For marionette lines, it is recommended that botulinum toxin should be injected into the lower part of the depressor anguli oris (DAO) to minimize the risk of unwanted spread to other muscles responsible for movement of the corners of the mouth. Similarly, the mentalis hyperactivity in Asians is secondary to congenital, bony retrusion of the chin. The cobblestone-looking chin can be improved by few amount of botulinum toxin.

Bilateral injection of the masseter muscles decreases their prominence and produces tapering of the lower face. Repeated, high-dose injections over several years can result in chronic muscular atrophy. According to a prospective study by Dr. Chung-Chih Yu et al. from Taiwan, a decrease in masseteric volume typically starts to become apparent 2 weeks after injection of 120 U abobotulinumtoxin A on each masseteric muscle in 6 injection spots. The effect continues to develop over the following 1 to 3 months. The peak of muscle atrophy is usually reached by 3 months post injection. Muscle volume is usually restored to some extent at 6 months and may reach its pretreatment state by 10 to 12 months after injection. Bite forces decreased from the first day after injection, but started to recover during the third week and were normal 3 months after injection. Three-dimensional CT evaluation showed a statistically significant mean 30% masseter reduction, but without change in the volume of other masticating muscles.

 

HELIOSⅡ/LOTUSⅡ/HYPERION – Manufacturer: LASEROPTEK(www.laseroptek.com)

 

It is well known that appropriate candidates for treatment should be patients with significant masseteric muscle volume, rather than bony prominence of the mandibular angle. However, a previous animal study by Dr. Chi-Yang Tsai et al. from Taiwan showed that after localized masseter muscle atrophy induced by onabotulinumtoxin A injection, alterations of craniofacial bone growth and development were also seen. Physiologically, muscles have a contraction effect on the periosteum. By pulling away from the periosteum, bone deposition occurs. They found the mandibular plane angle, ramus height, and total mandibular length decreased after onabotulinumtoxin A injection to reduce the amount of masseter muscle contractions. Their study results proved the functional matrix theory that soft tissues regulate bone growth. Therefore, it is possible to change the shape and angle of the mandibles by appropriate repeated, high-dose, long-term botulinum toxin injections into masseter muscle.

Some anecdotal observations as well as my personal experience showed that Asians are less likely than Caucasians to develop platysmal bands. “Nefertiti neck lift” by injecting the specific portion of platysma is popular in Taiwan. This method is considered an inexpensive method to replace the more expansive invasive surgical face lift, thread lifting, or non-invasive radiofrequency and high intensity focused ultrasound (HIFU).

Body shaping with botulinum toxin is increasing in Taiwan, but it is not as common as its application on face. People here tend to have short legs with thick calves. 60 to 100 U onabotulinumtoxin A is typically injected into the head of each gastrocnemius through multiple injection points. Mild temporary muscular weakness following treatment may manifest as difficulty in climbing stairs.

Other than previous implication, botulinum toxin can also be injected into all of the face intradermally. Initially designed as a face-lifting method, some reports showed an increased collagen synthesis effect after intradermal injection of botulinum toxin to the whole face. We previously described a report from Dr. Shao-Ping Chang et al. in Taiwan. By reconstituting 100 U onabotulinumtoxin A with 10 mL of sterile, preservative-free saline, a total dose of 20 to 25 U onabotulinumtoxin A was injected for each person by 0.02 mL (0.2 U) per spot intradermally to the mid and lower face in a 1-cm interval through a 30-guage needle. A statistical significant result in wrinkles reduction and soothing effect was found 4 weeks after injection, and lasted for more than 8 weeks. However, there was no significant face-lifting effect, even though a slight neocollagen synthesis was demonstrated histologically. The wrinkles smoothing effect was thought to be associated with the blockage of botulinum toxin on the muscle fiber rather than the increment of collagen synthesis. From an evidence-based perspective, large, placebo-controlled trials are required to evaluate the exact efficacy of intradermal botulinum toxin injection. The physicians should also be very careful to avoid “mask-like” face effect when injecting too many points on the whole face.

 

The Future

Injection with botulinum toxin has become the most popular cosmetic procedure, and additional aesthetic applications have been continuously discovered throughout the years. When planning treatment with botulinum toxin, it must be understood that anatomic and cultural differences exist not only between Asians and Caucasians, but also among individuals. To select the most appropriate kind and dosage of botulinum toxin for different patients may be difficult and confusing. It is therefore hoped that the more delicate injection techniques and consensus for various ethnic groups will be recommended in the near future.

 

-To be continued-