Mental nerve preservation in transoral endoscopic thyroidectomy: anatomy, sensory outcomes, and technical considerations

Transoral endoscopic thyroidectomy vestibular approach eliminates the visible cervical scar but introduces a unique risk of mental nerve injury. This review synthesizes the anatomical, technical, and clinical evidence regarding chin and lower-lip sensory changes after transoral thyroidectomy, identifies current knowledge gaps, and discusses strategies for nerve preservation. Anatomical studies using modified Sihler’s staining in cadavers have delineated a trapezoidal midline region in the oral vestibule that appears to be largely free of mental nerve branches, providing a rationale for port placement, though individual anatomical variation precludes designation of any zone as universally safe. Reported rates of postoperative mental nerve disturbance vary widely (0%-81%), largely because of inconsistent definitions and assessment methods. A recent prospective study using area-based monofilament mapping in 37 transoral and 40 conventional thyroidectomy patients demonstrated universal early sensory deficits in the transoral group that diminished progressively, with a statistically significant reduction in affected area over 2 months. Gasless single-incision modifications that confine vestibular dissection to the defined safety zone may further reduce nerve traction and CO<sub>2</sub>-related risks. Nevertheless, the existing evidence base remains small and originates from a limited number of groups; larger multicenter studies with standardized outcome measures are needed. Preoperative counseling should address expected transient numbness, the typical recovery trajectory, and the favorable cosmetic benefit-to-risk profile.