Since then, several randomized control trials have shown botulinum toxin type A to improve headache symptoms and quality of life when used prophylactically for patients with chronic migraine[88] who exhibit headache characteristics consistent with: pressure perceived from outside source, shorter total duration of chronic migraines (<30 years), "detoxification" of patients with coexisting chronic daily headache due to medication overuse, and no current history of other preventive headache medications.[89]

A BOTOX “treatment” consists of 31 injections to the head and neck areas, if adherence to the FDA approved protocol is followed. Except for injection into the procerus, which is in the midline, all others are paired sets of injections on the left and right sides. Muscles included are the frontalis and temporalis areas as well as the occipitalis, upper cervical paraspinals, and trapezii. The amount injected at each of the 31 injection sites is small—5 units of BOTOX in a volume of 0.1 mL normal saline or sterile water. A total of 155 units is are typically used.
Side effects from cosmetic use generally result from unintended paralysis of facial muscles. These include partial facial paralysis, muscle weakness, and trouble swallowing. Side effects are not limited to direct paralysis however, and can also include headaches, flu-like symptoms, and allergic reactions.[27] Just as cosmetic treatments only last a number of months, paralysis side-effects can have the same durations.[citation needed] At least in some cases, these effects are reported to dissipate in the weeks after treatment.[citation needed] Bruising at the site of injection is not a side effect of the toxin but rather of the mode of administration, and is reported as preventable if the clinician applies pressure to the injection site; when it occurs, it is reported in specific cases to last 7–11 days.[citation needed] When injecting the masseter muscle of the jaw, loss of muscle function can result in a loss or reduction of power to chew solid foods.[27]

If you undergo Botox treatments for migraines, your doctor will typically administer them once every three months. Depending on your response to Botox, your doctor will recommend a length of time for your treatment plan. Each session will last between 10 and 15 minutes. During the sessions, your doctor will inject multiple doses of the medicine into specific points along the bridge of your nose, your temples, your forehead, the back of your head, your neck, and your upper back.

Even if Botox's mechanism isn't always well understood and some of its off-label uses are still unproven, interest in the drug isn't likely to wane. "Botox is a big cash cow for the physicians' practices," says Ronny Gal, an investment analyst at Sanford C. Bernstein who has watched the drug closely for more than a decade. "When I talk to physicians, they say, 'Botox is not a problem. It works and gives you the result you want.' If it works for depression and atrial fibrillation, it could be massive."
Some doctors and dermatologists recommend lying down and resting after a treatment, but Ravitz says she doesn't think there's any need for downtime unless a patient experiences pain. It can take about two weeks to work, though some patients start to feel relief from chronic migraines sooner than that. Ravitz tells me, "If it’s going to work for a patient, one round of the treatment typically lasts for around three months." Though everybody metabolizes it at a different rate, getting it done every three months or so has been found to be effective.

Spread of toxin effects. The effect of botulinum toxin may affect areas away from the injection site and cause serious symptoms including: loss of strength and all-over muscle weakness, double vision, blurred vision and drooping eyelids, hoarseness or change or loss of voice, trouble saying words clearly, loss of bladder control, trouble breathing, and trouble swallowing.