Requirement of the Preservation of Mental Nerve During the Transfer of Depressor Anguli Oris Composite Flap

Abstract

Objectives: Reconstruction of wide lower lip defects is still a challenging subject in terms of obtaining functional and aesthetically acceptable results. Lower lip reconstruction with depressor anguli oris muscle was first described by Tobin in 1983. Since the sensory innervation of this composite muscle flap is provided by the mental nerve, it has been advocated that the mental nerve should be preserve during flap elevation. However, no further study has been conducted about this subject since then.

Methods: Sixteen patients with lower lip mass have undergone excisional biopsy. The resultant defects were higher than 30% of the total lower lip. All the defects were reconstructed with Depressor anguli oris composite flaps. In 9 of the patients, the mental nerve was preserved and included to the flap, while in remaining patients it was sacrificed. The results were evaluated in terms of sensation, function, and aesthetic appearance.

Results: In unilaterally reconstructed cases, the results regarding sensation and general complications were similar. However, in bilaterally reconstructed cases, especially where the mental nerve was preserved, the limited arc of rotation has resulted in functional complications, such as whistle deformity in the midline and drooling.

Conclusion: The mental nerve does not just limit the arc of rotation of the Depressör anguli oris composite flap but also remains as a potential route for metastasis via perineural invasion. Preservation and inclusion of the mental nerve during reconstruction with Depressor anguli oris flap do not provide any superior outcome; on the contrary, these results in various unfavorable events make this flap a poor option. The skin and mucosa of the DAO flap are innervated by the buccal branch of the trigeminal nerve; thus, the mental nerve should not be preserved during surgery.

Keywords: Depressor anguli oris; lower lip; mental nerve.

Figure 1

Rotation arc of the flap in case of preservation or resection of the mental nerve. Black arrow, Marginal mandibular nerve; Green arrow. Preserved mental nerve; Yellow arrow: The cut point of the mental nerve.

Figure 2

Patient no 16. (a, b, c) perop, (d) postop 2^nd month, (e, f) postop 9^th month.

Figure 3

Patient no 13, (a) preop, (b) perop, (c) postop 1^st week, (d, e) postop 8^th month.

Figure 4

Patient no14, (a) perop, (b) postop two weeks, (c, d) postop five months.

Figure 5

Anesthetized area innervated by mental nerve.