Fortunately, botulinum toxins are rarely associated with side effects such as allergic reactions. This article will focus on some of the potential complications associated with the most commonly injected areas.
Glabella
The dreaded complication of glabellar injections is eyelid ptosis. This happens in less than 2 percent of individuals. This percentage is largely reduced when proper technique is used. One proposed etiology of toxin induced blepharoptosis is the neurotoxin diffusing down the supraorbital and/or supratrochlear neurovascular bundles. When injecting the corrugators, it is important, therefore, to protect the orbital rim with the non-dominant hand while pinching the muscle.
Crow’s Feet
Injections into the orbicularis oculi muscle can weaken the blink reflex and exacerbate dry eyes. Take caution injecting this area in patients with pre-existing ocular surface issues and keratitis sicca.
Other potential complications of crow’s feet injections are very rare, including weakening untargeted muscles, especially when down near the cheek area. If the needle is placed too deep, one could potentially inject the zygomaticus. Stay very superficial, as if giving a tuberculin skin test, to avoid this complication. If the injection is given too close to the lateral canthus, there is a small risk of seepage into the lateral rectus muscle, which would lead to disabling diplopia.
Frontalis
The most common complaint associated with frontalis injections is the “droopy” or “heavy” eyelid secondary to brow ptosis, which must be differentiated from true blepharoptosis. By weakening the elevating action of the frontalis, you get a net depression.
To avoid brow ptosis, inject conservative amounts of toxin (2 to 2.5 units of Botox or Xeomin and 5 to 6 units of Dysport per injection site), stay at or above midline and always combine frontalis injections with glabellar injections to get the net lift from weakening the corrugators and procerus. If the frontalis is under-injected in certain areas, parts of the muscle will still have action while the surrounding muscle will be paralyzed, resulting in the “spock” brow. This issue can easily be treated with a small dose of toxin to the area that is still moving.