# Posterior Belly of the Digastric Muscle as a Reliable and Consistent Landmark for the Identification of the Facial Nerve Trunk During Parotidectomy

## TL;DR

This study shows that the posterior belly of the digastric muscle is a reliable landmark for locating the facial nerve during parotid surgery, helping prevent nerve damage.

## Contribution

The study confirms the PBDM as a consistently reliable anatomical landmark for facial nerve identification in parotidectomy.

## Key findings

- The facial nerve trunk was located 15-20 mm superior and medial to the PBDM insertion.
- The PBDM-FNT distance was significantly greater than in previous studies, enhancing its reliability.
- No cases of facial nerve paresis were observed using this method.

## Abstract

Background

Identification and preservation of the facial nerve trunk (FNT) are critical during parotidectomy to prevent complications such as facial paralysis. Due to its anatomical proximity and accessibility, the posterior belly of the digastric muscle (PBDM) has emerged as a consistent and reliable intraoperative landmark for localizing the FNT. This study aims to review the experience of a single institution in superficial parotidectomy, with a focus on identifying the FNT using the PBDM.

Methods

This retrospective observational study reviewed 24 cases of parotidectomy performed at Safdarjung Hospital, New Delhi, from January 2021 to January 2024. Inclusion criteria included patients with parotid tumors, excluding those with preoperative facial nerve palsy or prior head and neck radiation or surgery. Key anatomical landmarks, such as the PBDM and tragal pointer, were used to identify the FNT.

Results

The PBDM was consistently identified as a reliable landmark. The FNT was located approximately 15-20 mm (17 ± 0.87 mm) superior and medial to the insertion of the PBDM. The distance from the PBDM to the FNT in this study was significantly greater compared to previous studies (p < 0.001), reinforcing its reliability as a consistent anatomical landmark. No cases of facial nerve paresis were observed.

Conclusion

The PBDM is a reliable and consistent landmark for FNT identification, minimizing the risk of facial nerve injury. This approach is valuable for optimizing outcomes in parotid surgery.