Human cadaveric model for studying the preservation of mental nerve during transoral endoscopic thyroidectomy

Purpose Mental nerve (MN) injury can be caused by transoral endoscopic thyroidectomy vestibular approach (TOETVA). The purpose of this experimental study was to determine the location and distribution pattern of MN structures in relation to oral vestibular incisions. Methods Ten cadaver specimens were included, yielding a total of 20 MNs. The difference between standard 10-mm TOETVA median incision and modified incision (i.e. lower and perpendicular) was compared. Results All 20 MNs were successfully dissected and presented as bifid (100%), lateral toward medial direction. The branches of MNs were equally distributed into both right and left sides. Standard lateral 5-mm vestibular incisions did not determine any division of MN branches. Two left MNs (25%) and one right MN (12.5%) were injured by standard median vestibular incision. Using a more inferiorly positioned and a vertical median incision, the integrity of MN branches was preserved. Conclusions Standard lateral 5-mm vestibular incisions are safe for determining MN integrity. The 10-mm median vestibular incision divided the medial ramifications of MN at a rate of 12–25%. These may result in MN ipsilateral or bilateral paralysis. Hence, it is recommended to locate the median incision more inferiorly or vertically.