Seventeen percent of women and 6% of men in the United States have migraines.
16 Current prophylactic antivasospastic therapy with beta-blockers and symptomatic therapy with selective serotonin receptor agonists (eg, sumatriptan succinate, zolmitriptan, naratriptan hydrochloride) have shown limited benefit.
16 In a double-blind study by Silberstein and Lipton,
17 123 patients with two to eight moderate to severe migraines per month received BTX-A injections of 25 U or 75 U into the glabellar, frontalis, and temporalis muscles. Results showed that 25 U—but not 75 U—of BTX-A was superior to the control treatment (saline) in reducing the frequency and severity of migraines, the need for migraine medications, and associated vomiting (
Table). In a double-blind study by Brin et al,
18 53 patients with two to six migraines per month received BTX-A injections into the frontal and temporal musculature (
Table). The results of this study
18 showed that BTX-A was superior to placebo in reducing migraine severity at 12 weeks postinjection. The effect of BTX lasts much longer (3 months) than traditional treatments, is generally well tolerated, and has fewer systemic adverse effects.
The origin of migraine cephalgia remains unknown, but it has been hypothesized that vascular, neuronal, and musculoskeletal components exist. The injection of BTX-A acts on the myofascial component by inhibiting contraction of the respective cranial muscles, but it also acts on the vascular component by inhibiting the release of ACh. Thus, the parasympathetic vasodilatory response is inhibited. It is also possible that BTX-A blocks neurotransmitters other than ACh that are involved in the cascade of events leading to a migraine.
19 Vasoactive intestinal peptide and vasoconstrictor neuropeptide Y have been found with ACh in parasympathetic nerves originating in internal carotid ganglia innervating cerebral arteries.
20 Another mechanism by which BTX-A may relieve migraines is in its action on pericranial muscle spasms that pull on the skull bones and their respective sutures, causing a change in intracranial pressure and pressure on the cerebral vasculature.