If you’ve ever broken a bone that required a cast, you’re likely familiar with the concept of atrophy—the wasting and weakness that can befall a muscle that’s completely immobilized for a period of time. The effects are usually temporary, with muscles gradually rebounding once you start using them again.
Lately, the notion of muscle atrophy—as a side effect of Botox injections—has been swirling around TikTok and Instagram. And like most fear-mongering messages, the posts are stirring confusion and concern. “I’m seeing a lot of misinformation about this on social media, often fueled by individuals who have no medical or scientific background but whose reach can be broad,” says Dr. Sarmela Sunder, a board-certified facial plastic surgeon in Beverly Hills, California. The term atrophy is often misused online and applied to any sort of oddity that occurs when an inappropriate dose of toxin is used or an unintended muscle is hit. As a result, some providers have had an influx of Botox-wary patients asking about atrophy this past year.
In Greenwood Village, Colorado, board-certified dermatologist Dr. Joel L. Cohen, an expert in managing injectable complications, hasn’t yet seen the social media buzz influence his patients directly, but he assures us that significant or lasting atrophy from neuromodulators is a “nonissue.” These drugs work “very precisely and very locally where they’re injected, to block the ability for a nerve to cause a muscle to contract—and the effect is, importantly, temporary,” he says. By sedating select muscles for a few months at a time, toxins stop the overlying skin from creasing and folding, thereby “delaying the imprinting of lines and the prominence or degree of those lines,” he adds. “But the muscle is still there,” Dr. Cohen stresses. “It’s not attenuating to a point where it’s going away.” Much like if you were to suddenly stop doing curls; your biceps may shrink, but they’d still exist and function and possess the capacity to bulk back up.
The truth about Botox and muscle atrophy
Notice, however, that we haven’t flat out refuted rumors of Botox-induced atrophy. And that’s because there’s actually “a partial truth” at play here, says Dr. Sunder. “We are intentionally creating a form of subtle atrophy with toxin injections,” she explains. “We’re hoping that muscle contractility becomes weaker, thereby leading to fewer dynamic lines.”
While the idea of muscle atrophy may seem scary and, as Dr. Cohen points out, tends to connote some type of dysfunction—stroke survivors come to mind—atrophy, in the context of botulinum toxins, suggests something a bit different. Here, “atrophy just means that the muscle fibers get smaller,” says Dr. Jennifer L. MacGregor, a board-certified dermatologist in New York City. “When the face muscles are strong and bunched up, we actually want to ‘atrophy’ them a little, to smooth them out. As the muscles relax and get smaller, they get smoother and the [overlying] wrinkles soften.” She compares the effect of two or three sequential treatments to putting targeted muscles on bed rest for about a year. “The cosmetic effect is fewer lines and a smoother texture,” she says.
Over time, Botoxed muscles tend to get conditioned to being in this zen state, so unfurling them in the future requires smaller and/or less frequent doses of neuromodulator. Essentially, Dr. MacGregor explains, “the muscles learn to rest and don’t bunch up as much when they start working again.” All of this hinges on proper injection technique, of course—strategically atrophying groups of muscles in a synchronized way to undetectable effect.
Why doctors say atrophy fears are “overblown”
To recap, minor muscle atrophy is an expected consequence of neuromodulators. “When muscles aren’t exercising, they get smaller,” reiterates Dr. MacGregor. But in most scenarios, this change is fairly invisible—and, as previously noted, reversible. When you stop getting shots, “the muscles eventually get reinnervated by tiny new nerve branches and work again,” she adds. “They just aren’t quite as strong at first, because they have been resting.”
Botox-related muscle atrophy becomes worrisome only “when large doses are used in areas like the upper face at frequent intervals, for repeated and extended periods of time,” says Dr. Sunder, since this can lead to unwanted volume loss. “Sometimes when you look at older women who’ve been getting toxin for 30 years, their foreheads look thin because there’s not as much padding there—the muscle is thinner than it was before.”
We generally desire fullness in the forehead, a youthful curve, and some mobility—which is why modern injectors tend to undertreat the area with toxin, using only a fraction of the on-label dose, to stave off furrows while preserving expression. Dr. Cohen, who was an investigator for the 2017 U.S. Food and Drug Administration (FDA) study of Botox for forehead lines, explains that in the trial, researchers used 20 units across the forehead in all subjects, in order to predictably achieve the specific degree of improvement mandated by the FDA. In practice, however, “20 units is not something we typically use in the forehead,” Dr. Cohen says, “because it would knock out enough muscle to make the area look heavy and not necessarily feel right to some people, who rely on their forehead to lift up their eyebrows”—a tendency many develop with age when the skin of the upper eyelids gets lax and heavy, he adds.
Recognizing that manufacturer-prescribed doses aren’t always practical for real-world patients, “most ethical, thoughtful, and conscientious providers are not performing high-dose treatments in very frequent settings anymore,” Dr. Sunder says. “This was more common 10 or 20 years ago, but I don’t find it to be standard practice anymore—which is the reason I think [muscle atrophy] is being overblown to an extent.”
Dr. Amelia K. Hausauer, a board-certified dermatologist in Campbell, California, agrees that “with most facial indications [for Botox], like the glabella and crow’s feet, we don’t see a whole lot of atrophy in patients using FDA-approved doses or lower.” She also notes that there’s not much in the scientific literature on long-term muscle atrophy in humans related to neuromodulators, save for a handful of case reports describing small, reversible divots in muscles treated regularly with significant quantities of toxin, mainly for the relief of migraines.
On the flipside, in the medical literature, there’s an abundance of data supporting the safe treatment of conditions like cervical dystonia—a spasticity disorder of the neck—using roughly 200 units of Botox, Dr. Cohen tells us. And in these cases, “there are no ill effects from high-dose, repeat injections over many, many years,” he says. So it seems even generous, serial doses don’t guarantee obvious muscle atrophy—not in large muscles, anyway.
When visible muscle atrophy is the goal
Interestingly, medical uses for Botox have inspired popular cosmetic tweaks, which actually harness the drug’s power to downsize and sculpt select muscles. “In some cases, such as with the masseter muscles [at the corner of the jaw], the trapezius [back of the neck and shoulders], and gastrocnemius [calves], we are intentionally hoping for greater levels of atrophy to shrink the sheer bulk of the muscle [in order] to create more attractive silhouettes,” says Dr. Sunder.
Doctors have been injecting the powerful masseters since the 1990s, to help ease pain associated with chronic teeth clenching and grinding. Those hard-to-break habits overwork our chewing muscles, boosting their mass and giving the lower face a wide, square look. By injecting the masseters with neuromodulator—currently an off-label treatment—you control the muscle-bloating behaviors and give the jawline a more tapered appearance. “We’re treating more of the superior aspect of the muscle—not the whole muscle—to make it less thick, but you’re still able to bite and chew,” Dr. Cohen notes.
Since the masseter is brawny, doctors need to use at least 24 units of Botox per side—“that’s the minimum dose for good efficacy,” says Dr. Hausauer. “I typically start there and gradually increase as needed so I don’t overfatigue the muscle.” At that dose, most patients start to see a change within six to eight weeks. Ultrasound studies have shown a 30% reduction in masseter size at three months after a single injection, with the muscle returning to about half its original size by 12 months post-shot.
Likewise, controlled muscle atrophy is the objective when doctors slim outsize calves or hefty traps with neuromodulators. Dr. Hausauer makes the point that they’re generally not injecting into the same exact areas every time they treat these muscles, which affords individual muscle fibers time to rehab and “gives more of a homogenous softening” of the muscles, she says, lessening the chance of creating isolated sunken spots.
The bottom line on Botox and muscle atrophy
Some degree of muscle atrophy is inevitable with neuromodulator injections—it is, in fact, the goal of treatment, says Dr. MacGregor. But unless you’re actively trying to deflate oversize muscles with larger-than-average doses of toxin or you’ve been freezing your face for years on end and continuously flooding receptors with botulinum, then muscle atrophy should be fairly negligible. And again, once you cold-turkey the toxin, “those muscle fibers, as they get used more and more, will strengthen and return,” says Dr. Hausauer—though, she adds, for some patients, it can take a year or more to get back to baseline or thereabouts.
By using neuromodulators prudently, you can avoid unintentional volume loss, our experts agree. “There has to be a thoughtful way of injecting a patient,” says Dr. Sunder. It helps, of course, if you find a physician you trust and stick with them “rather than bouncing between providers several times a year,” she notes.
Beyond monitoring the frequency of your treatments and the number of units injected here and there, your injector should be reevaluating at each visit, to see how your muscles are changing due to the effects of neuromodulators and aging. This is true whether you’re targeting the muscles responsible for wrinkles or those that you’re hoping to visibly diminish, like the masseters, says Dr. MacGregor. Remember, as those muscles weaken, they usually demand less toxin—and if the dose isn’t adjusted accordingly, the excess could cause problems.
Ultimately, says Dr. Hausauer, choosing an injector who “pays attention to individual faces and how they’re moving differently over time is the best way to minimize unwanted atrophy.”
