Researchers have found that botulinum toxin A injection is a safe and effective procedure for improving localized asymmetry in pediatric patients with facial paralysis, according to a study published in the journal JAMA Facial Plastic Surgery(Mar. 2015).
During this retrospective study, the investigators examined 18 patients ages four to 17 years who had been treated with botulinum toxin A injections from Jan. 2004 to Dec. 2012. The treatment was indicated for focal lip asymmetry, extensive hemifacial asymmetry, and focal synkinesis. The authors reported no complications from the therapy. The mean dynamic deviation before the injection was 3.5 (1.7) mm, whereas the mean dynamic deviation after the injection was 1.5 (0.8) mm. The mean deviation correction was evaluated at 61% (6%), which was statistically significant (p=0.04).
“[The purpose of the study] was to look at the outcomes and to answer the questions: does it work?; how well does it work?; are the patients happy with it?; and is it something that we should continue to offer? I think the answer to all those questions is, yes,” said Dr. Gregory H. Borschel, a plastic and reconstructive surgeon at The Hospital for Sick Children in Toronto and one of the study’s investigators. “It appears that [treating with botulinum toxin A] is worthwhile to do, and [the patients] seem to appreciate it.”
Dr. Borschel said that patients born with facial paralysis are mostly unilateral so they have a strong and weak side. Most often when they are younger they undergo surgery where a spar muscle from the leg is transported and attached to the nerves in the face to restore circulation. This allows the patient to raise the corner of their mouth and smile, but it does not allow them to move the lower lip. To show all teeth with a big smile, the lower lip has to raise, which these children cannot due to the paralysis.
This is where botulinum toxin comes in, said Dr. Borschel. “[It is an] opportunity to provide symmetry. It does not have to be perfect—we always strive for perfection, but we know we cannot really get there with some of these more severe cases,” he said.
“But what we can do is we can balance out the two sides. We can actually weaken the strong side to match the weak side.”
Botulinum toxin an adjunct to surgery
In severe cases the botulinum toxin is an adjunctive therapy to surgery, but for patients who develop less severe paralysis—possibly from a brain tumour, infection, or trauma—this therapy might be enough. The technique is also used for patients with focal synkinesis to soften unusual dimpling, according to Dr. Borschel.
The botulinum toxin can serve as a trial to determine if the patient likes the appearance, he noted. If the patient decides they want a more permanent effect, they can have another operation rather than returning every three to six months for another injection. This procedure, less complex than the spar muscle transplant, entails removing muscles from the stronger side.
The appeal of the botulinum toxin, according to Dr. Borschel, is that is a quick procedure—only taking a minute on average. “We start off small and do a test patch to see if they like it. If they want a longer duration of action, than we can up the dose,” he said.
“Giving the injection is pretty simple. We just do it in the clinic. We have them lie down and we say ‘we are going to give you a shot in the face, it is kind of like an immunization.’ We will use ice to provide a little bit of anesthesia often times and then give the injection,” he said. Following the treatment, the patient works with an occupational therapist to rehabilitate their facial movements by practicing smiling in front of a mirror.
Change is only a few millimetres
The shift is usually only about a few millimetres—up to about 5 mm—but that is noticeable because the human eye is very good at distinguishing between subtle differences between left and right.
Dr. Borschel said he has observed that his facial paralysis patients are affected by the asymmetry both functionally and aesthetically. Functional problems include difficulty with speech, such as making Bs, Ps, and M sounds. Also, their teeth can be affected because they cannot properly close their mouths. Most of these issues are corrected through surgery, but the botulinum toxin helps with the aesthetics. As well, it can improve the patient’s ability to communicate, because so much of communicating is achieved non-verbally.
While the technique is fairly novel, Dr. Borschel says some other centres are using it for pediatric and adult patients, and he believes it will become a more common practice.