Neuromodulator for the Treatment of Congenital Unilateral Lower Lip Palsy

Congenital unilateral lower lip palsy is an infrequently encountered condition that manifests as lower lip asymmetry during smiling, laughing, and crying. Treatment options are not well characterized.

The authors present the case of a 51-year-old woman who was referred for surgical intervention for facial paralysis. Physical examination demonstrated a symmetric face at rest that became asymmetric when smiling. The asymmetry, evident by inappropriate inferior displacement of the lower lip, was secondary to unilateral contraction and presence of the depressor labii inferioris. The depressor anguli oris was symmetric bilaterally. Her presentation was consistent with congenital unilateral lower lip palsy.

Lidocaine was injected into the depressor labii inferioris on the side of the face that demonstrated unilateral presence and contraction. This resulted in symmetry of the smile and lower lip without untoward effect. Onabotulinum toxin A was thereafter injected into the depressor labii inferioris. In-office treatment with botulinum toxin injection resulted in a 4-month improvement in smile symmetry.

Chemodenervation is a safe and minimally invasive method to improve smile symmetry and lower lip position in cases of congenital unilateral lower lip palsy.