Case 3 Discussion

1) What nerve and muscle is injured (please designate left or right)?

The Right Mandibular Nerve is injured. Innervated by the Mandibular Nerve is the Depressor Anguli Oris and Depressor Labii Inferioris Muscles, which normally depress the lip inferior and lateral. The unopposed activation of the Left Depressor Muscles is causing the patient to have an assymetrical smile to the left.

2) What therapy would you offer to improve this problem?

Botox to the Left Depressor Muscles (primarily the DAO) is a therapeutic option. The patient is able to smile symmerically because the Levator Muscles of the Mouth, innervated by the Buccal Nerve, are unaffected. After Botox to the Left DAO, there is bilateral inactivation of the Depressor Muscles, resulting in a symmetrical smile.

Below are the before and after procedure results.


After Botox

*actual patient case of Dr. Liu©


3) What is your skin landmark and dissection plane to avoid this type of surgical complication?

Dissection superficial to the Superficial Muscular Aponeurotic System is typically a safe dissection plane. The anterior border of the Masseter Muscle at the rim of the Mandible is an approximation of the nerve location.

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