Sonographic Pearls for Imaging the Brachial Plexus and Its Pathologies

Abstract

The brachial plexus (BP) is a complicated neural network, which may be affected by trauma, irradiation, neoplasm, infection, and autoimmune inflammatory diseases. Magnetic Resonance Imaging is the preferred diagnostic modality; however, it has the limitations of high cost and lack of portability. High-resolution ultrasound has recently emerged as an unparalleled diagnostic tool for diagnosing postganglionic lesions of the BP. Existing literature describes the technical skills needed for prompt ultrasound imaging and guided injections for the BP. However, it remains particularly challenging for beginners to navigate easily while scanning its different parts. To address this, we share several “clinical pearls” for the sonographic examination of the BP as well as its common pathologies.

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“…The brachial plexus (BP) is located in the thoracic outlet area, identifiable from the lateral portion of the scalene muscle anterior to the lower portion of the pectoralis minor muscle [15]. BP is the neurological structure that allows somatosensory innervation of the upper limb and part of the thoracic outlet [16].…”

“…BP is the neurological structure that allows somatosensory innervation of the upper limb and part of the thoracic outlet [16]. The ventral branches of the spinal nerves from C5 to T1 form BP; it is not uncommon for C4 and T2 roots to converge to immerse themselves in BP [15]. The anterior or ventral branches are the roots found in the neck in the scalene triangle (anterior and middle scalene muscle); the diameter of C5 is the smallest, compared to the volume of C7 and C8, which roots are the largest [15].…”

“…The ventral branches of the spinal nerves from C5 to T1 form BP; it is not uncommon for C4 and T2 roots to converge to immerse themselves in BP [15]. The anterior or ventral branches are the roots found in the neck in the scalene triangle (anterior and middle scalene muscle); the diameter of C5 is the smallest, compared to the volume of C7 and C8, which roots are the largest [15]. The branches will form the upper trunk (C5-C6), the middle trunk (C7), and the lower trunk (C8-T1); the trunks are formed after the scalene triangle near the subclavian artery [17].…”

“…In the proximity of the first rib and the subclavian muscle, the divisions will create three cords. The lateral cord (central position, C5-C7) will come out of the upper and middle trunks; the posterior cord will form from the posterior trunk (cranial position, C5-T1); the lower trunk will form the middle cord (caudal position, C8-T1) [15][16]. In the lateral area of the pectoralis minor muscle and passing under the coracoid process of the scapular bone, the cords are further divided into five terminal branches at the axilla level.…”

“…The root of C5 contributes to the formation of the dorsal scapular nerve, together with the roots of C3-C4 and the cranial nerve XI they form the motor pathway for the levator muscle of the scapula and the rhomboid muscles [22]. The suprascapular nerve derives from the upper trunk of the BP from C5-C6 and has motor functions for the supraspinatus and infraspinatus muscles, and with sensitive functions for the shoulder area (70% of the sensitivity of the shoulder) [15]. The subclavius nerve starts from C5-C6 (motor nerve); the subscapular nerves (C5-C6) derive from the posterior cords of the BP, with an upper and lower branch innervating the subscapular muscle and the teres major muscle [15].…”