Improving Outcome of Nerve Regeneration after Repair through Comprehensive Assessment of the Lesioned Nerve Stump---Intraoperative Evaluation, Intervention, and Functional Outcome (I)

The quality of nerve stump in peripheral nerve repair is a fundamental issue in reconstruction surgery. Even with this level of importance, no methods have been applied to allow the surgeon to evaluate the nerve stump, a step that will determine which part of the nerve ending is not healthy enough and should be resected before neurorrhaphy. We then propose the present project to develop the method and instrument for nerve ending evaluation and will show the validity of this approach by demonstrating the degree to which the quality of nerve stump will affect the long-term outcome of a neurorrhaphy in a rodent model. The first specific aim of the present project is to establish a novel assay for nerve stump evaluation and translate the knowledge into a product-oriented instrument. The nerve is contacted with an electrode array that has multiple contact points and each of which can be used to deliver electrical stimulation and recording. The nerve stimulation and recording is coordinated so that the nerve conduction velocity and the amplitude of elicited responses will be analyzed by a computer program we develop. We then use the method to evaluate the quality of nerve stump that has received a variety of length and severity of mechanical trauma to establish the correlation between neurophysiological findings and nerve quality. The second specific aim is to construct the correlation between nerve stump quality and the neurophysiological and behavioral outcomes using a novel rodent neurotomy and neurorrhaphy model we recently developed for the mystacial pad. After the surgery, we then observe the recovery of sensory, motor and behavioral performance for at least 4 weeks to measure the outcome. For the motor function, we will analyze the whisker movement elicited by stimulation at the proximal stump of the repaired nerve or at the primary motor cortex. Novel electric and optogenetic stimulations will be applied and their reliability and validity will be compared. For the sensory function, we will analyze the neuronal activities recorded in the barrel cortex while we stimulating the animal’s whisker using piezoelectric motors we are developing. Again, both the traditional electrophysiological single-unit method and genetic in vivo ultrasensitive protein calcium sensors imaging (GCaMP6) method obtained through a two-photon microscope will be compared. For the composite motor-sensory behavior, we applied whisker discrimination task in which the animal has to use his vibrissa system to determine which texture is rougher in a two-alternative forced –choice design. The present subproject will provide the gold standard electrophysiological/behavioral evaluation platform for subproject 1 and cross-validation for subproject 3. The long-term objective of the present project is to develop a product that provides total solution for electrophysiological evaluation in the surgery room. The hypothesis we hold is that the quality of nerve ending will affect the outcome of reconstruction surgery and our method that applied “inching” method of nerve conduction study can evaluate the nerve quality along the continuities of a nerve stump.

Project ID:PC10408-1730
External Project ID:MOST104-2314-B182-050