Congenital Unilateral Hypoplasia of the Orbicularis Oris Muscle: A Rare Cause of Congenital Unilateral Upper Lip Palsy

Asymmetric facial appearance may originate from abnormalities of facial musculature or facial innervation. Congenital absence or hypoplasia of facial muscles has not been known except for the depressor anguli oris muscle. Even, congenital unilateral hypoplasia of the orbicularis oris muscle cause of unilateral upper lip palsy has not been reported in the literature up to day. In this report, we present a patient with congenital unilateral upper lip palsy although the facial nerve was normal.