Root Origin
- Spinal nerve roots: C5, C6, C7
- Plexus: Brachial plexus — but the long thoracic nerve is an early branch that exits from the nerve roots directly, before the roots form the trunks. It does not pass through the trunk-division-cord pathway.
- Type: Motor only (pure motor nerve — no cutaneous sensory function)
Course
- Nerve root formation. The nerve forms from contributions of C5, C6, and C7 roots. The C5 and C6 contributions merge and pass through or behind the middle scalene muscle. The C7 contribution passes anterior to the middle scalene and joins the C5-C6 trunk inferiorly. This passage through the middle scalene is clinically significant — scalene hypertrophy or spasm can compress the nerve at its origin.
- Posterior to the brachial plexus. The fully formed nerve descends behind the brachial plexus and behind the axillary vessels, traveling along the lateral surface of the chest wall superficial to the serratus anterior.
- Lateral chest wall. The nerve descends vertically along the mid-axillary line on the superficial surface of the serratus anterior, from the axilla down to approximately the 8th or 9th rib. It is the longest nerve in the superficial thorax. Along its course, it gives off individual branches to each digitation of the serratus anterior.
- Terminal branches. The nerve innervates the serratus anterior from superior to inferior. The lower digitations (attached to the inferior angle of the scapula) receive the most substantial branches and produce the most powerful protraction and upward rotation force.
Motor Distribution
| Muscle | Action | Notes |
|---|---|---|
| anatomy/muscles/serratus-anterior | Scapular protraction, upward rotation, holds scapula against thoracic wall | The only muscle this nerve supplies. Loss = winged scapula — the medial border lifts off the rib cage during pushing or forward flexion of the arm. |
Sensory Distribution
- None. The long thoracic nerve is a pure motor nerve with no cutaneous sensory component. Damage produces weakness and scapular winging without numbness.
Entrapment Sites
1. Middle Scalene Muscle
- Location: Where the C5-C6 contributions pass through or behind the middle scalene
- Structure: Scalene hypertrophy, spasm, or fibrous bands within the muscle can compress the nerve roots before they form the long thoracic nerve
- Presentation: Gradual onset of scapular winging, often in overhead athletes (swimmers, baseball pitchers) or after repetitive heavy carrying (backpack palsy). No numbness.
- MT relevance: Scalene release may reduce nerve compression at this level. When treating the scalenes for thoracic outlet or cervical complaints, recognize that the long thoracic nerve passes through this region — resolution of scalene hypertonicity may also improve subtle scapular control problems.
2. Lateral Chest Wall (Direct Trauma or Stretch)
- Location: Along the mid-axillary line where the nerve travels superficially on the serratus anterior
- Structure: The nerve's long superficial course makes it vulnerable to direct compression (surgical positioning, seat belt injuries) and traction (heavy carrying with arm at the side, sudden overhead stretch)
- Presentation: Acute onset scapular winging after an identifiable event (surgery in lateral decubitus position, carrying heavy bags, forceful overhead activity). Can also occur as a viral neuritis (Parsonage-Turner syndrome) with sudden severe shoulder pain followed by serratus weakness.
- MT relevance: Be cautious with sustained deep pressure along the lateral chest wall, particularly in the mid-axillary line. The nerve is superficial here and can be irritated by aggressive lateral rib work. If a patient develops scapular winging after your treatment, the nerve may have been compressed — this is rare but possible.
Clinical Tests
| Test | Procedure | Positive Finding | What It Tells You |
|---|---|---|---|
| Wall push-up test | Patient faces a wall and performs a push-up (pushes against the wall with both hands). Observe the scapulae from behind. | The medial border of the scapula lifts off the thoracic wall (wings) on the affected side. | Serratus anterior weakness — the muscle cannot hold the scapula against the rib cage during protraction. This is the definitive test for long thoracic nerve palsy. |
| Forward flexion scapular observation | Patient raises both arms into full forward flexion while you observe the scapulae from behind. | Winging of the affected scapula, especially past 90 degrees of flexion where serratus anterior contribution to upward rotation becomes critical. | Serratus anterior insufficiency. More functional than the wall push-up test — shows the deficit during an everyday movement. |
| Serratus anterior MMT | Patient forward flexes the arm to 90 degrees and pushes forward against resistance (protraction). Observe the scapula. | Weakness of protraction with scapular winging under load. | Directly tests the muscle the long thoracic nerve innervates. Grade 0-5. Compare sides. |
Clinical Notes
- Winged scapula is a dramatic finding but not always the long thoracic nerve. Two nerves can produce scapular winging: the long thoracic (serratus anterior) and the dorsal scapular (rhomboids). The pattern differs. Serratus anterior winging: the medial border lifts during protraction (pushing) and forward flexion. Rhomboid winging: the medial border lifts during retraction. Serratus winging is far more common and functionally significant.
- Parsonage-Turner syndrome (neuralgic amyotrophy) can present as sudden winging. A viral or post-vaccination inflammatory neuritis that often targets the long thoracic nerve. Presents with severe shoulder pain for days to weeks, followed by sudden painless weakness and winging. The pain is disproportionate to the physical findings. If a patient reports intense shoulder pain that resolved, followed by arm weakness, think Parsonage-Turner. Recovery is slow — 12-24 months — but usually complete.
- Overhead athletes are at risk. Swimmers, baseball pitchers, tennis players, and volleyball players subject the long thoracic nerve to repeated traction during overhead activities. Gradual onset of scapular winging in an athlete often reflects cumulative nerve stretch rather than a single traumatic event. Scapular stabilization exercises and activity modification are the treatment — this is not a soft tissue problem that responds to massage alone.
- Serratus anterior weakness changes everything above the shoulder. Without the serratus anterior's upward rotation and protraction, the scapula cannot position itself properly for overhead movement. The result: impingement, rotator cuff overload, and shoulder pain. If a patient has refractory shoulder impingement, check for subtle serratus anterior weakness — you may be treating the rotator cuff while the scapula is the real problem.
- Do not confuse cosmetic winging with pathological winging. Some individuals — particularly thin, lean clients — have scapulae that appear prominent due to low body fat or habitual posture. True winging is dynamic: it appears or worsens with protraction and forward flexion. If the scapula lies flat at rest and only becomes prominent during active movement, that is pathological winging.
Related Nerves
- anatomy/nerves/dorsal-scapular-nerve — C5. Supplies the rhomboids and levator scapulae. The other "scapular nerve" — damage produces a different winging pattern (winging during retraction rather than protraction). Both nerves are early brachial plexus branches from the nerve roots.
- anatomy/nerves/suprascapular-nerve — C5-C6. Supplies the supraspinatus and infraspinatus. With the long thoracic nerve, these are the three nerves that control scapular mechanics and rotator cuff function. Scapular dyskinesis often involves compromise at multiple levels.
- anatomy/nerves/spinal-accessory-nerve — CN XI. Supplies the trapezius. Trapezius and serratus anterior work together for scapular upward rotation — if one is weak, the other must compensate, leading to muscle imbalance patterns.
Key Takeaways
- Sole supply to the serratus anterior — damage produces the classic winged scapula visible during wall push-ups and forward flexion.
- Pure motor nerve with no sensory component — winging occurs without numbness, distinguishing this from brachial plexus lesions.
- Passes through the middle scalene at its origin — scalene release may improve nerve function; recognize this relationship during thoracic outlet treatment.
- Serratus weakness undermines all shoulder mechanics — check for subtle winging in refractory shoulder impingement cases.