PracticalDermatology

Marginal mandibular nerve paresis is a rare complication seen following submental deoxycholate injections. We present a novel way to address and mitigate this issue much more quickly than past medical literature estimates to the patient’s satisfaction by optimizing the clinical nuance of two different FDA-approved neuromodulators.

The potential problem

Kybella® (Deoxycholate) remains the only U.S. Food and Drug Administration-approved injectable treatment for the reduction of submental fat. Mandibular nerve paresis may result in a temporary asymmetric smile and/or facial muscle weakness that can last for a median of 6 weeks. It occurs if the product spreads to the nearby marginal mandibular nerve near the jawline. A study in fresh human cadavers showed that deoxycholic acid (10 mg/ml) directly temporarily damages the marginal mandibular nerve myelin sheath by a lipid-dissolving de-myelination, which is eventually regenerated, resulting in the nerve injury.¹ In one study of 100 patients who underwent 152 Kybella treatment sessions in a private practice setting, two patients experienced marginal mandibular nerve paralysis.² This side effect was also seen in four percent of patients in Kybella’s pivotal trials.³

Use the interactive slider below to compare days 1 and 10:

Before treating marginal mandibular nerve paresis and 10 days after.
Images courtesy of S. Manjula Jegasothy MD

Mandibular nerve paresis fully resolved in 10 days.
Images courtesy of S. Manjula Jegasothy MD

Day 1, Day 5, and 2 months following treatment of marginal mandibular nerve paresis.
Images courtesy of S. Manjula Jegasothy MD

The solution

If a patient does experience this complication, I recommend addressing it immediately. Since injury to the mandibular nerve causes ipsilateral depressor anguli oris (DAO) and depressor labii inferioris (DLI) paresis, I “corrected” this lower facial asymmetry by injecting Dysport® (abobotulinumtoxinA) and Botox® Cosmetic (OnabotulinumtoxinA) simultaneously into the contralateral DAO & DLI muscles. I used small amounts (~3 Dysport units total) of Dypsort in the DLI muscles because of its better diffusion and faster onset of action. I injected Botox Cosmetic into the DAO in slightly larger amounts (~ 2 Botox units total) to precisely maintain the effect in this larger facial muscle for the full 6 weeks as the contralateral marginal mandibular nerve/DAO/DLI complex recovers.

The patient’s smile is even in 10 days, as opposed to industry-standard 44 days prior to this. Both sides of the mouth then come down evenly over the following two to three months.

This article is based on a presentation from Cosmetic Surgery Forum (CSF) 2021. Visit CosmeticSurgeryForum.com for information about future meetings.

1. Blandford, AD, et al. Deoxycholic Acid and the Marginal Mandibular Nerve: A Cadaver Study.”Aesthetic Plastic Surgery, October 2018:1394-1398.

2. Shridharani, SM. Early Experience in 100 Consecutive Patients with Injection Adipocytolysis for neck Contouring with ATX-101 (Deoxycholic Acid). Dermatologic Surgery, July 2017:950-958.

3. Allergan Inc. “Safety Profile.” Kybella.com, https://hcp.mykybella.com/safety-profile.