Federal health authorities on Friday approved Botox injections for the prevention of chronic migraines in adults, an advance experts described as "modest." In a statement, the Food and Drug Administration recommended Botox be injected approximately every three months around the head and neck to dull future headache symptoms. The drug -- whose generic name is onabotulinumtoxinA -- has not been shown to work against migraines that occur 14 days or fewer per month.