What is the origin and management of long thoracic nerve damage?

Long Thoracic Nerve: Origin and Management of Damage

The long thoracic nerve (LTN) originates from the C5, C6, and C7 nerve roots and damage is best managed through early diagnosis with MRI imaging followed by conservative therapy for most cases, with surgical intervention reserved for persistent cases after 12-24 months of failed conservative treatment.

Anatomical Origin and Course

The long thoracic nerve is a mixed nerve containing both sensory and motor fibers that originates from the anterior rami of the cervical nerve roots C5, C6, and C7, with some anatomical variations:

• Most commonly formed by contributions from C5, C6, and C7 nerve roots 1, 2
• Less common variations include origins from C4-7, C5-8, or C6-7 1
• The C5 and C6 branches typically join beneath the scalenus medius muscle to form the upper division of the LTN 3
• The C7 contribution joins the upper division more caudally in the axillary region 2, 3
• The nerve travels on the surface of the serratus anterior muscle, providing 1-4 branches to each slip of the muscle 1

The LTN has a unique course:

• The upper portion (C5-C6 components) typically passes between the middle and posterior scalene muscles, sometimes through the middle scalene muscle 2
• The C7 component consistently travels anterior to the middle scalene muscle 2
• Average length of the LTN trunk is approximately 112 mm 1

Diagnosis of Long Thoracic Nerve Damage

Clinical Presentation

• Scapular winging is the hallmark manifestation of LTN neuropathy 4
• Patients may present with shoulder pain, weakness, and dysfunction 5
• Shoulder protraction test can specifically assess the function of the upper division of the LTN 3

Diagnostic Imaging

• MRI of the brachial plexus is the recommended imaging modality for diagnosing thoracic outlet syndrome and LTN damage 6

• The imaging protocol should include:

  • High-resolution T1-weighted and T2-weighted sequences in sagittal and axial planes 6
  • Evaluation in both neutral and arms-abducted positions to demonstrate dynamic compression 6
  • Orthogonal views through the oblique planes of the plexus 6

• Ultrasound can also be used to visualize the LTN from its origin to distal segments 4

Management of Long Thoracic Nerve Damage

Conservative Management (First-Line Approach)

• Conservative therapy is the initial treatment of choice for most cases of LTN injury 6, 5
• Treatment components include:
  1. Range of motion exercises for the shoulder 5
  2. Targeted physical therapy focusing on:
     • Strengthening of the serratus anterior muscle 5
     • Latissimus dorsi stretching and release 6
     • Postural correction 6
     • Strengthening of antagonist muscles 6
  3. Activity modification 6

Surgical Intervention

• Reserved for cases that fail to improve with conservative management after 12-24 months
• Surgical options may include:
  • Nerve decompression in cases where compression is identified
  • Surgical exploration and neurolysis
  • Nerve transfers in cases of severe injury

Rehabilitation

• Post-surgical rehabilitation is critical for long-term success 6
• Protocol typically includes:
  • Passive and assisted mobilization of the shoulder starting immediately post-surgery 6
  • Progressive strengthening exercises
  • Resistance strength training starting at 8 weeks postoperatively 6

Common Causes of Long Thoracic Nerve Injury

1. Iatrogenic causes:

   • Surgical procedures in the axillary region
   • Cervical nerve root or inter-scalene brachial plexus blocks 4
   • Thoracic surgeries

2. Traumatic causes:

   • Athletic activities causing stretch injuries 5
   • Direct trauma to the shoulder or neck region

3. Compression:

   • Thoracic outlet syndrome
   • Anatomical variations causing nerve entrapment

Prognosis and Outcomes

• Most cases of LTN injury from athletic activity have favorable outcomes with conservative management 5
• Recovery time varies from several months to over a year depending on the severity of injury
• Delayed diagnosis beyond 14 days can significantly worsen outcomes 6
• Inadequate treatment may lead to persistent symptoms and functional limitations

Clinical Pearls

• Always evaluate for scapular winging in patients with shoulder pain or dysfunction
• Consider LTN injury in athletes with shoulder pain after vigorous activity
• MRI is the preferred imaging modality, but avoid relying solely on axial imaging slices as this can lead to misrepresentation of the condition 6
• Conservative management should be given adequate time (12-24 months) before considering surgical intervention
• Post-treatment rehabilitation is essential for optimal functional recovery