Chronic migraine: current concepts and ongoing treatments.

Migraine is an episodic painful disorder occasionally developing into a chronic form. Such disorder represents one of the most common neurological diseases in clinical practice. Chronicization is often accompanied by the appearance of acute drugs overuse. Chronic migraine (CM) constitutes migraine's natural evolution in its chronic form and involves headache frequency of 15 days/month, with features similar to those of migraine attacks. Medication Overuse Headache (MOH) has been defined as a headache present on > or = 15 days/month, with regular overuse for > 3 months of one or more drugs used for acute and/or symptomatic headache management. Subtypes of MOH attributed to different medications were delineated. Misuse of ergots, triptans, opioids or combination analgesics on > or = 10 days/month was required to make the diagnosis of MOH, while > or = 15 days/month were needed for simple analgesic-overuse headache. CM's low prevalence produces an extremely high disability grade. Therefore, special attention should be paid to both control and reduction of risk factors which might favour the migraine chronicization process and/or the outbreak of MOH. In MOH sufferers, the only treatment of choice is represented by drug withdrawal. Successful detoxification is necessary to ensure improvement in the headache status when treating patients who overuse acute medications. Different procedures have been suggested for withdrawal namely at home, at the hospital, with or without the use of steroids, with re-prophylaxis performed immediately or at the end of the washout period. At the moment we have not a total agreement whether prophylactic treatment should be started before, during, or after discontinuation of the overuse drug. Both drugs have been approved for CM treatment in view of their well-defined resistance to previous prophylaxis drugs. Recently, the PREEMPT clinical program has confirmed onabotulinumtoxinA as an effective, safe, and well-tolerated prophylactic treatment for adults with CM.