Chapter 4 Botulinum Toxin
Summary
Introduction
Eight neurotoxins are secreted by Clostridium botulinum.1 Type A is a fully sequenced 1295 amino acid chain surrounded by other hemagglutinin and nontoxic nonhemagglutinin proteins for stability.
Dr Alan Scott, an ophthalmologist, pioneered the use of botulinum toxin type A in humans. His first publication, detailing the toxin’s effect on Rhesus monkeys, appeared in 1973.2 He first injected the toxin into humans in 1977 (Scott AB, personal communication). His first publication concerning the injection of the toxin into humans was published in 1980.3
For years, the toxin was an effective, though seldom used medication, limited to the field of investigational ophthalmology. Its primary uses were for blepharospasm and strabismus. There were rare anecdotal reports of its use for wrinkle reduction (Wyshynski PE, personal communication).4 The first comprehensive report detailing its cosmetic usefulness was published by the Carruthers, an ophthalmologist/dermatologist team, in 1992.5
Most patients have an initial excellent response for the first 3.5-4 months, with diminishing returns thereafter as the muscle regains its strength. However, when carefully scrutinized, it typically takes 6-7 months for all of the clinical effects to fade. As patients continue to have the toxin injected on a regular basis over 2 years, most begin to have an increased duration of action.6 Initially, recovery appears to be facilitated by neurite sprouting as early as 8 weeks after injection. It also appears that the initially blocked nerve terminals recover their function.7
Anecdotally, and in one publication,8 it appears that reconstituted toxin that has been allowed to sit unused for weeks may have the same initial effect, but a possibly decreased duration of action.9
Indications
The FDA cosmetic approval for Botox is only for glabellar rhytids in patients under 65 years of age, but I have used it in my practice for patients in their eighties and I have injected every muscle in the face.
Complications from aesthetic surgical procedures
Many complications from aesthetic surgical procedures can be effectively treated with Botox.
Preoperative History and Considerations
Functional anatomy
A classic paper that deals with functional anatomy is Rubin’s description of the different smile patterns from 1974.12 Although all individuals have the same mimetic muscles, their smile patterns are very different depending on which muscles dominate within the group. Even within a single muscle, different portions of that muscle can dominate and severely alter animation. The key is to analyze each patient’s face and discern which portions of which muscles dominate facial activity and cause wrinkles or unaesthetic shaping of the face.
Glabella
Operative Approach
The glabella was the first area to be treated cosmetically with Botox.6 Surgical debulking of the glabellar musculature is an established practice and chemodenervation of these muscles has much the same effect.