Fluorescently Labeled Peptide Highlights Degenerated Facial Nerve Branches during Surgery

Abstract

Objectives: Nerve degeneration after transection decreases intraoperative visibility under white light (WL), complicating repair and increasing the risk of additional injury to surrounding tissue. We previously described F-NP41, a fluorescently-labeled peptide which highlights peripheral nerves following systemic injection. In this study, we analyzed whether F-NP41 highlights degenerated nerves and evaluated the use of additional fluorescence guidance in delayed facial nerve repair procedures. Methods: Degenerated distal facial nerve branches were imaged under WL and with fluorescence after systemic F-NP41 application 1, 2, 3, 6, and 9 months (n = 4 per time point) after main branch transection. Nerve to non-nerve tissue contrast was compared. Facial nerve repair surgeries with a cable graft were performed 6 weeks after transection, using WL alone (n = 9) or additional fluorescence guidance (n = 10). Time to nerve identification and total operating time were measured; postoperative functional recovery was assessed weekly by quantitative measurement of whisker movement for 6 weeks. Results: Nerve to non-nerve tissue contrast was increased >2-fold using fluorescence imaging versus WL at all time points ( P < .001). Fluorescence guidance decreased time to intraoperative nerve stump identification by 39% ( P < .0001). Postoperative functional recovery was similar for both groups after 6 weeks, although the rate of recovery tended to be increased after surgery with fluorescence guidance. Conclusions: F-NP41 significantly improves intraoperative visualization of degenerated nerves in mice up to nine months following injury compared with WL alone. The use of F-NP41 decreases intraoperative time to nerve identification by nearly 40%, thus reducing operating time and potentially improving functional recovery.