THE ISOLATED PARESIS OF THE MARGINAL MANDIBULAR BRANCH OF THE FACIAL-NERVE - CLINICAL-APPEARANCE, CAUSES, DIAGNOSIS, AND THERAPY - AN OVERVIEW

Background: Disorders of lower lip in facial expression are mostly cau sed by functional impairment of the marginal mandibular branch of the facial nerve. In a typical case, active exposure of the incisors of th e mandible is not possible and the lip appears distorted towards the h ealthy side. The most frequent cause of a lesion of the marginal mandi bular branch is iatrogenic injury during operations in the mandibular or parotid region. Differential diagnosis: Functional disorders of the platysma, congenital hypoplasia or aplasia of the lower lip muscles, and defective healing following facial palsy may lead to a similar dis order which, however, must be differentiated from an isolated paralysi s of the marginal mandibular branch. Treatment: In addition to inactiv ation of the nerve branch on the opposite side, several surgical proce dures have been described to achieve not only aesthetic, but also func tional rehabilitation of lower lip expression. The present review give s an overview on the causes, clinical appearance, diagnosis, different ial diagnosis, and therapy of unilateral isolated paresis of the margi nal mandibular branch of the facial nerve.