Can Botox cause the brain to stop using a muscle, resulting in a permanent effect?

There is no known case of Botox or any other neurotoxins such as Xeomin or Dysport having a permanent effect on a brain-to-muscle neuro connections. When it comes to a larger muscle like masseter the idea is that with routine and repetitive injections to achieve some loss of muscle bulk/ weakness from a disuse standpoint or at least keeping the muscle weak while the toxin is active.

The neuromodulators Botox, Dysport, and Xeomin are injected directly into targeted muscles, where they block nerve signals that prompt the muscle to contract. This only affects the receptors in the muscles themselves. None of the neuromodulators get into the bloodstream or affect the brain’s signals. The brain’s signals are still sent; the message is just blocked in the muscle. With time, however, the brain may no longer send the signals, as it has been “taught” that they do not have an effect. That may be why we see effects from continued treatment last longer and longer with repeated treatments over years. Botox’s  (Xeomin, Dysport) effects are not permanent. In the masseter, they stop blocking nerve signals after about 6 months. Over time the treated muscles become a little weaker because they’re not contracting as much. Similarly, if you stop flexing your biceps and training them with weights, they’ll weaken too. A weakened muscle doesn’t do as much damage to the skin, so your Botox may last a little longer. Please consult a board-certified dermatologist who is an expert with Botox, Xeomin, and Dysport to have your masseters treated. 

Disuse atrophy is the reason the muscle has less bulk after being treated with botox.  However after the botox wears off, over time the muscle mass will return.  Sometimes doctors stretch the truth either due to a lack of understanding or the need to embellish the effect of treatment in order to entice you to have treatment.  Botox and its effects are not permanent.

Long term use of botox should cause a weakness in the muscle-similar to 'disuse atrophy'-meaning that the less you use it, the weaker it becomes. Kind of like if you stop going to the gym after a lifetime of working out, your muscles become smaller.Best.

Botox results are not permanent. Botox results resolve in 3-4 months. However, Botox can prevent areas from worsening and in this case, will help the muscle atrophy, appearing smaller. Best, Dr. Emer

Botox can work well to relax muscles that cause wrinkles or relax the masseter muscles, but the effects are not permanent.  Results from Botox can last 3-4 months and in some cases as long as 6 months, but if the treatment is not repeated, the muscle will be able to move as before.  

After using Botox for awhile, the treated muscle eventually weakens. This is partly because the brain does stop sending signals, since the muscle doesn’t act on them anymore. However, once the Botox wears off and the muscle begins to move again, the signals return. This happens no matter which muscle is treated. A board-certified dermatologist will be able to explain the benefits of Botox and give you the best results.

Botox does not have permanent effects on muscles.  It typically wears off in 3-4 months.  For some muscles such as the masseters, the effects can last longer - up to 6 months.  Without repeat treatments, the muscles return to baseline activity.

Botox will not permanently stop muscle movement. Once the botox wears off, the brain will begin to activate the muscle again. Sometimes it may appear that the effects last longer simply because the muscle have become weaker over time from disuse, however the muscle will quickly return to their natural strength and size if you stop using botox. Hope this helps!Johnson C. Lee, MD
Board-Certified Plastic Surgeon
IG: @drjohnsonlee

Thanks for the question. I certainly agree with the other answers that the action of BOTOX is never permanent. Repeated use can cause a disuse atrophy where the muscles shrinks in size but this will only ever be temporary while you continue back-to-back treatments.
Dr Chris Macdonald