A 62-year-old woman comes to the office for follow-up a month after undergoing left mastectomy and axillary lymph node dissection for invasive ductal carcinoma. Today, the patient feels well overall but reports continued burning and aching in her left upper arm, despite physical therapy. Examination of the left chest wall shows a healing incision without erythema and mild but appropriate edema of the left chest wall and axillary soft tissues. Sensation is diminished in the medial upper arm, near the axilla. Shoulder range of motion is normal, and the rest of the physical examination is unremarkable. Injury to which of the following nerves is most likely responsible for this patient's symptoms?
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This patient who underwent axillary lymph node dissection has persistent sensory dysfunction (eg, burning, aching, diminished sensation) in her medial upper arm, findings consistent with intercostobrachial nerve injury. The intercostobrachial nerve is a purely sensory nerve that typically originates from the second intercostal nerve's lateral cutaneous branch and then traverses the axilla to innervate the skin of the axilla and medial upper arm.
The intercostobrachial nerve is the most frequently injured nerve (whether by stretching or transection) during axillary lymph node dissection. However, injuries to other at-risk nerves are often more feared due to the resultant motor deficits:
Long thoracic nerve (serratus anterior): Damage results in scapular winging and weakness of arm abduction above the horizontal level.
Thoracodorsal nerve (latissimus dorsi): Damage results in loss of powerful adduction of the arm and weakness while extending and medially rotating the arm (Choice D).
Medial pectoral (pectoralis minor and major) and lateral pectoral (pectoralis major) nerves: Damage results in weakness while adducting and medially rotating the arm. In addition, there may be weakness flexing (clavicular head) or extending (sternocostal head) the humerus. (Choice B)
This patient has normal shoulder range of motion and an otherwise unremarkable examination (ie, no motor weakness), making injury to these nerves less likely. In addition, because the long thoracic, thoracodorsal, and medial and lateral pectoral nerves are primarily motor nerves and not responsible for any cutaneous sensation, their injury would not explain this patient's sensory deficits.
(Choice C) The suprascapular nerve provides sensation to the shoulder joint (glenohumeral and acromioclavicular joints) and motor innervation to the supraspinatus and infraspinatus muscles. It branches off the upper trunk of the brachial plexus and travels posteriorly towards the suprascapular notch of the scapula, where it is prone to injury; it does not travel through the axilla and is not at risk during axillary dissection.
Educational objective:
Multiple nerves are at risk for injury during axillary lymph node dissection. Intercostobrachial nerve injury results in sensory dysfunction (eg, burning, numbness) to the skin of the axilla and medial upper arm. Injury to the long thoracic (serratus anterior), thoracodorsal (latissimus dorsi), medial pectoral (pectoralis minor and major), or lateral pectoral (pectoralis major) nerves results in motor deficits to corresponding muscles.