Long thoracic nerve
Nervus thoracicus longus
Also known as: nerve of Bell, external respiratory nerve of Bell
A branch from the roots of the brachial plexus (C5–C7) that runs down the lateral chest wall on the surface of serratus anterior, which it supplies. Injury causes medial "winging" of the scapula.
Overview
The long thoracic nerve arises directly from the roots of C5, C6 and C7. The C5 and C6 contributions pierce the middle scalene. The nerve descends behind the brachial plexus and the first part of the axillary artery, crosses the first rib, and runs vertically down the external (superficial) surface of serratus anterior along the mid-axillary line. It gives a branch to each digitation of the muscle. Its long, superficial course on the lateral chest wall, covered only by skin and fascia, makes it vulnerable to direct injury and to stretching.
Serratus anterior protracts the scapula (punching, pushing) and, with trapezius, rotates it upward. This is essential for raising the arm above about 90°. It also holds the medial border of the scapula against the thoracic wall.
- Location
Root of the neck (through scalenus medius) → axilla → lateral thoracic wall on serratus anterior (mid-axillary line).
Anatomy
- Innervation
Serratus anterior.
- Nerve roots
C5, C6, C7 (from the roots, before the trunks form).
- Course
Roots C5–C7 → through or behind the middle scalene → behind the brachial plexus and axillary artery → over the first rib → descends on the lateral surface of serratus anterior in the mid-axillary line.
Function
- Protraction of the scapula (serratus anterior)
- Upward rotation of the scapula, allowing elevation of the arm above the head (with trapezius)
- Holds the scapula against the chest wall
Clinical significance
Winged scapula
Paralysis of serratus anterior lets the medial (vertebral) border and inferior angle of the scapula lift away from the chest wall. This is most obvious when the patient pushes against a wall or protracts the arms. The patient also cannot raise the arm fully above the head. Causes:
• surgery: axillary lymph node dissection or mastectomy, chest drain insertion, thoracotomy;
• trauma such as a blow to the lateral chest or a stab wound;
• carrying heavy shoulder loads ("rucksack palsy");
• neuralgic amyotrophy (Parsonage–Turner syndrome).
Lateral winging is different: it results from trapezius (CN XI) or rhomboid (dorsal scapular nerve) palsy.
Mnemonics
Roots
"C5, 6, 7 — raise your wings to heaven." The roots of the nerve that stops scapular winging.
Test yourself
After an axillary lymph-node dissection, a patient's scapula wings when she pushes against a wall. Which nerve was damaged?
- Thoracodorsal nerve
- Long thoracic nerve
- Accessory nerve
- Suprascapular nerve
Answer: Long thoracic nerve
The long thoracic nerve (C5–C7) runs on the superficial surface of serratus anterior in the medial wall of the axilla. Without serratus anterior, the medial border of the scapula lifts off the chest wall.
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.