Myasthenia Gravis and Botulinum Toxin: Contraindication

Botulinum toxin is one of the most frequent procedures in facial harmonization, and that creates a trap: familiarity makes the medical history seem like a detail. In some conditions, it is the opposite. Myasthenia gravis is the classic example of a disease in which the toxin's mechanism and the disease's mechanism meet at the same point, the neuromuscular junction.

This text is a review focused on safety. It does not replace the package insert of the product you use or the assessment of the physician following the patient. The final decision belongs to the licensed professional, following the rules of their professional board. For the context of neuromuscular diseases in general, see neuromuscular diseases and toxin.

What is myasthenia gravis?

Myasthenia gravis is an autoimmune disease in which antibodies attack receptors at the neuromuscular junction, the point of communication between nerve and muscle. The result is muscle weakness that worsens with effort and improves with rest, fluctuating in intensity through the day.

The most commonly recognized manifestations are:

• drooping eyelid (ptosis) and double vision (diplopia);
• weakness in chewing, swallowing and speaking;
• weakness of the facial muscles;
• weakness of the limbs and, in crises, respiratory compromise.

Many patients have the condition controlled with medical follow-up, but the disease can have periods of worsening. There are also ocular forms, restricted to the eyes. The patient does not always connect the disease with "aesthetics" and may not mention the diagnosis if no one asks.

Why is the toxin a problem in this context?

Botulinum toxin acts by preventing the release of acetylcholine at the neuromuscular junction, through cleavage of proteins such as SNAP-25. As a result, the target muscle temporarily loses strength. That is exactly the desired effect in dynamic wrinkles.

In myasthenia, the neuromuscular junction already has fewer functional receptors. Adding a pharmacological blockade can:

1. Worsen weakness in the treated muscle, more than expected.
2. Worsen weakness in distant muscles, through spread or a systemic effect, phenomena described with toxin in other indications. See toxin spread.
3. Precipitate bulbar symptoms, such as difficulty swallowing and speaking.
4. In severe cases, affect breathing.

Because the toxin's effect lasts months, the problem does not resolve in hours. That is why prevention is the central approach. For an overview of complications, see complications with botulinum toxin.

What do the package inserts say?

Package inserts for botulinum toxin registered in Brazil usually list neuromuscular junction diseases, such as myasthenia gravis and Eaton-Lambert syndrome, among the contraindications or major precautions. The wording varies between products, and it is your obligation to read the insert of the product you use, rather than relying on memory or third-party summaries.

For reading product documents, see how to read an injectable's instructions for use. And remember: using outside what the insert directs is off-label use, with greater responsibility and specific consent.

How do you identify the risk at the consultation?

The medical history is the only barrier between the patient and the event. It must be systematic, and not depend on the patient remembering.

1. Ask directly about neurological and neuromuscular diagnoses, including myasthenia gravis, myasthenic syndrome, amyotrophic lateral sclerosis and others.
2. Ask about symptoms: drooping eyelid, double vision, weakness that worsens through the day, difficulty chewing, swallowing or speaking.
3. Review medications, including pyridostigmine, immunosuppressants and antibiotics. See aminoglycosides and botulinum toxin.
4. Watch for signs: drooping eyelid, nasal speech, fatigue while speaking.
5. Record the answer in the patient record, even when negative.

The full script is in medical history in facial harmonization. In cases of suspicion without a diagnosis, do not inject and advise the patient to seek medical assessment.

What should you do if the patient has the diagnosis?

The prudent approach is not to inject without a specialist assessment. Two routes are possible:

• Do not perform the procedure and offer alternatives that do not involve the neuromuscular junction, as far as makes sense for the concern. See the overview of options in botulinum toxin: fundamentals.
• Request an assessment by the treating physician, who may advise against it or, in selected cases, discuss risk and benefit. If, after the conversation, the physician and the professional decide to proceed, the decision, the informed consent and the justification must be documented.

On either route, document. The patient needs to understand the reason, without embarrassment.

What if something happens after the injection?

If a patient with an unknown condition shows significant weakness, drooping eyelid, or difficulty swallowing, speaking or breathing after the toxin, it is an emergency: call the emergency service and report the recent toxin injection. Follow the office's emergency protocol (see emergency kit for the facial harmonization office). Report the event according to the rules (see adverse event reporting (NOTIVISA)).

Does Harmy have a role here?

Harmy does not do clinical screening and does not replace the medical history. It simulates volume in marked areas and does not assess health. For toxin, the only connections are with the Glabella and the Chin: the app lets you mark the point and simulate a symbolic unit, which does not represent a clinical dose.

For the general flow, see how to use Harmy.

Review quiz

Myasthenia gravis and botulinum toxin belong to the category of risk that is resolved entirely through prevention. Asking, documenting, reading the package insert and, when in doubt, not injecting costs little. Not asking can cost an emergency.