Lateral pectoral nerve

At a glance

English

Lateral pectoral nerve

Latin (TA2)

Nervus pectoralis lateralis

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the lateral pectoral nerve

The lateral pectoral nerve leaves the lateral cord of the plexus, carrying fibres from C5, C6 and C7. In some people it comes straight off the anterior divisions of the superior and middle trunks before they unite. Despite its name it lies medial to the medial pectoral nerve for much of its course; the names describe the cords they come from, not their final positions on the chest wall. It is sometimes described as double, with two separate stems.

From its origin at the top of the axilla the nerve crosses in front of the first part of the axillary artery and vein. It then perforates the clavipectoral fascia, the sheet stretched between the clavicle and the upper border of pectoralis minor, above that muscle. Here it travels with the pectoral branches of the thoracoacromial artery and vein, forming a small neurovascular bundle, and splits into several branches that enter the deep surface of pectoralis major.

A loop, the ansa pectoralis, runs round the front of the axillary artery to connect the lateral pectoral nerve with the medial pectoral nerve. Through this loop some lateral fibres reach pectoralis minor, which is otherwise supplied by the medial nerve. The lateral nerve itself serves mainly the clavicular and upper sternocostal parts of pectoralis major, while the medial pectoral nerve takes the lower sternocostal fibres. Besides its motor fibres it carries sensory fibres from the muscle, including those for pain and position sense.

Pectoralis major adducts and medially rotates the arm, and its clavicular part also helps flex the shoulder, so injury to the nerve weakens these movements. Damage can occur in severe traction injuries of the brachial plexus and during operations on the front of the shoulder or chest wall, through stretching or diathermy. Anaesthetists block the pectoral nerves under ultrasound, in the plane between the two pectoral muscles, to give pain relief for surgery on the chest wall and shoulder. The neurovascular bundle with the thoracoacromial vessels is the usual landmark.

Course and supply

Arises from

Lateral cord of the plexus (C5 to C7), or straight off the superior and middle trunks' anterior divisions.

Ends in

Ends in several branches entering the deep surface of pectoralis major, with a communicating loop (ansa pectoralis) to the medial pectoral nerve.

Supplies

Motor to pectoralis major, chiefly its clavicular and upper sternocostal parts, and through the ansa pectoralis to part of pectoralis minor; carries sensory fibres from the muscle.