Effect of Motor versus Sensory Nerve Autografts on Regeneration and Functional Outcomes of Rat Facial Nerve Reconstruction

Abstract

Cranial nerve injury is disabling for patients, and facial nerve injury is particularly debilitating due to combined functional impairment and disfigurement. The most widely accepted approaches for reconstructing nerve gap injuries involve using sensory nerve grafts to bridge the nerve defect. Prior work on preferential motor reinnervation suggests, however, that motor pathways may preferentially support motoneuron regeneration after nerve injury. The effect of motor versus sensory nerve grafting after facial nerve injury has not been previously investigated. Insights into outcomes of motor versus sensory grafting may improve understanding and clinical treatment of facial nerve paralysis, mitigating facial asymmetry, aberrant reinnervation, and synkinesis. This study examined motor versus sensory grafting of the facial nerve to investigate effect of pathway on regeneration across a 5-mm rodent facial nerve defect. We enrolled 18 rats in 3 cohorts (motor, sensory, and defect) and recorded outcome measures including fiber count/nerve density, muscle endplate reinnervation, compound muscle action potential, and functional whisker twitch analysis. Outcomes were similar for motor versus sensory groups, suggesting similar ability of sensory and motor grafts to support regeneration in a clinically relevant model of facial nerve injury.

Schwann Cell Role in Selectivity of Nerve Regeneration

“…The phenotypic memory of the SCs after denervation might play a role in PMR, since graft modality used to repair a nerve resection influences the outcome of axonal regeneration. While some studies could not find improved motor regeneration when the femoral or the facial nerve were repaired with modality-matched grafts [ 68 , 69 ], others found that motor axons from the sciatic and tibial nerve regenerated better through a ventral root or a motor nerve than through a sensory graft [ 57 , 70 , 71 ]. The selective effect may be partially sustained in predegenerated grafts.…”

Facial Nerve Reconstruction with Free Vascularized Composite Nerve Flap from Intrapetrous Portion to Terminal Branches—Case Report

“…Thoracodorsal nerve or portions of the femoral nerve have been investigated as donor areas for NG. 18 19 20 Motor nerves as VNT have also been described either alone or as a part of composite free tissue transfers for facial defects. 21 22 …”

Deletion of CD38 and supplementation of NAD+ attenuate axon degeneration in a mouse facial nerve axotomy model

“…Also, when the nerve gap is larger than 5-mm, nerve interposition or "cable graft" procedures are commonly performed. However, the recovery of the transected or resected nerve after reconstruction of the nerve defect is not satisfactory 53 . Thus, the treatment of functional recovery after facial nerve axotomy is still a major problem.…”