An electroneurography-based assay for identifying injured nerve segment during surgery: design and in vivo application in the rat.

OBJECTIVE: Nerve injury is the main reason for nerve reconstruction surgery, during which the surgeon must determine the location of the injured nerve segment, resect it, and reconnect the remaining healthy nerve stump ends within a limited time. Given this importance, an assay needed to determine the exact location of the injured nerve segment, but no tool has yet fulfilled this need so that a visual inspection of the nerve is still the primary method of identifying the injured segment. APPROACH: We designed a flexible multi-electrode array sensor that records the electroneurographic signal (ENG) as the action potential elicited by electrical stimulation that propagates along the nerve upon both orthodromic and antidromic stimulation. Its utility was validated by in vivo experiments in injured sciatic nerves of rats. MAIN RESULTS: The results showed that the first post stimulus negative electroneurographic component (N1) is the most valid neural correlate, as its amplitude decreased, and latency increased as the action potential propagated across the injured segment. Gradual recovery of nerve conduction was observed when measured immediately, 7, and 30 d after injury. The locations of the identified injured segments were validated by histological findings. SIGNIFICANCE: The sensor and the algorithm developed in this study are breakthroughs in surgical nerve assessment accomplished by determining the specific nerve segment that should be resected, enabling the optimal surgical outcome.