# The Relationship Between the Retromandibular Vein and the Extratemporal Segment of the Facial Nerve: A Prospective Cadaveric Study of 24 Hemifaces

## TL;DR

This study maps the anatomical relationship between the facial nerve and retromandibular vein in cadavers to help surgeons avoid nerve damage during parotid surgery.

## Contribution

The study identifies three distinct anatomical patterns of the facial nerve relative to the retromandibular vein and proposes a classification system.

## Key findings

- Three anatomical patterns of facial nerve and retromandibular vein relationship were identified in 24 cadaveric hemifaces.
- Type I (66.7%) had the nerve lateral to the RMV, Type II (29.2%) had the nerve superficial to the RMV with a deep mandibular branch, and Type III (4.1%) had the nerve medial to the RMV.
- Anatomical variations suggest surgeons should consider retrograde approaches when the facial nerve lies deeper relative to the RMV.

## Abstract

Introduction: Anatomical preservation and functional integrity of the facial nerve (FN) are the main concerns of parotid surgery. Even though a variety of anatomical landmarks have been proposed and widely utilized, temporal or permanent postoperative FN palsy is still a significant comorbidity of parotid surgery. Therefore, the literature must fully elucidate the consistency of the anatomical relationship between the FN and the retromandibular vein (RMV).

Methods: We conducted a cadaveric study of 24 hemifaces to map the relationship between the FN and the RMV. Three distinct patterns were identified. Fourteen of the hemifaces were males, and 10 were females. Thirteen cadaveric dissections were performed on the right side and 11 on the left side.

Results: Our study found three distinct patterns and proposed a classification system. Type I (66.7%) is when the nerve lies exclusively lateral to the RMV. Type II (29.2%) is when the FN lies superficial to the RMV, but its mandibular branch lies deep to the anterior branch of the RMV, and type III (4.1%) is when the FN lies exclusively medial to the RMV.

Conclusion: The FN and RMV relationship is not constant, and surgeons should be aware of every anatomical variation. Especially in cases where the FN is estimated to lie more in-depth to the level of the RMV, a retrograde approach may be required to avoid a FN injury.