Background: The preoperative diagnostic imaging of peripheral nerve lesions and the postoperative monitoring of microsurgically coapted nerves remain unsolved problems. The aim of this study was to investigate peripheral nerve regeneration after complete neurotmesis with magnetic resonance imaging techniques.
Methods: Study groups included 70 rats. Their right sciatic nerve was either cut and left untreated or epineurially coapted. After postoperative days 3, 6, 10, and 14 and then weekly until postoperative day 84, these rats underwent scanning at 4.7 T. T2 signal intensities of the nerves were analyzed. In parallel, on postoperative days 3, 6, 10, 14, 21, 28, 42, 63, or 84, rats were killed for histologic processing. These findings were related to the corresponding images.
Results: After an initial T2 signal increase of the nerves in both groups, the coapted group demonstrated a major T2 signal decrease in the distal part of the nerve after postoperative day 21, whereas in the unrepaired group a signal decrease was not observed until postoperative day 42. Differences between the two groups were significant at postoperative days 3, 6, and 28 and thereafter. The signal decrease in the coapted nerves could be correlated to the ingrowth of regenerating axons observed by histology. Moreover, the continuity of coapted nerves or an explicit gap in the unrepaired group was detectable at every time point.
Conclusions: This study presents novel magnetic resonance imaging data regarding regeneration after neurotmesis. High-field-strength magnetic resonance imaging has the potential to diagnose a discontinuity within a nerve of interest and monitor its regeneration after coaptation.