Depressor labii inferioris (DLI) excision
The depressor labii inferioris (DLI) muscles move the lower lip downward to expose the bottom teeth during smiling. Often, patients with facial palsy have too much activity in this muscle on the unaffected side of their face. This hyperactivity creates an asymmetry while patients smile, since the unaffected side lower lip moves down but the other side does not. By weakening the healthy DLI muscle, we create a more symmetric smile.
One option is to give the healthy side muscle an injection of Botox to weaken it. When this maneuver works, we can either repeat it every 3-6 months indefinitely (or until spontaneous recovery of the weak side), or we can divide some of the muscle fibers on the healthy side to provide permanent balance. Resection of this muscle is very straightforward in the office setting, and there is almost no downside. The entire procedure takes 15-20 minutes. After the procedure, patients can eat and drink normally after the numbing medication wears off (about an hour). The final effect of the DLI resection can be appreciated after a few weeks. There is no visible scarring. Occasionally patients experience minor temporary lip numbness, or do not get as much weakening as desired, in which case it can be safely repeated.