Facial Nerve Branching Patterns Vary With Vascular Anomalies

At our institution, in vivo facial nerve mapping (FNM) is used during vascular anomaly (VAN) surgeries involving the facial nerve (FN) to create an FN map and prevent injury. During mapping, FN anatomy seemed to vary with VAN type. This study aimed to characterize FN branching patterns compared to published FN anatomy and VAN type.

Retrospective study of surgically relevant facial nerve anatomy.

VAN patients (n = 67) with FN mapping between 2005 and 2018 were identified. Results included VAN type, FN relationship to VAN, FNM image with branch pattern, and surgical approach. A Fisher exact test compared FN relationships and surgical approach between VAN pathology, and FN branching types to published anatomical studies. MATLAB quantified FN branching with Euclidean distances and angles. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) analyzed quantitative FN patterns amongst VAN types.

VANs included were hemangioma, venous malformation, lymphatic malformation, and arteriovenous malformation (n = 17, 13, 25, and 3, respectively). VAN FN patterns differed from described FN anatomy (P < .001). PCA and HCA in MATLAB-quantified FN branching demonstrated no patterns associated with VAN pathology (P = .80 and P = .91, one-way analysis of variance for principle component 1 (PC1) and priniciple component 2 (PC2), respectively). FN branches were usually adherent to hemangioma or venous malformation as compared to coursing through lymphatic malformation (both P = .01, Fisher exact).

FN branching patterns identified through electrical stimulation differ from cadaveric dissection determined FN anatomy. This reflects the high sensitivity of neurophysiologic testing in detecting small distal FN branches. Elongated FN branches traveling through lymphatic malformation may be related to abnormal nerve patterning in these malformations.

NA Laryngoscope, 130:2708-2713, 2020.