Long-term effects of botulinum toxin type A (Botox) on facial lines: a comparison in identical twins.

Objective: To evaluate the presence of imprinted facial lines in identical twin sisters, one of whom had received botulinum toxin type A (Botox) treatment in the forehead and glabellar region regularly for 13 years and one of whom had not. Crow's feet were also compared.

Methods: One twin received Botox in the forehead and glabellar region (approximately 2 to 3 times each year over the past 13 years) and in the crow's feet (twice in past 2 years). Her twin received Botox only twice (in the forehead and glabellar region, 3 and 7 years ago).

Results: Imprinted forehead and glabellar lines were not evident in the regularly treated twin but were evident in the minimally treated twin. Crow's feet were less noticeable when the regularly treated twin smiled (even at 7 months after treatment) than when the minimally treated twin smiled. Untreated facial areas (eg, nasolabial folds) showed comparable aging in both twins. Neither twin experienced adverse effects.

Conclusions: Long-term treatment with Botox can prevent the development of imprinted facial lines that are visible at rest. Botox treatment can also reduce crow's feet. Treatment is well tolerated, with no adverse events reported during 13 years of regular treatment in this study.