41

CASE 41


A 24-year-old woman was riding her horse in preparation for an upcoming equestrian event. At she approached one of the jumps, the horse suddenly stopped, throwing her to the ground. She landed violently on her shoulder and head causing excessive separation. The separation produced a brachial plexus injury.



WHAT IS THE ORGANIZATION OF THE BRACHIAL PLEXUS?


The brachial plexus is composed of the following elements: roots, trunks, divisions, cords, and branches (Fig. 6-1). The following mnemonic can be used to remember this basic organization: red tigers drink cold beer. The roots of the brachial plexus are ventral primary rami from C5, C6, C7, C8, and T1. The first pair, C5 and C6, joins to form the superior trunk, whereas C8 and T1 converge to form the inferior trunk. The middle trunk is simply a continuation of C7. Each trunk divides into an anterior division and a posterior division. The divisions then converge to form cords. The posterior cord is formed exclusively by the three posterior divisions, one from each of the three trunks. The anterior divisions form the lateral and medial cords. The anterior divisions from the superior and middle trunks unite to form the lateral cord, whereas the medial cord is simply a continuation of the anterior division from the inferior trunk. Each cord ends by dividing into two terminal branches. These are:


• Lateral cord — musculocutaneous nerve and the lateral root of the median nerve

• Medial cord — ulnar nerve and the medial root of the median nerve

• Posterior cord — axillary nerve and radial nerve

image

FIGURE 6-1 A, Brachial plexus structures in the neck and axilla. B, Schematic of the brachial plexus elements.


(Drake R, Vogl W and Mitchell A: Gray’s Anatomy for Students. Churchill Livingstone, 2004. Fig. 7-51.)



DESCRIBE THE SENSORY AND MOTOR FUNCTIONS OF THE VARIOUS ANATOMICAL LEVELS OF THE BRACHIAL PLEXUS.


The sensory and motor functions of various structural elements of the brachial plexus are described in Table 6-1.


TABLE 6-1 Sensory and Motor Functions of the Brachial Plexus at Different Anatomical Levels


















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Jun 16, 2016 | Posted by in ANATOMY | Comments Off on 41

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Anatomical Level Sensory Function Motor Function
Root of C5 Skin of lateral surface of arm and lateral surface of proximal forearm Lateral (external) rotation and abduction of the shoulder
Root of C6 Cubital fossa, lateral side of forearm inferior to C5, and thumb Flexion of elbow and extension and abduction of wrist (extensor carpi radialis longus muscle)
Root of C7 Digits 2,3, and 4 and dorsal-radial surface of hand