Abstract
Introduction The primary action of botulinum toxin type A (BoNT-A) is to inhibit acetylcholine release from the presynaptic terminal, resulting in reversible chemical muscle paralysis. It is a widely accepted treatment for improving the appearance of glabellar expression lines resulting from muscle contraction.
Materials and Methods We evaluated the glabellar force patterns, facial wrinkle classification, and the number of BoNT-A units used in the corrugator and procerus muscles.
Results The mean total BoNT-A units used were 7.2 IU in the corrugator muscle (7.1 IU in women and 7.4 IU in men) and 3.9 IU in the procerus muscle (3.9 IU in women and 4.1 IU in men), with a positive correlation between the number of units and the age of the 58 participants. Regarding muscle strength pattern, more units were needed in the corrugator muscle with a strong or moderate pattern and facial wrinkle classification ranging from 3 to 4 (8 IU and 8.5 IU, respectively). The procerus muscle required more units in subjects with strong force patterns and wrinkles classified as 3 to 4 (5 IU). Wrinkles with a 3-to-5 classification required the highest number of BoNT-A units.
Conclusion The number of BoNT-A units used is directly proportional to the strength pattern and classification of facial wrinkles, with more units required for strong force patterns and deep wrinkle classifications.
Keywords botulinum toxins, type A - dermatology - facial muscles - rosacea - skin aging
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