Lateral Cord of the Brachial Plexus

fasciculus lateralis plexus brachialis

The lateral cord is formed by the anterior divisions of the superior and middle trunks (C5-C7) and lies lateral to the second part of the axillary artery, behind pectoralis minor. It gives off the lateral pectoral nerve and ends by dividing into the musculocutaneous nerve and the lateral root of the median nerve.

Anatomical Data

Course & Distribution

Origin	Anterior divisions of the superior and middle trunks (C5-C7)
Course	Runs through the axilla lateral to the second part of the axillary artery, deep to pectoralis minor, and ends at its lower border by dividing into its terminal branches
Motor	Pectoralis major, mainly the clavicular head (lateral pectoral nerve) Coracobrachialis, biceps brachii and brachialis (musculocutaneous nerve) Pronator teres and flexor carpi radialis (C6-C7 fibres in the median nerve)
Sensory	Lateral forearm (lateral cutaneous nerve of the forearm) Lateral palm and thumb, index and middle fingers (C6-C7 fibres in the median nerve)

Clinical Relevance

Clinical Notes

The lateral root of the median nerve joins the medial root in front of the axillary artery, forming a characteristic M shape that helps surgeons and ultrasound operators identify the cords during infraclavicular block. Lateral cord injury weakens elbow flexion (musculocutaneous nerve) and forearm pronation and wrist flexion (C6-C7 median fibres), with numbness of the lateral forearm. It can be damaged in anterior shoulder dislocation, gunshot or stab wounds of the axilla, and during axillary surgery.

Pathology

Common Injuries & Conditions

Lateral Cord Injury

Penetrating trauma or shoulder dislocation damaging the lateral cord causes weak elbow flexion and forearm pronation with numbness over the lateral forearm, while the intrinsic hand muscles are spared.

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