Selective ansa cervicalis nerve transfer to the marginal mandibular nerve for lower lip reanimation : An anatomical study in cadavers and a case report

Background: Donor nerve options for lower lip reanimation are limited in patients undergoing oncological resection of the facial nerve. The ansa cervicalis nerve (ACN) is an advantageously situated donor with great potential but has not been examined in detail. In the current study, the anatomical technical feasibility of selective ACN to marginal mandibular nerve (MMN) transfer for restoration of lower lip tone and symmetry was explored. A clinical case is presented. Methods: Dissections were conducted in 21 hemifaces in non-embalmed human cadavers. The maximal harvestable length of ACN was measured and transfer to MMN was simulated. A 28-year-old male underwent ACN-MMN transfer after parotidectomy (carcinoma) and was evaluated 12 months post-operatively (modified Terzis' Lower Lip Grading Scale [25 observers] and photogrammetry). Results: The harvestable length of ACN was 100 & PLUSMN; 12 mm. A clinically significant anatomical variant ( "short ansa ") was present in 33% of cases (length: 37 & PLUSMN; 12 mm). Tensionless coaptation was possible in all cases only when using a modification of the surgical technique in "short ansa " cases (using an infrahyoid muscle nerve branch as an extension). The post-operative course of the clinical case was uneventful without complications, with improvement in tone, symmetry, and function at the lower lip at 12-month post-operative follow-up. Conclusions: Selective ACN-MMN nerve transfer is anatomically feasible in facial paralysis following oncological ablative procedures. It allows direct nerve coaptation without significant donor site morbidity. The clinical case showed good outcomes 12 months post-operatively. A strategy when encountering the "short ansa " anatomical variant in clinical cases is proposed.