Use of injectable agent requires knowledge of facial anatomy

Baltimore-Botulinum toxin type A (Botox, Allergan) and hyaluronic acid (Restylane, Medicin Aesthetics Holdings Inc.), injectable fillers used in facial rejuvenation, are gaining increasing popularity with patients and surgeons.

However, both have contraindications and carry the risk of potential complications. Achieving success when using these products depends on a detailed knowledge of the anatomy of the region being treated, according to Michael Grant, MD, PhD, FACS.

"These two compounds revolutionized the office-based practice of facial aesthetics. Both are easy to use with limited training and have little downside risk. They both have gained wide acceptance in our patient population, and patients are very satisfied with the effects of treatments," Dr. Grant said.

Botulinum toxin type A

The use of botulinum toxin type A is overwhelmingly safe, as demonstrated by the millions of applications performed worldwide, he noted. Recently, the agent was the subject of negative media reports as the result of botulinum toxin type A that was manufactured abroad and was injected by unlicensed physicians in south Florida. However, that product was unrelated to the product manufactured by Allergan, Dr. Grant pointed out.

Botulinum toxin type A works by inhibiting the release of neurotransmitters at the neuromuscular junction. The treatment effect becomes evident after 3 to 7 days, and lasts for 3 to 4 months in most patients.

"Ophthalmologists were the first to begin using botulinum toxin type A to treat strabismus, blepharospasm, and nystagmus. Most recently, it has been shown to be effective in the treatment of migraine," said Dr. Grant, assistant professor of ophthalmology and plastic surgery, oculoplastics division, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore.

What really spurred the increased use and popularity of botulinum toxin type A was the FDA approval of the cosmetic indication in the spring of 2002. Data from the American Society of Plastic Surgeons showed that about 2 million botulinum toxin type A cosmetic treatments had been performed by summer 2004, which constituted 20% of all office-based procedures and was the most common procedure performed.

"A plus for surgeons is that the use of botulinum toxin type A is a patient's frequent entry point into the practice for other cosmetic procedures," he pointed out.

The only FDA-approved cosmetic indication for botulinum toxin type A is the treatment of glabellar lines. It is, however, injected in other periocular locations as well as the mid and lower face, according to Dr. Grant.

"In my experience, the frequency of unwanted outcomes can increase as botulinum toxin type A is injected lower on the face, unless the surgeon is familiar with the anatomy in this region, and can result in asymmetric smiles, or oral incompetence, which can last for 1 or 2 weeks. Ophthalmologists have more than enough knowledge of the eye and periocular region to learn how to inject botulinum toxin type A successfully," he said.

The goal of injecting botulinum toxin type A, he explained, is not just to treat a wrinkle but to reposition the soft tissue by selectively deinnervating the muscle or muscle groups to influence a result. This implies that the clinician has knowledge of the anatomy.

"The frontalis muscle is the main elevator of the brow and the lateral orbicularis muscle and corrugators are the main depressors of the brow. Knowing that anatomy and the relative positions of the muscles allow repositioning of the brow by deinnervating the lateral orbicular and corrugators," Dr. Grant explained.

The corrugator and procerus muscles can be treated in the periorbital region to eliminate frown lines. Deep forehead muscles may benefit from treatment of the frontalis muscle. Lateral canthal wrinkles (smile muscles) can be addressed by treating the lateral orbicularis muscle. Wrinkles over the dorsum of the nose (bunny lines) can be improved by treating the nasalis muscle.

"My approach when examining a patient is to identify the location of the wrinkles and any asymmetry in the lines or in the brow position. I then have to determine if the involved muscles are superficial or deep and then the manner in which I will inject the botulinum toxin type A to achieve the desired result," Dr. Grant said. "Any asymmetry is discussed with the patient preoperatively; many do not realize that there is asymmetry.