Effects of External Beam Radiation in the Rat Tibial Nerve after Crush, Transection and Repair, or Nerve Isograft Paradigms

Introduction: In head and neck surgery, radiation therapy is often administered to an injured nerve. Previous studies have examined the effects of either preoperative or postoperative radiation on nerve regeneration in rodents. In these studies, histomorphometric analysis was performed up to 8 month postoperatively. Given the exceptional neuroregenerative capacity of rodents, significant differences in nerve regeneration may go undetected if nerves are evaluated at such distant postoperative time points. This study is designed with a more appropriate model and investigates the effects of radiation after three common nerve injury paradigms. Methods: Sixty-four Lewis rates were randomized to 8 groups corresponding to uninjured, tibial nerve crush, transection and repair, or reconstruction with isografts. Half of the animals in each of these paradigms (n = 8 per group) were treated with 10 Gy of external beam radiation to the site of nerve injury at 7 days postoperatively. On postoperative day 28, functional recovery and histomorphometric assessment was performed. Results: For a given paradigm of nerve injury, no significant differences in nerve fiber number, neural density, neural debris, or fiber width were noted between the control and radiated groups, and radiation did not affect functional recovery. Conclusion: Radiation had no discernible effect on nerve regeneration or functional recovery in the rodent nerve injury models studied. All assessments were made at time points suitable for detecting differences in nerve regeneration between groups. These findings suggest that administration of radiation to fields containing injured peripheral nerve is unlikely to adversely affect functional outcomes.