Intraoperative real-time fluorescence labeling of degenerated facial nerves with bevonescein

Authors: Crawford KL, Berman E, Whitney MA, Adams S, Orosco RK, Nguyen QT

Affiliation: Oregon Health & Science University; University of California–Berkeley; University of California–San Diego; University of New Mexico

Journal: Plastic and Reconstructive Surgery, January 2026

PMID: 40208969

Introduction

Delayed facial nerve reconstruction is limited due to difficulty with identification of distal facial nerve segments with increasing time from injury. Producing a more reliable mechanism of identifying degenerated nerve segments is needed. Oxazine-4 has demonstrated to label nerves in a variety of experimental conditions, but its myelin-binding mechanism of action limits its ability to label chronically degenerated nerves. Bevonescein is hypothesized to be able to label degenerated facial nerve segments due to its extracellular matrix binding mechanism.

Methods

Sixteen mice underwent exploration of facial nerve. A 3 mm segment of the marginal mandibular branch was resected, ensuring that buccal branch was intact. Ten total mice were analyzed at 5 months post-transection. Mice tail vein injection of bevonescein and oxazine was done and imaging fluorescence of the facial nerve was completed.

Results

All marginal mandibular nerve segments were clearly visible with bevonescein under fluorescence microscopy. In contrast, only 4 of 10 mice had visible degenerated nerve segments. The mean signal-to-background ratio was significantly higher in the bevonescein cohort versus oxazine group for the degenerated segments (SBR 3.31 ± 1.11 vs 1.27 ± 0.54, P < 0.001. The fluorescence was similar for the intact buccal branch control nerve segment.

Conclusion

In a chronic murine facial nerve denervation model, bevonescein reliably labels degenerated nerves whereas the myelin-binding agent oxazine-4 does not meaningfully label chronically degenerated nerve segments.

Editorial Notes

Bevonescein (ALM 488, Alume Biosciences) is being evaluated in phase 2 clinical trials in head and neck surgery as an intraoperative fluorescent nerve imaging agent.