Requirement of the protection of mental nerve during the adaptation of depressor anguli oris composite flap

Abstract

T he lips, with their unique anatomical structures, form important esthetic units on the lower 1/3 of the face. [1] Lips are very important in terms of motor and sensory functions. Defects in the lips developed for any reason should be repaired in such a way to preserve the functions of nutrition, respiration, speech, facial expressions, kissing, blowing and self-expression.The most common cause of defects in lips is defects that occur after cancer surgery. [2] Once the lower lip cancers have reached a certain size, it is not possible to remove the tumor and to repair the defect. In such cases, regional or distant flaps are used for reconstruction of the defect. The most appropriate method for repair is the use of local flaps when there is a defect that does not exceed the mental fold 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.