What nerves should be preserved during neck dissection?

Critical Nerves to Preserve During Neck Dissection

The four major cranial nerves that must be preserved during neck dissection are: CN VII (facial nerve), CN X (vagus nerve, including the recurrent laryngeal nerve), CN XI (spinal accessory nerve), and CN XII (hypoglossal nerve). 1

Primary Nerve Preservation Principles

When these nerves are functioning preoperatively, thorough efforts must be made to preserve their structure and function (main trunk and/or branches) even if otherwise adequate tumor margins are not achieved—recognizing that the surgeon should leave no gross residual disease. 1

Key Management Algorithm:

• If nerve is functioning preoperatively: Preserve the nerve at all costs, accepting closer margins if necessary, with adjuvant postoperative radiation or chemoradiation to address microscopic residual disease 1

• If nerve shows preoperative paralysis or direct tumor invasion: Segmental resection (and sometimes nerve grafting) may be warranted at the surgeon's discretion if tumor-free margins are assured throughout the remainder of the procedure 1

Specific Nerve Considerations

Spinal Accessory Nerve (CN XI)

The spinal accessory nerve is particularly vulnerable and represents the single most important source of long-term morbidity from neck dissection, as its injury causes trapezius dysfunction and "shoulder syndrome." 2, 3

Identification techniques to prevent injury:

• Use the superior sternocleidomastoid tendon (SST) and sternocleidomastoid branch of the occipital artery (SBOA) as landmarks: The SAN lies approximately 2.31 mm from the tendon and 3.63 mm from the artery 4

• Identify the anatomic triangle: Bordered by the SST laterally, SBOA medially, and digastric muscle superiorly—this triangle contains the SAN in 95.8% of cases 4

• Locate the constant vein crossing the nerve to aid in early identification 5

• Use the anatomy of the sternocleidomastoid muscle for consistent and rapid upper neck identification 6

Recurrent Laryngeal Nerve (RLN)

Routine recurrent nerve visualization and dissection is the surgical cornerstone for reducing nerve palsy during neck procedures involving thyroid or parathyroid regions. 1

Critical technical points:

• Complete visualization and nerve dissection from thoracic inlet to larynx is the gold standard 1

• Avoid blind ligatures or coagulation, especially in the tracheoesophageal groove 1

• The area near Berry's ligament and tubercle of Zuckerkandl (<2 cm tract) represents the highest risk zone where most lesions occur 1

• Use intermittent rather than continuous traction to prevent injury from excessive tension 1

• Prophylactic or therapeutic neck dissection increases risk of RLN injury and should be reserved for referral centers 1

Common Pitfalls and How to Avoid Them

• Continuous traction is the main cause of nerve injury (not surgical section, which is rare)—always use intermittent tension with cautious dissection 1

• Anatomical variations including nerve distortion by large goiters, precocious division of extralaryngeal branches, and intertwining between neural and arterial branches must be anticipated 1

• Despite nerve preservation attempts, 47% of patients may still show some trapezius atrophy and 20% may show little function even when the spinal accessory nerve is preserved 2

• Neck dissection with lymph node clearance increases the risk of definitive and transient unintentional nerve injuries 1

Documentation Requirements

• The operative dictation must include details of nerve identification and preservation status 1

• The neck dissection should be oriented or sectioned to identify levels of lymph nodes encompassed 1