Long thoracic nerve

At a glance

English

Long thoracic nerve

Latin (TA2)

Nervus thoracicus longus

System

Nerve

Region

Neck

Side

Paired, left and right

About the long thoracic nerve

The long thoracic nerve, once called the external respiratory nerve of Bell or the posterior thoracic nerve, is the nerve of serratus anterior. It is built from branches of the anterior rami of C5, C6 and C7, taken directly from the roots of the brachial plexus. The C7 contribution is sometimes missing.

The upper two roots usually pass through the middle scalene, while the C7 root runs across its front; the parts then unite in the lower neck. The nerve drops through the cervicoaxillary canal behind the clavicle, keeping posterior to the axillary vessels and the plexus. It then reaches the outer face of serratus anterior on the side wall of the thorax, and travels down this surface roughly in the mid-axillary line to the lower edge of the muscle, giving a filament into each of its slips (digitations) along the way.

Serratus anterior holds the scapula flat against the ribs and pulls it forwards around the chest, as in reaching and punching. It also turns the scapula so that the glenoid faces upwards, which is needed to raise the arm fully above the head. A working long thoracic nerve is therefore essential for overhead movement and for pushing.

Because the nerve is long and lies near the surface of the chest wall, it is easily hurt. Causes include a blow to the side of the chest below a raised arm, prolonged carrying of heavy loads over the shoulder, surgery that clears the axillary lymph nodes, and neuralgic amyotrophy (Parsonage-Turner syndrome). Paralysis of serratus anterior lets the medial border of the scapula stand away from the ribs, a winged scapula, seen best when the patient pushes against a wall with straight arms. Pain may be slight, and the winging may only become obvious weeks later once trapezius has stretched.

Course and supply

Arises from

Anterior rami of C5, C6 and C7 at the roots of the brachial plexus; the C7 part is sometimes absent.

Ends in

Ends on the lower border of serratus anterior after giving a branch to each digitation of the muscle.

Supplies

Motor to serratus anterior, which protracts the scapula, holds it against the chest wall and rotates it upwards for raising the arm overhead. It has no cutaneous branch.