Rapid Intraoperative Fluorescence Assessment of Nerve Damage - PROJECT SUMMARY Acute peripheral nerve crush injuries frequently result from closed or open fractures, joint dislocations, and high energy collisions. Nerve compression can lead to functional deficits ranging from paresthesias to complete motor and sensory function loss, affecting -1.6 million trauma patients annually. Assessment of the degree of injury and the possibility for functional recovery versus the need for amputation or complete nerve transfer after injury remains challenging and to date no objective methodology exists to aid in immediate decision-making at the time of injury. Scoring systems have been developed with threshold values for amputation, however their utility to date has been inconclusive. Thus, surgeons are left to make nerve damage assessments via gross visual examination, which cannot resolve the degree of axonal disruptions and/or tissue degradation, leaving -50% of patients with poor functional recovery outcomes. We hypothesize that fluorescence guided surgery (FGS) using a nerve-specific fluorophore could provide an objective methodology to determine the degree and recoverability of nerve injury, guiding surgical intervention. Over the past 10 years, our group has worked on the development of nerve-specific fluorescent contrast to improve intraoperative nerve visualization. We have developed a library offirst-in-kind, small molecule, targeted, near-infrared (NIR) fluorophores that label nerve tissue with high affinity, which are currently undergoing preclinical pharmacology and toxicology testing for first-in-human (FIH) clinical trials. These fluorophores provide nerve visualization with high contrast at millimeter to centimeter tissue depths in mice, rats and swine facilitating clear identification between healthy and injured nerve tissues following topical/paint-on or systemic administration. We propose to fully characterize the fluorescent uptake profiles and intensity differences seen between healthy and damaged nerve tissue using our NIR nerve-specific fluorophores to provide an objective methodology for intraoperative nerve damage assessment. This study's immediate milestones will include (1) selection of an optimal imaging time point for the nerve damage assessment methodology, (2) quantification of fluorescence intensity, nerve to surrounding tissue ratios and uptake parameters in healthy, permanently damaged. and recovering nerve tissue in mouse sciatic nerve iniury models and (3) validation of the developed nerve damage assessment methodology in a blinded mouse sciatic nerve iniury study for future clinical translation. We will leverage the expertise of our team in nerve contrast agent development, nerve-specificity quantification, pharmacology assessment and nerve injury models to complete the following: Aim 1: Develop a nerve damage assessment methodology to objectively guide surgical decisions. Aim 2: Validate the most predictive nerve damage assessment methodology in a blinded study for future clinical translation. Completion of these studies will result in the first objective nerve damage assessment methodology for trauma surgery utilizing novel NIR nerve-specific fluorophores developed by our team. The proposed method development and validation will provide important proof-of-concept for future clinical translation.
