Myectomy or removal of functioning muscle can be a relatively simple yet effective method for improving facial symmetry and achieving a refined result. Myectomy is frequently used to help balance an asymmetric lower lip.

During a full smile, the muscles of the upper lip retract upward partially exposing the top teeth. At the same time the muscles of the lower lip work in the opposite direction to produce slight depression of the lower lip partially reveal the bottom teeth. It is the loss of lip depression that is frequently responsible for subtle smile imbalances.

The marginal mandibular branch of the facial nerve is responsible for controlling the muscles of the lower lip and sometimes is damaged during cosmetic or tumor surgery. Alternately, it may fail to develop in utero or be damaged during the birth process.
Marginal Mandibular Branch

Following a partial recovery from unilateral facial paralysis the function of the unaffected side of the face may appear hyperactive. Selective weakening of muscles on the overactive appearing (unaffected) side of the face can help restore more balanced facial motion. Additionally, the weak, stretched out facial muscles on the previously paralyzed side of the face can be shortened or tightened in an effort to enhance symmetry.

Technique

The effects of surgery can be simulated in the clinic by injecting local anesthesia into the desired muscle group producing a temporary weakness that lasts one to two hours. Similarly a more prolonged trial can be obtained by injecting Botox that has a comparable effect of 3 to 6 months in duration.

If the individual is satisfied with the improvement in symmetry produced by injection of local anesthesia or Botox then the effect can be made permanent during a short outpatient procedure.

Surgery to balance the lower lip is performed through incisions inside the mouth avoiding the creation of external scars. Segments of the lip depressor muscles are removed on the normal side (myectomy) to produce a more harmonious smile.