knees, ankles, shoulders, and intervertebral disks. No such description exists for the elbow.

METHODS

MRI scans of 189 asymptomatic elbows divided into 3 groups by age (group 1, 20-39 years; group 2, 40-59 years; and group 3, ≥60 years) were evaluated for abnormalities within 13 anatomic structures using a novel classification system.

RESULTS

At least 1 variation was found in all elbows. Of the 13 structures, 8 showed an increase in the prevalence and intensity of signal changes with aging, 2 remained the same, and 2 showed a decrease. One anatomic structure showed no variations in any elbow.

CONCLUSIONS

Elbow MRI variations may be seen regardless of symptoms. These changes appear to increase in prevalence and intensity with age. Results from this study can be used to help guide the clinician in interpreting MRI findings of the elbow. We hope this study helps provide a contextual background for discussing MRI findings with patients and differentiating age-related variations from true pathology.

MR Imaging of the Upper Limb: Pitfalls, Tricks, and Tips

MR imaging is the modality of choice to evaluate musculoskeletal pathologies of the upper limb in most settings. However, due to the complexity in anatomy, MR imaging can give a false pathologic appearance and lead to several errors in the interpretation of MR imaging findings. Also, several artifacts can be confused with pathologic entities. This article reviews the most frequently encountered conditions in shoulder, elbow, and wrist MR imaging that can represent diagnostic pitfalls mimicking true pathology, together with some possible tips and tricks that can be useful to solve these equivocal cases and achieve a correct diagnosis.

Use of collision tests to identify physiological differences between the median and ulnar nerves

INTRODUCTION

Median and ulnar nerves are used in comparative electrophysiological studies. We analyzed the conduction values in these hand nerves in healthy volunteers to find any physiological differences between them.

METHODS

We performed standard conduction studies and conduction velocity distribution (CVD) tests with estimation of 3 quartiles in 31 healthy right-handed volunteers (17 women, 14 men) with a mean age of 44.8 ± 15.5 years.

RESULTS

The conduction velocities in all quartiles of CVD tests were statistically faster in the ulnar nerve (P < 0.00001), with no differences in the spread of conduction values and no differences between sides. In the ulnar nerve, CVD velocities in all quartiles were faster in the female group (P < 0.05).

DISCUSSION

The ulnar nerve has more fibers conducting with high velocities than does the median nerve. Electrophysiological comparisons between hand nerves must be performed carefully. Muscle Nerve 59:470-474, 2019.

A panorama of radial nerve pathologies- an imaging diagnosis: a step ahead

Abstract

The radial nerve has a long and tortuous course in the upper limb. Injury to the nerve can occur due to a multitude of causes at many potential sites along its course. The most common site of involvement is in the proximal forearm affecting the posterior interosseous branch while the main branch of the radial nerve is injured in fractures of the humeral shaft. Signs and symptoms of radial neuropathy depend upon the site of injury. Injury to the nerve distal to innervation of triceps brachii results in loss of extensor function with sparing of function of the triceps resulting in the characteristic ‘wrist drop’. Injury in the mid-arm is associated with loss of sensation in the dorsolateral aspect of the hand, the dorsal aspect of the radial three-and-a-half digits and in the first web space. Involvement of only the posterior interosseous nerve (PIN) results in weakness of the wrist and digit extensors. Diagnosis relies on clinical examination, electrodiagnostic studies and imaging findings. Plain radiographs are used to identify fracture sites, callus or tumours as cause of compression. Technological advances in ultrasonography have allowed direct visualisation of the involved nerve with assessment of the exact site, extent and type of injury. It yields unmatched information about anatomical details of the nerve. MR imaging adds to soft-tissue details and helps in characterising the lesion. This pictorial review aims to illustrate a wide spectrum of causes of radial neuropathy and emphasises the importance of imaging modalities in diagnosis of neuropathies.

Teaching Points

• Radial nerve injuries are assessed by clinical examination and diagnosed using electrodiagnostic and imaging studies.

• Knowledge of anatomical relations and course of the nerve is necessary to identify the nerve at pre-determined anatomical locations.

• Altered echogenicity and signal intensity, discontinuity of the nerve, focal thickening and cause of compression can be assessed by imaging modalities.

• MR imaging helps in confirmation of the ultrasound findings, differentiating similar appearing lesions and provides additional soft-tissue details.

Comparison of simultaneous multi-slice readout-segmented EPI and conventional single-shot EPI for diffusion tensor imaging of the ulnar nerve

Purpose

To compare conventional single-shot echo planar imaging (ss-EPI) and simultaneous multi-slice (SMS) readout-segmented EPI (rs-EPI) for magnetic resonance diffusion tensor imaging (DTI) of the ulnar nerve.

Materials and methods

This study was approved by the local ethics committee. Ten healthy volunteers (mean age 30.4 ± 4.01 years; range 25–36 years) underwent 3T DTI of the ulnar nerve at the level of the cubital tunnel. DTI was performed based on ss-EPI as well as SMS rs-EPI sequences. Signal-to-noise ratio (SNR), image quality, and DTI parameters in the ulnar nerve (fractional anisotropy, FA; mean diffusivity, MD) were compared between the two sequences by two independent radiologists.

Results

Acquisition time was 5:12 min for ss-EPI and 5:18 min for SMS rs-EPI. Between the two sequences, no significant differences were found for derived DTI measures FA (p = 0.11) and MD values (p = 0.93). Compared to conventional ss-EPI, SMS rs-EPI yielded significantly less ghosting artifacts (p = 0.04) but inferior nerve depiction (p = 0.001) and worse overall image quality (p = 0.008).

Conclusion

SMS rs-EPI is not advantageous over ss-EPI in DTI of the ulnar nerve at the level of the cubital tunnel.