Botulinum Toxin Treatment of the Upper Face

Excerpt

Botulinum toxin injection is commonly performed to chemically denervate certain muscles of facial expression for the purposes of facial rejuvenation and anti-aging. Facial rhytids, or "wrinkles," result from repeated contracture of the muscle underlying the facial skin, which over time causes atrophy of the overlying dermis and pleating of the skin. Selective chemodenervation of facial muscles allows for targeted treatment of dynamic rhytids, particularly in the upper face, and also allows for manipulation of eyebrow position and correction of asymmetries. Muscular targets of botulinum toxin in the upper face include the orbicularis oculi, procerus, corrugator supercilii, and frontalis muscles.

Botulinum toxin prevents acetylcholine release at the presynaptic nerve terminal, blocking neurotransmission. Effects usually take up to 2 days to appear, with maximal effect in 1 week to 1 month and last up to 3 to 4 months. Repeated injections of botulinum toxin may cause muscular atrophy in the injected regions, thereby extending the duration of effects. In addition, a retrospective study of 945 patients receiving at least 3 consecutive treatments showed no loss of effect with repeated treatments. After five treatment cycles, patients and providers both rated satisfaction outcomes higher than after the first cycle.

Botulinum toxin is created by fermentation of the bacteria Clostridium botulinum. Botulinum toxin has 7 serotypes from A-G; however, types A and B are practically used for cosmetic applications. Serotype A exists in three formulations to include onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA. Serotype B exists in one formulation, rimabotulinumtoxinB.

RimabotulinumtoxinB is notable for having the most rapid time to onset; however, it also has the greatest area of diffusion and shortest duration of effect. Its acidic pH (5.5-6.5) also increases the discomfort of an injection. Serotype A botulinum toxins, conversely, have a longer onset to action and longer duration of effect. AbobotulinumtoxinA has a greater spread effect than onabotulinumtoxinA and incobotulinumtoxinA, and therefore dose ratios vary. In cosmetic practice, a typical dose ratio is 2.5 to 1 to 1 (abobotulinumtoxinA: onabotulinumtoxinA: incobotulinumtoxinA).