Botox (onabotulinumtoxinA) is a prescription medication produced by Allergan. It is approved by the U.S. Food and Drug Administration (FDA) to treat urinary incontinence, prevent headaches in patients with chronic migraines, and reduce upper limb spasms, among other disorders. Botox also can be used to treat jaw spasms, excessive saliva production, and the inability to swallow, which can cause drooling in patients with spinal muscular atrophy (SMA).
How Botox works
To move a muscle, a nerve signal is sent from the brain via a nerve impulse to the muscle. This signal starts as an electrical signal and is changed into a chemical signal at the point where the nerve cell meets the muscle cell (the so-called neuromuscular junction). One such chemical is called acetylcholine. Once released by the nerve cells, it binds to receptors found on the surface of muscle cells signaling them to contract. An enzyme then degrades acetylcholine, resetting the junction so that it is ready for the next nerve signal.
Botox contains a toxin (onabotulinumtoxinA) isolated from a bacterium, which blocks the transmission of the nerve signal by preventing the release of acetylcholine from the nerve cells. Botox acts locally, wherever it is injected, and prevents muscle contraction.
Botox for SMA
Botox can be used to reduce uncontrollable muscle spasms that SMA patients may experience. It also can be used to reduce nerve signals to the muscles of the jaw and throat that can cause problems with swallowing in people with SMA.
A case study published in the journal Brain & Development described the case of a 21-year old patient with SMA type 2 with difficulty swallowing. A videofluoroscopic swallow study (VFSS) was performed that allowed physicians to visualize the patient’s throat as he swallowed. They were able to determine that spasming of the muscle, which controls the passage of food and fluids to the stomach, was causing his difficulty swallowing. They successfully treated the patient by injecting the muscle in question with Botox, which paralyzed this muscle and prevented further spasms.
A small case study in four patients with SMA type 1 who received Botox injections into their salivary glands to reduce drooling was published in the American Journal of Physical Medicine & Rehabilitation. Patients completed surveys to measure their drooling, which included the number of bib changes and the number of mouth wipes before injection, and then for four to six weeks after injection. All patients showed a significant reduction in their drooling and there were no adverse side effects.
Botox can cause minor side effects, including dry mouth, pain or irritation at the injection site, tiredness, and headache. Botox also can cause severe allergic reactions, including rash, welts, and breathing problems.
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