case_images: PMC11717166_01
case_images: US (A-C) and MR (D) images of patient's posterior cord of brachial plexus and axillary nerve. The US images were obtained with a 18-5 MHz linear array transducer placed in the axilla and oriented along the long axis of the humeral head (HH) with the patient's arm abducted, elevated, and externally rotated. (A) A swollen and hypoechoic edematous posterior cord (void arrowhead) is noted medial to the posterior circumflex artery (white arrow) and superficial to the subscapularis muscle (Ss). (B) Sweeping the probe more laterally and distally, an enlarged axillary nerve (white arrowheads) is seen lying between the Teres Major muscle (Tm) and, on the floor, the inferior joint capsule (ca); the posterior circumflex artery (white arrows) runs just anterior to the axillary nerve with an oblique course, at the level of humeral surgical neck (HN). (C) By rotating the ultrasound probe of 90 , an irregular thickening of the axillary nerve can be appreciated also in its long axis. (D) Axial proton density fat-sat MR image of the shoulder at the retropectoralis minor space shows the posterior cord (void arrowhead) lateral and posterior to the axillary artery (white asterisk) and anterior to the subscapularis muscle (Ss). Hyperintensity and enlargement of the posterior cord indicate inflammation, leading to axonal myelin sheath disruption and increased intraneural fluid. Note the denervation of muscles supplied by the posterior cord and axillary nerve causing intramuscular edema, seen as increased signal intensity in the deltoid (black asterisk) and subscapularis muscle (Ss) compared to the pectoralis major (pM), pectoralis minor (pm), and infraspinatus muscles (Is). ca, joint capsule; HH, humeral head; HN, humeral surgical neck; Is, infraspinatus; pM, pectoralis major; pm, pectoralis minor; Ss, subscapularis; TM, teres major.
case_images: JCU-53-172-g001.jpg
case_images: PMC11717166_01_JCU-53-172-g001.jpg
case_images: jcu23817-fig-0001
case_images: MHz linear array probe. Mild enlargement of the roots and divisions of the brachial plexus and more obvious enlargement of the axillary nerve with hourglass constrictions along its course posterior to the humeral surgical neck were identified (Figure 1); the same findings were observed along the musculocutaneous nerve, especially at its exit from the two ends of the coracobrachialis muscle and its entrance between the biceps and brachialis muscles (Figure 2). MRI confirmed mild signal hyperintensity in the T2-weighted sequences of the brachial plexus, posterior cord (Figure 1) and musculocutaneous nerve divisions (Figure 2).
case_images: MR (A, C) and US (B, D) images of patient's musculocutaneous nerve. (A) Axial PD fat-sat MR image at the proximal humerus (H) shows a thickened, hyperintense musculocutaneous nerve (white arrowhead) anterior to the axillary artery (white asterisk), just behind the coracobrachialis muscle (cb). The deltoid (D) and long head of the triceps (Tr) muscles appear slightly hyperintense due to denervation related to posterior cord dysfunction. (B) high-resolution 18-5 MHz ultrasound image depicts typical torsion neuropathy features: The musculocutaneous nerve (white arrowheads), seen in its long axis between the two heads of the coracobrachialis muscle (cb1, cb2), appears enlarged and hypoechoic with multifocal narrowings (void arrowheads) indicating torsional constrictions. (C) T2-STIR MR axial image at a more distal level shows a swollen, hyperintense musculocutaneous nerve (white arrowheads) between the brachialis (B) and coracobrachialis muscles (cb). Denervation signs are present in the long and lateral heads of the triceps (Tr, TrL), deltoid (D), biceps brachii, and latissimus dorsi. (D) High-resolution 22-8 MHz ultrasound image in the long axis view shows the musculocutaneous nerve between the biceps brachii (B) and coracobrachialis muscle (cb) with another narrowing point and focal epineurium thickening, resulting in an hourglass-like appearance. Black asterisk, fluid distending the tenosynovial sheath of the long head of the biceps tendon; cb, coracobrachialis; D, deltoid; H, humerus; Ld, latissimus dorsi; Sa, serratus anterior; Tr, long head of the triceps; Tr, long head of the triceps; TrL, lateral head of the triceps; White asterisk, brachial artery.
case_images: JCU-53-172-g005.jpg
case_images: PMC11717166_01_JCU-53-172-g005.jpg
case_images: jcu23817-fig-0002
case_images: MHz linear array probe. Mild enlargement of the roots and divisions of the brachial plexus and more obvious enlargement of the axillary nerve with hourglass constrictions along its course posterior to the humeral surgical neck were identified (Figure 1); the same findings were observed along the musculocutaneous nerve, especially at its exit from the two ends of the coracobrachialis muscle and its entrance between the biceps and brachialis muscles (Figure 2). MRI confirmed mild signal hyperintensity in the T2-weighted sequences of the brachial plexus, posterior cord (Figure 1) and musculocutaneous nerve divisions (Figure 2).
case_images: Transverse HRUS images of the patient's radial nerve in the spiral groove obtained at the 30-day follow-up with a 18-5 MHz linear array probe. (A) Just proximal to a deep stricture, the nerve appears enlarged and inhomogeneous (white arrowheads) with a complete loss of fascicular echotexture, indicating intraneural edema. (B) At the level of the stricture, the nerve is markedly reduced in size (white arrowheads), with the hyperechoic epineurium still visible. (C) More distally, the nerve regains its swollen appearance (white arrowheads), indicative of torsion along its course. (D) The application of SMI, a power-doppler technique sensitive to slow-flow, enables the visualization of hypervascularity in the enlarged radial nerve (white arrow). Br, brachialis; H, humerus; LhT, lateral head of the triceps.
case_images: JCU-53-172-g004.jpg
case_images: PMC11717166_01_JCU-53-172-g004.jpg
case_images: jcu23817-fig-0003
case_images: HRUS examination revealed a massive enlargement of the radial nerve, with a deep constriction at the humeral spiral groove, suggestive of an immunomodulated process; application of superb microvascular imaging (SMI) revealed a focal increase in vascularity in the epinevrium of the enlarged radial nerve, just proximal and distal to the constriction (Figure 3).
case_images: Transverse HRUS images of the medial proximal arm, acquired with a 24-5 MHz linear array transducer on the same plane before (A) and after (B) therapy. In (A), the musculocutaneous nerve (white arrowhead) is seen in short axis entering between the two heads of the coracobrachialis (cb1, cb2). In (B), a slight reduction in the size of the musculocutaneous nerve (white arrowhead) is observed. The change in nerve volume is more evident when compared to the unchanged median nerve (void arrowhead) and proximal radial nerve (white arrow). A, brachial artery; cb, coracobrachialis; H, humerus; Tm, Teres Major.
case_images: JCU-53-172-g002.jpg
case_images: PMC11717166_01_JCU-53-172-g002.jpg
case_images: jcu23817-fig-0004
case_images: MRI and electrodiagnostic studies; only HRUS examination was performed, which revealed a decrease in musculocutaneous nerve size, probably due to reduction of intraneural edema (Figure 4). Morphological alterations in the other nerves involved were unchanged; in particular, the vascular congestion detected with SMI near the constriction along the radial nerve was still present.