Characteristics of Nerve Injury, Regeneration, and Vocal Fold Movement After Recurrent Laryngeal Nerve Electrocautery Injury.

OBJECTIVE

To investigate the temporal patterns of regeneration and functional recovery following a unilateral recurrent laryngeal nerve (URLN) electrocautery injury.

METHODS

Unilateral recurrent laryngeal nerve（RLN） injury rabbit models (n = 12) were established. At 2, 4, 8, and 12 weeks post-injury, RLN and neuromuscular junction regeneration were evaluated via transmission electron microscopy and immunofluorescence. Thyroarytenoid muscle histopathology was assessed by hematoxylin and eosin staining, and vocal fold (VF) movement was quantified via laryngoscopy. Correlation between neuroelectrophysiological changes and VF motion was analyzed in eight patients with RLN electrocautery injuries.

RESULTS

At 2 weeks, myelin sheaths and synaptic membranes showed extensive disintegration. The single muscle fiber diameter (SMFD) decreased to 56.16%, the muscle fiber area ratio (MFAR) decreased to 40.35%, and the motion range ratio (MRR) decreased to 12.2%. At 4 weeks, the myelin lamellae continued to disintegrate with a small amount of regeneration. Regeneration of the presynaptic membrane (more than the postsynaptic membrane) began. MFAR was 46.86%, and MRR was 77.9%. At 8 weeks, the density of myelinated axon (DMA) peaked, but the axons and myelin sheath remained thin and immature. Postsynaptic membrane regeneration was significant, with partial overlap by the presynaptic membrane. MFAR rose to 58.59%, and MRR recovered to 96.9%. At 12 weeks, myelin sheaths thickened and matured despite a drop in DMA. Synaptic membrane number and morphology were normalized. SMFD and MFAR neared normal levels at 94.52% and 91.57%, respectively, and MRR recovered fully. 77.8% of patients exhibited partial or complete VF movement recovery.

CONCLUSION

Despite causing initial injury, electrocautery may still permit sufficient axonal regeneration and subsequent muscle reinnervation to enable partial or complete recovery of VF movement.