Chronic Migraine With Apparent Loss of Response to Onabotulinum Toxin Type A Due to Local Nitroglycerin Treatment for an Anal Fissure: A Case Report.

Many patients with chronic migraine are difficult to treat. We present a patient with chronic migraine with good response to onabotulinum toxin type A whose headaches worsened in clear temporal relationship to local treatment with glyceryl trinitrate for an anal fissure. Our case shows that the use, even at distance, of nitric oxide donors can be a precipitating factor for migraineurs and should be always inquired in chronic migraine patients. In addition, the presence of frequent headaches should always be ruled out before prescribing such medications.