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Page 10 of 12 Favre et al. Plast Aesthet Res 2020;7:71 I http://dx.doi.org/10.20517/2347-9264.2020.149

Figure 8. Injection sites above the elevated eyebrow or below the depressed eyebrow in brow asymmetry from brow ptosis

and keloids by BoNT is currently not completely understood, several studies have pointed to a potential
expansion the off-label use of BoNT-A for pathologic scarring.

COMPLICATIONS
Although there are specific complications and contraindications with usage of BoNT for specific muscle
groups that were discussed above, there are general complications to be aware of regardless of where the
injection is located. Locally, the complications are most commonly related to the injection site. These
complications include development of pain, erythema, ecchymosis, or hematoma at the site of injection. It
is often helpful to use local anesthetics and inject the neurotoxin at a slower rate to avoid these injection
site complications. It is important to inform your patients that ecchymosis is common and can take up
[32]
to two weeks to resolve . As discussed in detail above, another common side effect is diffusion of the
neurotoxin to adjacent muscle groups resulting in paralysis of those muscle groups and unwanted aesthetic
as well as functional side effects. Care must be taken to ensure the toxin is injected directly into the desired
[33]
muscle .
Some less common complications of BoNT injection include development of a mild and self-resolving
headache with facial injections, paresthesia in the area of the injection site caused by local nerve trauma,
[32]
and vasovagal episodes associated with anxiety during the injection procedure . It is important to be
aware of these side effects in order to avoid further complications. Finally, two extremely rare complications
to note are the formation of antibodies against the BoNT, which would make the treatment ineffective,
and the possible immediate allergic reactions to the toxin, which would present with itching, swelling, and
[34]
possible anaphylaxis . For the formation of antibodies, medications that inhibit neuromuscular signaling
can be used to increase the toxin’s effect by offsetting the antibody reaction. In the case of an allergic
reaction, standard allergy protocol is recommended, but diphenhydramine is not recommended due to is
anticholinergic effects.

CONCLUSION
BoNT has been proven to be safe and efficacious for many clinical indications in the field of facial plastic
surgery. The use of BoNT for rhytids of the face has become one of the most common non-invasive
procedures in facial plastic surgery with an extremely high patient satisfaction rate. In addition to the
FDA approved usage of BoNT for rhytids, off-label uses, such as those described above, are becoming