Zone of Nerve Injury
Defining the zone and severity of brachial plexus birth injury using Fluorescence lifetime imaging
Intraoperatively identifying the precise zone of injury peripheral nerve injuries (PNI) is difficult, thereby hindering recovery. A particularly devastating form of PNI is the brachial plexus birth injury – where obstetric complications lead to injury of the nerves controlling the newborn arm thereby leading to a paralyzed arm. Brachial plexus birth injury has an estimated incidence of 0.5 per 1000 births. In this population, gold standard studies such as electrodiagnostic and nerve conduction studies remain inaccurate (42-85% sensitivity), making recovery unpredictable with a 14-65% chance of complete recovery by 6 months of age. During surgical exploration of these injured nerves, the surgeon must decide which nerves are healthy enough to observe and those which require resection and reconstruction. Each millimeter of nerve trimmed is a millimeter of new nerve growth needed to reach its ultimate target, regenerating at a rate of 1 millimeter a day. If recovery hasn’t been achieved by 18 months the nerve endings at the muscle degenerate, leaving the muscle paralyzed.
Fluorescence lifetime imaging (FLIm) offers the potential for quick, label free, intra-operative assessment of in-continuity peripheral nerve injuries. FLIm uses ultraviolet laser pulses to excite endogenous tissue fluorophores and detect their fluorescent decay over time – generating real time tissue-specific signatures. FLIm distinguishes tissues based on their autofluorescence, spectral, and time-resolved characteristics. The time-resolved fluorescence decay adds specificity to the spectroscopic properties by capturing changes in the tissue microenvironment. These include physical and biochemical changes in structural proteins, metabolic co-factors, lipids, and porphyrins. FLIm has been successfully integrated intraoperatively by our collaborators to delineate tumor margins in the oropharyngeal cavity and brain gliomas. This approach, referred to as pulse sampling FLIm, utilizes handheld optical fiber probes to measure exposed tissue areas during surgery.
Dattesh R. Dave
University of California Davis Medical Center