Long Thoracic Nerve

Authors

Affiliations

Nate Yomogida, PT, DPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, PT, DPT

Doctor of Physical Therapy

B.A. in Neuroscience

Origin

The Long Thoracic Nerve originates from the anterior rami of C5, C6, C7¹.

Path

1. C5 and C6 along with the Dorsal Scapular Nerve pass through the Middle Scalene muscle; whereas C7 passes anterior to it¹.
2. The Long Thoracic Nerve then travels inferior to the brachial plexus and clavicle then superiorly to the 1st rib¹.
3. Next the LT nerve descends along the lateral aspect of the chest wall and innervates the Serratus anterior muscle.
4. The LT nerve extends as far inferior as the 8th or 9th rib¹.

Motor Innervation

Table 1: Long thoracic nerve Muscle Innervations

Muscle	Origin	Insertion	Innervation	Action
Serratus anterior	1-9 Ribs	Superior angle of Scapula (costal and dorsal surfaces) Medial border of scapula (costal surface) Medial border of scapula (costal surface) Inferior angle of Scapula (costal & dorsal surfaces)	Long thoracic n. C5 - C7	Superior part: Lowers raised arm Entire mm.: Protraction, Rib elevation (with fixed shoulder) Inferior part: Rotates scapula laterally forward

Function

• Since the Long Thoracic Nerve only originates from the anterior rami, it only has motor innervation.
• The Long thoracic nerve is the only innervation to the serratus anterior muscle¹.

Dysfunction

The long and superficial course of the Long Thoracic Nerve causes it to be susceptible to a variety of injuries:

1. Entrapment of the C5 and C6 when passing through the middle scalene muscle¹.
2. Compression of the Long Thoracic nerve via traction to the UE by the undersurface of the scapula, as the nerve crosses over the second rib¹.
3. “Compression and traction to the nerve by the inferior angle of the scapula during general anesthesia, or with vigorous passive abduction of the arm”¹.

“Lesions of the long thoracic nerve are common and are the single most common peripheral nerve lesion at the shoulder. The most common cause of long thoracic nerve injury results from carrying a heavy object on the shoulder. Other causes include postinfection, postinjection, postpartum, and postoperative origins.16 Similar to other peripheral nerve injuries, trauma to the nerve can be caused by a direct blow or a traction force to the nerve.”¹

“The traction injury can occur when concurrent head rotation away, side bending away, and neck flexion are coupled with the arm positioned overhead. Other mechanisms that have been attributed to long thoracic nerve dysfunction include lifting weights overhead, driving a golf ball, and serving a tennis ball.16”:¹

Clinical Presentation

Long Thoracic Nerve dysfunction generally presents as:

• “Vague pain in the neck and the scapula region”¹.
• “An inability to fully elevate the arm overhead”¹.
• “Shoulder flexion and abduction are weak and limited in active range of motion (AROM) due to the loss of the trapezius–serratus anterior force couple”
  • (see Chapter 16 of Dutton¹).
• Scapular winging

Intervention

Conservative intervention includes:

• Protection of the serratus anterior with a brace or restraint¹
• Muscle taping¹
• Strengthening exercises for the rhomboids, pectoralis, trapezius, and serratus anterior muscles¹.

References

1.

Dutton M. Dutton’s Orthopaedic Examination, Evaluation, and Intervention. 5th ed. McGraw Hill Education; 2020.