Chronic migraine represents the majority (40–60 %) of the clinical forms of headache observable in a third-level headache center. The prevalence of chronic migraine in the global population is approximately 2 %. Persons suffering from chronic migraine represent a subpopulation of patients with a high risk of disability profile, a high psychiatric comorbidity, and detrimental economic impact.

The recent headache classification from the International Headache Society (2013) defines chronic migraine as a form of migraine present in patients with a previous clinical history of migraine for more than 15 days per month. The clinical criteria for such disease are: at least 8 days per month with migraine characteristics, either registering the presence of aura or not, for at least 3 months.

The chronic migraine patient shows a widely variable developmental pattern from the episodic to the chronic form, with the alternation of phases of rapid increase in crisis frequency and stabilization, almost always leading to chronicity in a “Rossini Crescendo.”

Emergency MRI is recommended only in cases of severe, rapid, and pharmacologically noncontrollable development of the pain, described as the worst pain ever suffered (known as “thunderclap headache”), associated with positivity at the neurological examination, and cognitive or neuro-ophthalmologic alterations. It is then possible to evaluate whether the exacerbation phase hides other life-threatening abnormalities in the craniocephalic area, such as subarachnoid hemorrhage, fissuring or breaking of a brain aneurysm, cerebral venous thrombosis, cervicocephalic arterial dissection, cerebral vasoconstriction syndrome, spontaneous intracranial hypotension, or other craniocephalic abnormalities. In patients with chronic migraine complicated by medication overuse, one should look for an underlying cause only in the case of true red flags, not in the more frequent cases of refractoriness to the usual acute-treatment drugs: access to the ED must be explained in detail and not be pushed by an unmotivated fear. It must be borne in mind that in Europe 2 % of the admissions to the ED are classified as headache, the majority of which are chronic migraines, but all of these patients, for evident medicolegal reasons, undergo brain CT scans.

On the other hand, there are many forms of chronic migraine that can be positively treated with the botulinum toxin therapeutic technique which, if applied early, offers the opportunity of de-chronicization from chronic migraine complicated by medication overuse. The treatment scheme has been coded by two large randomized controlled trials (PREEMPT1, PREEMPT2), and is based on quarterly sessions of infiltrations with OnabotulinumtoxinA, following a standardized injective paradigm based on the application of 155 U of OnabotulinumtoxinA in 31 sites, following the Fixed Doses Fixed Sites (FDFS) procedure. An additional 40 U can be injected unilaterally or bilaterally in three specific areas (neck/head) according to the Follow The Pain (FTP) procedure.

In the recent International Classification of Headache Disorders 3 beta (ICHD-3β), chronic migraine has been inserted in the main body of primary headaches and rightly, therefore, is part of the classification system. The secondariness of medication overuse or addiction to analgesics in this chronic migraine category has not yet been cleared, even though we now have therapeutic means aimed to treat these two strongly overlapping clinical situations. In any event, clinicians today have a well-defined diagnostic and therapeutic pattern for chronic migraine that can be of great help to both the headache expert and the family physician (see Sect. 5.4).

Early treatment of chronic migraine is preferred. Forms of chronic migraine that are treated too late develop, over the years, into multiple episodes of MOH despite the rehabilitation procedures of withdrawal from drug abuse, which offer a good platform for the beginning of OnabotulinumtoxinA therapy but at long-term follow-up inexorably develop into refractory chronic migraine; at this point a further mini-invasive treatment is requested, such as occipital or spinal neurostimulation.

The patient was admitted to the outpatient section of our Regional Referral Headache Center via the preferential online request made through the ED physician. The diagnosis of chronic migraine was readily reached based on the 2013 ICHD-3β criteria. This classification states that chronic migraine (ICHD-3 code 1.3) can be defined as a headache, both migraine and/or tension-type like, appearing for a 3-month period for more days than not on a monthly basis. Diagnosis must follow the criteria of migraine without aura (ICHD-3 code 1.1) or with aura (ICHD-3 code 1.2). During this 3-month observational period the number of migraine days must be more than 8 per month and the use of triptans or ergot derivatives, with derived benefit, must be deduced from the headache diary.