Which two nerves are at the highest risk of being damaged during axillary lymph node dissection?

Nerves at Highest Risk During Axillary Lymph Node Dissection

The intercostobrachial nerve (ICBN) and the long thoracic nerve are the two nerves at highest risk of damage during axillary lymph node dissection due to their anatomical location and course through the surgical field.

Intercostobrachial Nerve (ICBN)

Anatomical Considerations

• The ICBN is a lateral cutaneous branch of the second intercostal nerve that pierces the second intercostal space and traverses the axilla
• It provides sensory innervation to the medial and posterior aspects of the upper arm 1
• The ICBN is highly variable in its course and may present with different patterns, including bifurcation into multiple branches 2

Risk Factors for Injury

• The ICBN is particularly vulnerable during axillary dissection because:
  • It passes directly through the surgical field
  • It has variable anatomy that may not be immediately recognizable
  • It is often encountered early in the dissection when accessing level I lymph nodes 3

Consequences of Injury

• Damage to the ICBN results in:
  • Sensory loss (hypoesthesia) in the medial and posterior upper arm
  • Paresthesia (abnormal sensations like tingling or burning)
  • Dysesthesia (unpleasant abnormal sensations)
  • Persistent pain syndromes 4, 5

Long Thoracic Nerve

Anatomical Considerations

• The long thoracic nerve (nerve of Bell) runs along the lateral chest wall
• It innervates the serratus anterior muscle
• It typically courses along the mid-axillary line on the surface of the serratus anterior 1, 6

Risk Factors for Injury

• The long thoracic nerve is at risk during axillary dissection because:
  • It runs along the lateral chest wall in the operative field
  • It may be difficult to identify during surgery
  • It can be damaged by traction, compression, or direct trauma during dissection 6

Consequences of Injury

• Damage to the long thoracic nerve results in:
  • Serratus anterior muscle paralysis
  • Winged scapula (prominence of the medial border of the scapula)
  • Shoulder dysfunction and weakness
  • Pain and limited range of motion 6

Why These Nerves Are Particularly Vulnerable

1. Anatomical Position: Both nerves traverse the axillary space where lymph node dissection is performed 1

2. Surgical Approach: The standard transverse incision in the low axilla from the pectoralis major border to the anterior border of the latissimus dorsi places these nerves directly in the surgical field 1

3. Visualization Challenges:

   • The ICBN can be difficult to identify due to its variable course and small size
   • The long thoracic nerve may be obscured by lymphatic or fatty tissue 1, 6

4. Proximity to Target Structures: Both nerves are in close proximity to axillary lymph nodes that need to be removed 7

Clinical Implications and Prevention Strategies

For ICBN:

• Studies show that preservation of the ICBN reduces the area of long-term axillary hypoesthesia 4
• The ICBN can serve as an anatomical landmark dividing the axillary space into upper and lower parts 7
• When possible, preservation rather than transection is recommended 3

For Long Thoracic Nerve:

• EMG studies have shown that 11.3% of patients experience long thoracic nerve injury after ALND, with 2.27% having persistent injury at 12 months 6
• Lower BMI is associated with higher risk of long thoracic nerve injury 6
• Careful identification and preservation of the nerve is essential to prevent winged scapula and shoulder dysfunction 1

Surgical Technique to Minimize Nerve Injury

1. Careful Dissection: Use meticulous dissection techniques with good visualization of the surgical field

2. Nerve Identification: Actively identify both nerves early in the procedure 1

3. Minimize Traction: Avoid excessive traction which can cause neurapraxia even without direct nerve injury

4. Consider Nerve-Sparing Approaches: When oncologically appropriate, consider sentinel lymph node biopsy (SLNB) instead of complete ALND to reduce the risk of nerve damage 3

5. Surgical Expertise: The success and safety of lymph node procedures depend significantly on surgical expertise 1

By understanding the anatomical course of these nerves and employing careful surgical techniques, surgeons can minimize the risk of nerve injury during axillary lymph node dissection, thereby reducing post-operative morbidity and improving quality of life outcomes for breast cancer patients.