What is Botox® and why is it used for facial paralysis?
Botox® (also known as botulinum toxin) is a well-studied medication with a large number of applications. It is most commonly associated with preventing wrinkles in the cosmetic world. Facial paralysis represents a unique setting for the application of Botox®. It is a purified form of a naturally-occurring toxin from bacteria (Clostridium botulinum) that is responsible for botulism. The mechanism of action is by binding to receptors at the junction between nerves and muscles (neuromuscular junction) and preventing nerve stimulation from entering muscles.
In essence, it induces paralysis where you inject it. Sometimes in the setting of facial paralysis, there may be only partial paralysis affecting a portion of the face. This can cause asymmetry that can be unfavorable for many patients. This can also occur after smile reanimation or other types of facial paralysis reconstruction where correcting one deficiency may unmask an asymmetry somewhere else on the face. Botox® injection is aimed at correcting asymmetry by re-establishing balance from unopposed muscle contraction.
Similarly, it can be used in synkinesis to disrupt unwanted facial contractions. More specifically, Botulinum toxin is used early on in the treatment of synkinesis by injecting directly into the muscles causing twitching on the paralyzed side of the face. This allows for the overactive muscles to settle and can indirectly limit stimulation through the synkinetic pathways. By doing so, symmetry and function of facial muscles is restored early.
How is Botulinum Toxin injection performed for facial paralysis?
The technique of injecting Botox® is well-described. Botulinum toxin is injected by the unit into the targeted muscles beneath the skin with a thin needle. This is done most commonly without the need for anesthesia, but topical anesthetic cream (EMLA) can be applied as well for comfort in children. Botox® can also be injected during surgery for other areas. The treatment plan is tailored prior to injection. One of the most common areas of injection is into the lower lip depressor muscles. This is done to re-establish symmetry of the lower lip and to prevent excessive contraction on the non-paralyzed side of the face. Similarly, the forehead on the non-paralyzed side of the face can be injected to restore symmetry, similar to cosmetic applications. Botox® can also be applied into muscle groups that are overactive in the setting of synkinesis. Refer to the Synkinesis section for details.
How long does Botox® last for facial paralysis?
The duration of effect for Botox® is between 3-6 months. It will then need to be repeated to maintain the desired effect. Because of its temporary nature, Botox® is sometimes used to visualize the effect of symmetry correction procedures prior to performing the actual surgery.
What are the risks and complications of Botox® injection for facial paralysis?
Botox® has minimal risks and has been used widely for various applications. Allergic reaction, bruising, lack of effect, and migration to adjacent muscle groups have been known to occur. Depending upon the area, this can mean paralysis of unintended muscles. For example, Botox® injected into the forehead may result in eyelid droop. Nonetheless, the risks and complications are rare and quite minimal. Dr. Panossian is an expert in the use of Botox® and other interventions for facial paralysis. Botox® injections are most often performed comfortably in the office with no downtime.