Extratemporal Facial Nerve Interconnections and Trunk's Variability: A Systematic Review with Meta-Analysis

Area of Science:

• Anatomy
• Surgical Anatomy
• Morphological Variability

Background:

• The extratemporal segment of the facial nerve (FN), including its trunk (FT) and branching patterns, exhibits considerable morphological variability.
• This variability has clinical significance, particularly in surgical procedures involving the head and neck.

Purpose of the Study:

• To systematically review and meta-analyze the morphological variability of the extratemporal facial nerve segment.
• To provide a comprehensive overview of the clinical significance of facial nerve extracranial division patterns.

Main Methods:

• A systematic review of four online databases was conducted following evidence-based anatomy guidelines.
• A meta-analysis of 19 eligible studies (2453 nerves) was performed using R programming software.
• Pooled prevalence of facial nerve variants, subgroup, and cumulative analyses were calculated.

Main Results:

• The most common facial nerve morphology was facial trunk (FT) bifurcation (94.1% prevalence).
• A single interconnection (IC) between temporofacial and cervicofacial branches occurred in 23.1% of cases.
• Two ICs were the rarest pattern, observed in 8.9% of cases.

Conclusions:

• The extratemporal facial nerve anatomy displays extensive morphological variability, challenging existing classification systems.
• While FT bifurcation is common (94.1%), distal branching patterns show significant diversity (8.9-23.1% for interconnections).
• Surgeons must be cautious during procedures like parotidectomy due to potential facial nerve injury risks stemming from anatomical variations.