Lateral Pectoral Nerve at Shoulder

nervus pectoralis lateralis (ad humerum)

The lateral pectoral nerve arises from the lateral cord of the brachial plexus (C5, C6, C7) and pierces the clavipectoral fascia to supply the upper portion of pectoralis major (clavicular head and upper sternal head). It communicates with the medial pectoral nerve via the pectoral loop across the front of the axillary artery.

Region: Shoulder

Clinical Relevance

Clinical Notes

The lateral pectoral nerve is preserved during axillary lymph node dissection when the dissection stays lateral to the medial pectoral neurovascular pedicle. Its injury during medial dissection produces upper pectoralis major weakness and wasting of the clavicular pectoral head. The pectoral loop formed with the medial pectoral nerve explains why injury to one pectoral nerve alone produces incomplete pectoralis major atrophy. EMG distinguishes lateral from medial pectoral nerve injury level.

Pathology

Common Injuries & Conditions

Upper Pectoralis Major Atrophy

Wasting of the clavicular and upper sternal heads of pectoralis major from lateral pectoral nerve injury during axillary or pectoral surgery, producing visible anterior chest asymmetry and reduced shoulder adduction and internal rotation power.