Overview
The medial and lateral pectoral nerves carry motor signals from the brachial plexus to the pectoral muscles. Their names refer to the cords they arise from, not where they sit on the chest.
Origin and Course
The lateral pectoral nerve usually arises from the lateral cord and carries mainly C5-C7 fibres. The medial pectoral nerve arises from the medial cord and usually carries C8-T1 fibres. Connections between them can form a loop in front of the axillary artery.
Function
Together they supply pectoralis major. The medial pectoral nerve also commonly pierces and supplies pectoralis minor.
Common Injuries
Isolated injury is uncommon but may occur with surgery, traction or a broader brachial plexus injury.
Pain and Weakness Patterns
Weakness may affect pressing, adduction and internal rotation. These nerves do not provide the main skin sensation over the chest.
Clinical Relevance
Their variable branching matters during breast, chest and shoulder surgery. Muscle weakness should be interpreted alongside tendon integrity and other nerve findings.
Related Anatomy
References
- Standring S, ed. Gray's Anatomy. 42nd ed. Elsevier; 2020.
- Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. 9th ed. Wolters Kluwer; 2023.