Action:  Shoulder flexion

Nerves:  Axillary, medial and lateral pectoral, and musculocutaneous

Skeletal muscles: Deltoid, pectoralis major, long head of the biceps brachii, and coracobrachialis

Cutaneous distribution:  None except for the axillary and musculocutaneous nerves

Neuromuscular deficit:  Weakness/paralysis when flexing at the shoulder joint under resistance. Denervation is accompanied by muscular atrophy and deficit along the cutaneous distribution of the axillary (superior lateral brachial) and musculocutaneous (lateral antebrachial cutaneous) nerves.

Differential diagnosis:  Flexor weakness/paralysis plus cutaneous deficit along the upper lateral arm indicate impairment of the axillary (superior lateral brachial cutaneous) nerve, while cutaneous deficits that include the lateral forearm are diagnostic of musculocutaneous nerve dysfunction. Medial and lateral pectoral nerves have no cutaneous distributions in the upper limb.