Musculocutaneous nerve

The musculocutaneous nerve is a terminal branch of the lateral cord of the brachial plexus. It originates in the axilla, near the lower border of the pectoralis minor muscle, and is composed of nerve fibers from the cervical spinal segments C5, C6, and C7.

Course of the nerve

After emerging from the axilla, the musculocutaneous nerve enters the anterior compartment of the arm by piercing the coracobrachialis muscle. It travels downward and obliquely through the arm, sandwiched between the biceps brachii muscle (on top) and the brachialis muscle (underneath).

As it approaches the elbow, the nerve moves toward the lateral side of the biceps tendon and pierces the fascia just above the elbow. After this point, it becomes the lateral cutaneous nerve of the forearm.

Branches of the musculocutaneous nerve

1. Muscular branches

• Coracobrachialis: The musculocutaneous nerve pierces this muscle to reach the anterior arm region.

• Biceps brachii (both short and long heads) and brachialis (lateral portion): The nerve supplies both these muscles as it traverses between them while descending through the upper arm.

2. Cutaenous branches

• The lateral cutaneous nerve of the forearm supplies sensory innervation to the skin on the lateral aspect of the forearm.

3. Articular branches

• A small branch accompanies the nutrient artery to supply the humerus via the nutrient foramen.

• Another small branch through the nerve to the brachialis muscle provides innervation to the elbow joint.