During a parotid gland surgery, the facial nerve is at highest risk of injury at which anatomical site?

Explanation

## Most Common Site of Facial Nerve Injury During Parotid Surgery **Key Point:** The **parotid plexus** (the branching network of the facial nerve within the parotid gland) is the most common site of iatrogenic facial nerve injury during parotid surgery because the nerve is most exposed and vulnerable within the gland substance. ### Anatomical Course of the Facial Nerve ```mermaid flowchart TD A[Facial nerve exits stylomastoid foramen]:::outcome --> B[Enters parotid gland]:::outcome B --> C[Divides into parotid plexus]:::outcome C --> D[Main branches: Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical]:::outcome D --> E[Exits parotid as 5 terminal branches]:::outcome style A fill:#e8f4f8 style B fill:#fff4e6 style C fill:#ffe6e6 style D fill:#f0e6ff style E fill:#e8f4f8 ``` ### Why the Parotid Plexus is Most Vulnerable | Site | Frequency of Injury | Reason | Surgical Relevance | |------|-------------------|--------|--------------------| | **Parotid plexus** | 40–60% | Extensive branching within gland; most exposed during dissection | Main risk during superficial/total parotidectomy | | **Stylomastoid foramen** | 10–15% | Nerve exits here but injury rare; protected by bony landmark | Identifiable landmark; used for nerve identification | | **Pes anserinus** | 5–10% | Terminal branching outside gland; less commonly injured | Injury causes localized branch dysfunction | | **Geniculate ganglion** | <1% | Located in temporal bone; not exposed during parotid surgery | Not at risk in parotid procedures | **High-Yield:** The **stylomastoid foramen** is used as a surgical landmark to **identify** the facial nerve during parotidectomy, but the nerve is most at risk **within the parotid gland** where it branches extensively into the parotid plexus. ### Clinical Consequences of Parotid Plexus Injury - **Immediate:** Facial paralysis (partial or complete depending on extent) - **Delayed:** Synkinesis, contracture, aberrant regeneration - **Incidence:** 20–65% temporary paralysis; 1–5% permanent paralysis with modern surgical technique **Clinical Pearl:** Intraoperative facial nerve monitoring (electromyography) and careful identification of the nerve trunk at the stylomastoid foramen before entering the gland substance significantly reduce the risk of injury. **Mnemonic — Facial Nerve Course (SPPB):** - **S**tylomastoid foramen (exit point from skull) - **P**arotid gland (enters and branches) - **P**arotid plexus (main branching network — highest injury risk) - **B**ranches (5 terminal branches exit) **Warning:** Do NOT confuse the **parotid plexus** (branching within the gland) with the **cervical plexus** (C1–C4 nerve roots in the neck). The facial nerve plexus is entirely within or at the surface of the parotid gland.