Refinements in cervical-to-marginal mandibular nerve transfers for late and chronic facial palsy cases: A pilot study

Marginal mandibular nerve palsy is among the most common facial nerve iatrogenic injuries and has significant functional and aesthetic consequences. In a case series of four patients (n = 4) with iatrogenic and acquired marginal mandibular nerve injuries, we performed a cervical branch facial nerve (VII_c) fascicular transfer to the marginal mandibular nerve (VII_m) for late and chronic facial palsies. Pre-and post-op videos were then analysed to determine the return lower lip depression, using the Terzis lower lip score and smile index was used for objective assessment. Overall, 75% of the cases were secondary to iatrogenic injuries viz., two post-neck dissections and one post-submandibular gland excision, while one case had non-flaccid facial paresis. In all four cases, the depressor labii inferioris (DLI) function returned during open mouth smile activation. Cervical-to-marginal mandibular (VIIc-VIIm) nerve transfers are indicated in acute VIIm injuries (<18 months post-onset) and in long-term cases of DLI paresis. However, it is not useful in patients with complete DLI paralysis, for which conventional methods are better suited. However, in the future, it may be considered for the management of congenital unilateral lower lip palsies, wherein the DLI is paretic.