Botulinum toxin exerts its effect by cleaving key proteins required for nerve activation. First, the toxin binds specifically to nerves which use the neurotransmitter acetylcholine. Once bound to the nerve terminal, the neuron takes up the toxin into a vesicle. As the vesicle moves farther into the cell, it acidifies, activating a portion of the toxin which triggers it to push across the vesicle membrane and into the cell cytoplasm. Once inside the cytoplasm, the toxin cleaves SNARE proteins preventing the cell from releasing vesicles of neurotransmitter. This stops nerve signaling, leading to paralysis.
García Leiva specified that this treatment "is not a first-choice treatment for migraine sufferers, but it can only be applied in patients with chronic migraine who have tried several treatments with poor results, and who show peripheral sensitization of muscles. Recently, the Foods and Drugs Administration (USA) has approved botulinum toxin as a therapeutical drug for the treatment of chronic migraine.
"Neurotoxins and facial fillers are my most popular injectable treatments," notes Zeichner. "Neurotoxins like Botox and Dysport relax muscles under the skin that can lead to folding and lines, specifically frown lines between the eyebrows. Facial fillers are my favorite cosmetic procedure in the office—there's really an art to it. I exclusively use hyaluronic acid fillers because they are safe and long-lasting."
It is not known whether BOTOX® is safe or effective to treat increased stiffness in upper limb muscles other than those in the elbow, wrist, fingers, and thumb, or in lower limb muscles other than those in the ankle and toes. BOTOX® has not been shown to help people perform task-specific functions with upper limbs or increase movement in joints that are permanently fixed in position by stiff muscles. BOTOX® is not meant to replace existing physical therapy or other rehabilitation that may have been prescribed.