J Endocr Surg.  2019 Dec;19(4):144-150. 10.16956/jes.2019.19.4.144.

What You Need to Know about Mental Nerve Surgical Anatomy for Transoral Thyroidectomy

• Pino A
• Parafioriti A
• Caruso E
• De Pasquale M
• Del Rio P
• Calò PG
• Dionigi G
• Stagno d'Alcontres F

• KMID: 2466240
• DOI: http://doi.org/10.16956/jes.2019.19.4.144

Abstract

No abstract available.

MeSH Terms

Thyroidectomy*

Figure

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  Fig. 1 MN is a branch of the posterior trunk of the inferior alveolar nerve, which is itself a branch of the mandibular division of the trigeminal nerve. The MN emerges at the mental foramen in the mandible, and divides beneath the depressor anguli oris muscle into 3 branches: one descends to the skin of the chin, 2 ascend to the skin and mucous membrane of the lower lip. These branches communicate freely with the facial nerve. MN = mental nerve.

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  Fig. 2 The mental foramen may be oval or round and is usually located apical to the second mandibular premolar or between apices of the premolars. However, its location can vary from the mandibular canine to the first molar. Very few variants of this nerve have been described in literature.

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  Fig. 3 mental nerve is a sensory nerve which provides sensation to the front of the chin and lower lip as well as the labial gingivae of the mandibular anterior teeth and the premolars.

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  Fig. 4 Landmarks for MN identification. (A) MN origin and foramen is 2 cm below the ipsilateral labial commissure, a finger nail above the jaw; (B) the nerve is 2.5 cm lateral to an imaginary median line of the face; (C) in the intra-oral perspective, the MN originates between the 3rd and 4th tooth. MN = mental nerve.

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  Fig. 5 The dissection of the MN on cadaver allowed to highlight the course of the MN and its ramifications. The MN has a medial curvilinear course. MN soon branches out. The areas highlighted in green are zones with absence or less concentration of peripheral branches of the MN. A vestibular incision in these areas appears to be safe and prevents MN injury. Conventionally, the central incision is 1–2 cm in length and is placed beyond the cranial aspect of the buccal-mandibular frenulum, while 2 lateral 5 mm incisions are made at the most lateral-anterior aspect of the oral commissure in the mucosal border to avoid MN injury and instrument collision. It should be noted that a too inferior median incision, too close to the gingiva (red area) can interfere with the endoscopic instruments and furthermore create adhesions/sinechie with the gingival sulcus or lesion of the inferior labial frenulum. MN = mental nerve. *MN branches.

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