From the Research
The long thoracic nerve is a motor nerve that originates from the anterior rami of cervical spinal nerves C5, C6, and C7, traveling along the lateral chest wall to innervate the serratus anterior muscle, and its dysfunction can lead to serratus anterior palsy, which should be suspected in patients with weak forward flexion and abnormal prominence of the medial edge of the scapula with weakness in shoulder protraction, as confirmed by a recent study 1. The primary function of the long thoracic nerve is to enable the serratus anterior muscle to stabilize the scapula against the thoracic wall and rotate it upward during arm elevation. When damaged, patients develop "winged scapula," a condition where the medial border of the scapula protrudes from the back when pushing against resistance, accompanied by weakness in forward flexion and abduction of the arm above shoulder level. This occurs because without proper serratus anterior function, the scapula cannot be held firmly against the thoracic wall during arm movements. Some key characteristics of the long thoracic nerve include:
- Originating from the anterior rami of cervical spinal nerves C5, C6, and C7
- Traveling along the lateral chest wall to innervate the serratus anterior muscle
- Vulnerable to injury during surgical procedures in the axilla, chest wall trauma, or from repetitive mechanical stress
- Playing a crucial role in stabilizing the scapula against the thoracic wall and rotating it upward during arm elevation
Treatment for long thoracic nerve injury typically involves physical therapy to strengthen surrounding muscles, with most cases resolving spontaneously within 6-24 months, as reported in a study 2. In persistent cases, nerve transfers or muscle transfers may be considered to restore shoulder function, with a recent study suggesting that direct transfer of the sternal head of the pectoralis major to the inferior pole of the scapula is a management option of choice for patients with disabling symptoms and no improvement despite physical therapy 1. Other treatment options include:
- Neurolysis
- Nerve transfer
- Tendon transfer
- Scapulothoracic arthrodesis, although this is an uncommon procedure, as noted in a study 3.
It is essential to diagnose long thoracic nerve dysfunction promptly and accurately, using physical examination findings, electromyography, and nerve conduction studies, as well as magnetic resonance imaging to show neurogenic fatty infiltration or atrophy, as discussed in a study 4. Early diagnosis and treatment can significantly improve outcomes and reduce the risk of long-term disability, as highlighted in a study 5.