Imaging appearance following surgical decompression of the ulnar nerve

Ultrasound of the Ulnar Nerve: A Pictorial Review: Part 2: Pathological Ultrasound Findings

This is the second part of a two-part article in which we focus on the ultrasound (US) appearance of the pathological ulnar nerve (UN) and its main branches. Findings in a wide range of our pathological cases are presented with high-resolution US images obtained with the latest-generation US machines and transducers.

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 at the elbow: associations of pre-operative DTI parameters with clinical outcomes after cubital tunnel decompression

OBJECTIVES

To evaluate whether DTI parameters of the ulnar nerve at the elbow are associated with clinical outcomes in patients receiving cubital tunnel decompression (CTD) surgery for ulnar neuropathy.

METHODS

This retrospective study included 21 patients with cubital tunnel syndrome who received CTD surgery between January 2019 and November 2020. All patients underwent pre-operative elbow MRI, including DTI. Region-of-interest analysis was performed on the ulnar nerve at three levels around the elbow: above (level 1), cubital tunnel (level 2), and below (level 3). Fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were calculated on three sections at each level. Clinical data on symptom improvement in respect to pain and tingling sensation after CTD were recorded. Logistic regression analysis was used to compare DTI parameters of the nerve at three levels and the entire nerve course between patients with and without symptom improvement after CTD.

RESULTS

After CTD, 16 patients showed improvement in symptoms, but five did not. ROC analysis of DTI parameters showed that AUCs of FA, AD, and MD were higher at level 1 than at levels 2 and 3, with FA showing the highest AUC (level 1: FA, 0.7104 [95% CI, 0.5206-0.9002] vs AD, 0.6521 [95% CI, 0.4900-0.8142] vs MD, 0.6153 [95% CI, 0.4187-0.8119]).

CONCLUSION

In patients who underwent CTD surgery for ulnar neuropathy at the elbow, the DTI parameters of FA, AD, and MD above the cubital tunnel level were associated with clinical outcomes, with FA showing the strongest associations.

KEY POINTS

• After CTD surgery for ulnar neuropathy at the elbow, persistent symptoms may be observed, depending on symptom severity. • DTI parameters of the ulnar nerve at the elbow showed differences in their capacity for discriminating between patients with and without symptom improvement following CTD surgery, with this capacity depending on the nerve level at the elbow. • FA, AD, and MD measured above the cubital tunnel on pre-operative DTI may be associated with surgical outcomes, with FA showing the strongest association (AUC at level 1, 0.7104 [95% CI, 0.5206-0.9002]).

Anatomical Study of the Ventral Upper Arm Muscles with a Case Report of the Accessory Coracobrachialis Muscle

Background and Objectives: The muscles in the upper arm are categorized into two groups: ventral muscles, which include the biceps brachii, coracobrachialis, and brachialis, and dorsal muscles comprising the triceps brachii and anconeus. These muscles are positioned in a way that they contribute to movements at the shoulder and elbow joints. Given the importance of the upper arm muscles for various reasons, they need to be well-known by medical professionals. Ventral upper arm muscles exhibit various topographical and morphological variations. Understanding these variations is critical from both anatomical and clinical standpoints. Therefore, our aim was to conduct an anatomical study focusing on these muscles and potentially identify ventral upper arm muscle variations that could contribute to the broader understanding of this area. For this anatomical study, 32 upper limbs obtained from 16 adult cadavers were dissected. Case report: During our anatomical survey, an accessory coracobrachialis muscle in the left upper extremity of one cadaver was discovered. This additional muscle was located anterior to the classical coracobrachialis muscle and measured 162 mm in length. It originated from the distal anterior surface of the coracoid process and was inserted into the middle third of the humeral shaft. The accessory muscle was supplied by the musculocutaneous nerve. No apparent anatomic variations were observed in the other upper arm muscles in any of the cadavers. Conclusions: Gaining insight into the ventral upper arm muscle variations holds vital significance in both anatomy and clinical practice, as they can influence surgical approaches, rehabilitation strategies, and the interpretation of imaging studies. Based on the morphological characteristics of the accessory coracobrachialis muscle discovered in our case, we hypothesize that it could have caused an atypical palpable mass in the medial brachial area, adjacent to the short head of the biceps brachii.

Neuropathy Score Reporting and Data System (NS-RADS): A Practical Review of MRI-Based Peripheral Neuropathy Assessment

The Neuropathy Score Reporting and Data System (NS-RADS) is a newly developed MR imaging-based classification that standardizes reporting and multidisciplinary communication for MR imaging diagnosis and follow-up of peripheral neuropathies. NS-RADS classification has shown to be accurate and reliable across different centers, readers' experience levels, and degrees of peripheral neuropathies, which include nerve injury, entrapment, neoplasm, diffuse neuropathy, post-interventional status, and temporal changes in muscle denervation. This article brings a practical review of NS-RADS classification, representative MR cases, and a step-by-step tutorial on how to approach this staging system. Readers can gain knowledge and apply it in their practice, aiming to standardize the communications between specialties and improve patient management.

Possible Points of Ulnar Nerve Entrapment in the Arm and Forearm: An Ultrasound, Anatomical, and Histological Study

Background: Ulnar nerve entrapment is one of the most common entrapment neuropathies, usually occurring in the cubital tunnel of the elbow and in Guyon’s canal of the wrist. However, it can also occur at other anatomical locations. Purpose: Our aim was to review other possible locations of ulnar nerve entrapment in an ultrasound and anatomical study. Material and Methods: Eleven upper limbs from eight adult corpses were ultrasonographically examined and subsequently dissected in a dissection laboratory. Four specific anatomical points were analysed, and any anatomical variations were documented. Moreover, six samples of the nerve were taken for histological analysis. Results: Distinct anatomical relationships were observed during ultrasound and dissection between the ulnar nerve and the medial intermuscular septum, the triceps aponeurosis, Osborne’s fascia at the elbow, the arcuate ligament of Osborne and the intermuscular aponeurosis between the flexor carpi ulnaris and the flexor digitorum superficialis muscles. A statistical study showed that these locations are potential areas for ulnar nerve compression. In addition, a fourth head of the triceps brachii muscle was found in some specimens. Conclusion: Results demonstrate that ultrasound is a good tool to investigate ulnar nerve entrapment neuropathy and to identify other anatomical points where the nerve can remain compressed.

Posttreatment Changes of the Elbow

Radiologists should be familiar with the typical surgical procedures applied at the elbow and aware of the spectrum of normal and pathologic appearances of posttreatment situations throughout all radiologic modalities. Most important in the case of posttraumatic surgical elbow procedures is correct postoperative elbow joint alignment, appropriate fixation of joint-forming fragments, and proper insertion of screws, plates, and anchor devices that do not conflict with intra-articular or bony structures. To report soft tissue repair procedures correctly, radiologists need to know the broad spectrum of different techniques applied and their appearance on magnetic resonance imaging.

Imaging the intermuscular septum in the context of ulnar neuropathy

Impingement/entrapment of the ulnar nerve by the intermuscular septum at the distal arm is a common cause of recurrent or recalcitrant ulnar neuropathy following ulnar nerve decompression or anterior transposition. Primary entrapment/impingement of the ulnar nerve along the intermuscular septum may also occur. Evaluation with both ultrasound (US) and MRI can identify entrapment of the ulnar nerve at the intermuscular septum, while dynamic assessment with US can also identify dynamic subluxation of the ulnar nerve over the intermuscular septum.

Imaging the Postoperative Elbow

Evaluation of postoperative images of any joint can be a daunting task, and the elbow is no exception. Patients may be imaged with a complication of the repair, or the postoperative changes may be incidentally observed as the patient is imaged for other reasons. We divide the postoperative elbow into soft tissue procedures (covering ligament and tendon repairs, as well as compartmental release and nerve transposition), joint-related procedures (osteochondral lesion treatment, ostectomy, and joint replacement), and bone procedures (fracture fixation). We summarize the procedures and their indications, show normal imaging appearances, and finally cover common complications.

Qualitative and quantitative analysis of 3D T1 Silent imaging

PURPOSE

To compare brain magnetic resonance imaging (MRI) using T1 3D Silent and fast T1 3D Gradient-Echo (GRE) BRAin VOlume (known as BRAVO) sequences. The primary aim is to assess the quantitative and qualitative analysis of Silent and BRAVO images by the measurement of the contrast (C), the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). The second aim is to estimate the subjective sound levels and the specific absorption rate (SAR).

METHODS

Twenty-two subjects had T1 3D Silent and T1 3D BRAVO sequences added to the standard MR examination. The qualitative analysis of the two sequences was performed by two radiologists independently. The quantitative analysis was performed by placing regions of interest on the cerebrospinal fluid, on the white and grey matter. The C, the CNR and the SNR were calculated for each sequence. After each T1-3D sequence, subjects gave a score rating to evaluate the acoustic noise. Finally, the SAR was evaluated by the digital imaging and communications in medicine (DICOM) tags.

RESULTS

The image quality scores obtained by the two radiologists were higher for BRAVO compared to the Silent. However, qualitatively, the Silent images were similar to BRAVO for diagnostic use. Quantitatively, CNR for GM-CSF was comparable in the two sequences and SNR in CSF was higher in Silent than BRAVO. The acoustic noise of Silent sequence was statistically lower compared with BRAVO. The maximum SAR measured was 1.4 W/kg.

CONCLUSIONS

3D T1 Silent can be a valid alternative technique to conventional BRAVO to reduce the acoustic noise preserving the diagnostic accuracy. However, radiologists preferred the conventional sequence to Silent.