Most Dangerous Structure in Parotidectomy
The facial nerve (cranial nerve VII) is unequivocally the most dangerous structure at risk during parotidectomy, as its injury results in significant functional and quality-of-life morbidity including facial paralysis, and surgical planning must prioritize its identification and preservation. 1, 2
Why the Facial Nerve is the Critical Structure
The facial nerve traverses through the parotid gland, emerging from the stylomastoid foramen and dividing into temporofacial and cervicofacial divisions within the gland substance. 2 The entire surgical approach to parotidectomy is fundamentally designed around identifying and protecting this nerve, as reflected in major guidelines that explicitly state surgical extent should be limited when it would "place the facial nerve at significant increased risk." 1
The ASCO guidelines provide strong evidence-based recommendations (intermediate quality evidence, strong recommendation) that surgeons must perform facial nerve preservation in patients with intact preoperative facial nerve function when a dissection plane can be created between tumor and nerve. 1
Impact on Surgical Decision-Making
The primacy of facial nerve protection directly influences oncologic outcomes:
For T1-T2 low-grade tumors, partial superficial parotidectomy is recommended specifically to optimize tumor excision while minimizing risk to the facial nerve, even accepting close margins (≤5mm) that still achieve 90.6% 5-year disease-free survival. 1, 2
For advanced T3-T4 or high-grade cancers, guidelines recommend at least superficial parotidectomy but explicitly state that more aggressive surgery should only remove additional parotid tissue "when possible if it is deemed to not place the facial nerve at significant increased risk." 1
Facial nerve resection is only justified when branches are grossly encased/involved by confirmed malignancy or when preoperative facial nerve weakness exists, reflecting the severe morbidity of nerve sacrifice. 1
Anatomical Landmarks for Nerve Identification
Safe parotidectomy requires precise nerve identification using consistent anatomical landmarks:
The posterior belly of digastric muscle is the most reliable landmark, located 7.4-8.0mm from the facial nerve trunk and most easily identifiable during surgery. 3
The tympanomastoid suture is the closest landmark at 3.5-3.9mm from the nerve trunk, though requiring more complex dissection. 4, 3
The tragal pointer, while commonly referenced, is less reliable as it is cartilaginous, mobile, asymmetrical with irregular tip, and located 16-34mm from the nerve. 4, 3
Critical Pitfalls to Avoid
Anatomical variations pose significant risk: The facial nerve may have anomalous courses within the parotid, and the retromandibular vein may have abnormal relationships to facial nerve branches, increasing injury risk during dissection. 5, 6
Intraoperative decision-making must be cautious: Despite frozen section having 98.5% sensitivity and 99% specificity for malignancy, decisions causing major harm like facial nerve sacrifice should never be based solely on indeterminate preoperative or intraoperative diagnoses. 2
Objective assessment is mandatory: The House-Brackmann scale should be used to formally evaluate facial nerve function on postoperative day 1, at 1 month, and at 6 months, with facial nerve deficit defined as HB grade >II. 7