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The plexus is formed by the ventral rami of spinal nerves C5–8 and T1. These are the roots of the brachial plexus that supplies the upper limb. C5–8 emerge into the neck between scalenus anterior and medius. T1 emerges inferior to the neck of the first rib, but joins the plexus above the apex of the lung. C5 and C6 form the upper trunk, C7 continues as the middle trunk, while C8 and T1 form the lower trunk. The trunks pass laterally and lie around the subclavian artery while passing over the first rib to enter the axilla, between the clavicle and the scapula. Behind the clavicle, each trunk splits into anterior and posterior divisions. These recombine to form the posterior , lateral and medial cords around the axillary artery. The upper roots (C5–7) tend to stay lateral, the lower roots (C8,T1) tend to stay medial. All roots contribute to the posterior cord, and therefore also to the radial nerve. The median nerve is formed from both lateral and medial cords, therefore also contains all roots. Proximal muscles tend to be supplied by nerve roots that emerge from higher segments of the spinal cord. Distal muscles are supplied by nerves arising from the lower segments. The five main branches of the brachial plexus are median , ulnar , radial , axillary and usculocutaneous nerves. Branches from both lateral and medial cords supply the pectoral muscles. After supplying the pectorals and contributing to the median nerve, the lateral cord becomes the usculocutaneous nerve. Subscapularis, teres major and latissimus dorsi are supplied by the posterior cord, which also gives the axillary nerve to deltoid and teres minor before continuing as the radial nerve. The medial cord contributes to the median nerve, and also gives cutaneous nerves to the medial arm and forearm before continuing as the ulnar nerve. Upper trunk injury removes C5 and C6, which supply the shoulder abductors and external rotators, and the elbow flexors and supinators. Consequently, the upper limb lies at the side adducted and internally rotated. The elbow is extended and pronated. The fingers may flex slightly and the condition, Erb’s palsy, is often called ‘waiter’s tip’ palsy. Lower trunk injury (Klumpke’s paralysis) removes C8 and T1, therefore all the thenar and hypothenar muscles are affected, along with the lumbricals and interossei. The hand is flattened and the fingers clawed.

Powerpoint Presentations:

An Interactive Brachial Plexus Web Based Tutorial

How to Draw the Brachial Plexus

BRACHIAL PLEXUS LESIONS FUNCTIONAL EVALUATION

Understanding Shoulder Dystocia and Brachial Plexus Injury

BRACHIAL PLEXUS BLOCK

Brachial Plexus Injury