Unlike other neurological disease, migraine does not worsen over time as a matter of course. Migraine may be stable. It may diminish in frequency or severity. Or migraine can worsen, most often gradually, until the chronic pattern emerges.
Migraine progression to chronic migraine is not the norm. Migraine is more likely to be stable, or to remit (especially over age 50.) Nonetheless, migraine progression is not uncommon. Because it is associated with severe impairment, it deserves special attention.
Risk of migraine transformation
Those at highest risk of migraine transformation include:
- Women, especially Caucasian women.
- Those with at least one episodic migraine per week.
- Those with longer duration of disease – migraine usually began in teens or 20’s – ‘transforms’ in 40’s.
- Those who are overweight – obesity raises the risk of transformation to chronic migraine 5x.
- Those with sleep apnea or who snore.
- Those with a history of head injury.
- Those using acute migraine medications more than 2 days/week.
- Those who are ‘heavy’ users of caffeine.
- Those with major life stress may have a 3x greater risk of migraine transformation.
Character of chronic migraine
The transformation to a chronic pattern usually takes place over years and is characterized by gradual change in the character of headache as well as its frequency. Of interest, the intensity of associated headaches may diminish. Excessive sensitivity to light (photophobia) and sound (phonophobia) are less often associated with headache and may be less severe even when present. The incidence of nausea and vomiting associated with headache may follow the same pattern.
Those with chronic migraine often report a mixture of ‘tension type’ and migraine headache symptoms. For those with near daily headaches, it is likely not every headache satisfies the formal definition of migraine. it seems likely that chronic ‘migraine’ is often the overlay of an increasingly severe migraine pattern on a newly emergent ‘tension type’ headache pattern.
Migraine transformation is frequently, but not always, associated with medication overuse. Not surprisingly, as headache frequency increases, so does the patient’s use of both prescribed and over-the-counter analgesics. Nearly 80% of patients with chronic migraine are reported to overuse medications. As such it has been suggested that excess use of medications, especially over-the-counter medications, might hasten the natural progression of chronic migraine. That seems unlikely, but it is extremely difficult to unravel cause and effect.
By strict classification (as defined by the International Headache Society) medication overuse headache (MOH) represents a separate type of headache altogether (though it can co-exist with migraine.) Technically, in the case of medication overuse, chronic migraine cannot be diagnosed until headache medications have been withdrawn for two months without improvement in headache.
While the prospect of medication withdrawal is not welcome by most with chronic headache, a substantial number of patients do improve after cessation of at least some medications.
It is noteworthy that Americans with migraine spend an estimated $2 billion each year on over-the-counter medications for headache relief, and that while many of these pain relievers have been shown to cause ‘rebound’ headaches leading to medication overuse headaches – none carry warnings to that effect.