Abstract
Peripheral facial nerve defects resulting from oncological resection necessitate early repair, and underscore the need for accurate intraoperative assessment of their extent. This study proposes a span-based classification system for peripheral facial nerve defects, based on the length and location of the defect. The system delineates specific defect characteristics and provides practical guidance for intraoperative decision-making and personalised repair plans.
Introduction
Surgical resection of maxillofacial tumours, particularly those involving the parotid gland, frequently results in injury to the peripheral facial nerve (FN). To minimise local recurrence, encapsulated FN segments are often excised along with the tumour, leading to FN defects of varying degrees. Immediate nerve anastomosis is regarded as the gold standard for optimising facial functional recovery. However, different lengths and types of defects require distinct repair techniques, ranging from the simplest end-to-end anastomosis to the most complex vascularised neuromuscular graft. Precise intraoperative evaluation and classification of FN defects are therefore critical to guide standardised and accurate nerve repair.
To address this issue, this article introduces a novel classification system for FN defects, based on our team’s extensive clinical experience in FN reconstruction. ,
Classification system
The system incorporates two key parameters: defect length and anatomical location. First, a “span-based” classification system of peripheral FN defects divided into four categories (I–IV), is proposed ( Fig. 1 ).
Schematic diagram of the span-based classification system for peripheral facial nerve defects. The yellow solid lines represent the anatomical course of the facial nerve (FN), while red dashed lines indicate the defective segments. Type I: Short gap amenable to tension-free, end-to-end anastomosis. Type II: Long gap with both proximal and distal stumps available. Type III: Proximal stump unavailable. Type IV: Distal stump unavailable.
Corresponding repair strategies are recommended for each type of defect ( Fig. 2 ). Specifically:
-
Type I defects: direct end-to-end anastomosis is preferred when tension-free coaptation is achievable.
-
Type II defects: nerve grafting, using sources such as the great auricular nerve (GAN) or sural nerve (SN), is the primary option.
-
Type III defects: where the proximal stump is absent and distal segments lack central neural input, nerve transfer techniques (for example, employing the masseteric, hypoglossal, or contralateral facial nerve) are typically utilised to provide an axonal source.
-
Type IV defects (the most challenging scenario): distal nerve branches are lost, and target muscles cannot be reinnervated via the FN. In such cases, surgeons may opt for vascularised muscle transplantation or static suspension, depending on clinical requirements.
