The popularity of Botox for cosmetic facial uses is that it does something that not even surgery can do…stop unwanted expressions. Its downside is that its results are not permanent. Most patients would wish that its effects were either more long-lasting or were permanent.
One question that some patients ask about the long-term use of Botox is whether it becomes more effective or, conversely, does one become resistant to its effects.In the very long-term (10 plus years of regular use), no one really knows for sure as so few patients have been treated for that long. It is tempting to think that regular use of Botox injection over many years results in muscle atrophy and either an increased response to injections or the need for less treatments or lower doses over time.
New research might give some insight into whether such effects from Botox may actually happen. A study shows injections turn muscle to fat. The findings were part of a new study by researchers at the Faculty of Kinesiology at the University of Calgary.
The study found that animals injected with botulinum type A neurotoxin complex experienced muscle weakness in muscles throughout the body, even though they were far removed from the injection site. The study also found that repeated injections induced muscle atrophy in the limb that was not injected with the toxin.The study used dosages that approximated therapeutic doses used to treat conditions like cerebral palsy where muscle contraction can’t be controlled resulting in spasticity. This study shows, for the first time, that over time botulinum toxin type A use also results in muscle weakness and atrophy in noninjected muscles far removed from the injection site.
Previous research has also shown that botulinum toxin A easily crosses the muscle membrane barrier, resulting in muscles weakness in the surrounding (noninjected) muscles as well. We call this diffusion or zone of spreading. (it can account for the potential problem of eyelid ptosis or droopiness that may potentially occur with cosmetic injections between the eyebrows)
What do these study results have to do with cosmetic facial injections with Botox? These were limb injections in animals and relate to what happens to limbs that were not injected. Perhaps nothing as the type of muscle and the doses used were in excess of what is injected into much smaller muscles of facial expression. But it may also suggest that long-term Botox use in any muscle may eventually weaken it through ‘disuse atrophy’. We know that easily happens in extremity muscles but does it or will it happen in the muscles of facial expression? Many patients hope so…the next decade of Botox use will undoubtably answer that questions.
Dr. Barry Eppley
Indianapolis, Indiana