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Nerve to Brachialis

nervus musculi brachialis

The brachialis receives dual innervation from the musculocutaneous nerve (C5, C6) to the medial two-thirds and from the radial nerve (C7) to the lateral third. The musculocutaneous branches are the primary motor supply, while the radial contribution to the lateral brachialis is phylogenetically older and clinically important in musculocutaneous nerve lesions.

Region: Upper Arm

Clinical Relevance

Clinical Notes

The dual innervation of brachialis means that isolated musculocutaneous nerve palsy preserves some elbow flexion via the radial nerve supply to the lateral brachialis, distinguishing it from complete elbow flexor paralysis. This partial preservation prevents the characteristic complete paralysis seen in isolated biceps palsy. The nerve to brachialis is preserved during lateral approaches to the humerus by staying anterior to the radial nerve.

Pathology

Common Injuries & Conditions

Musculocutaneous Nerve Palsy

Loss of biceps and coracobrachialis with partial brachialis preservation from radial nerve dual supply, producing weakened but not absent elbow flexion and lateral forearm numbness from loss of the lateral cutaneous nerve of the forearm.