Medication overuse headache is the most common form of secondary chronic daily headache seen in headache practice, 8–10 and probably accounts for about half of cases of chronic daily headache. 11–13
Different terminology confuses the issue
Many terms have been used to describe medication overuse headache in the past, such as analgesic-rebound headache (or just rebound headache), transformed migraine with medication overuse, and even chronic migraine. The lack of uniformity in terminology makes for confusion in the literature and difficulty in communicating with patients and colleagues. Some authors mean medication overuse headache when they say chronic daily headache.
Complicating this diagnostic confusion is a debate as to whether chronic daily headache in general should be treated as a primary or secondary headache disorder. Some European headache specialists insist on a strict division between primary and secondary daily headaches, and medication overuse headache is one of the latter. Many American specialists believe that chronic daily headache is a collective description or phenotype rather than a diagnostic category, and that it is usually associated with and exacerbated by medication overuse. 14,15 The International Classification of Headache Disorders uses the term “chronic migraine” for primary daily headache, and “medication overuse headache” for secondary daily headache or rebound.
Many American specialists approach the disorder clinically, treating chronic daily headache in the same way regardless of whether there is medication overuse. They cite randomized controlled trials of topiramate (Topamax) and onabotulinum toxin type A (Botox) that reported comparable benefit with these medications in patients with chronic daily headache with or without medication overuse. 16–18
MORE IS LESS: THE PARADOX OF TREATING ACUTE HEADACHE
The clinical paradox and dilemma of treating acute episodic migraine is that more is less: the more days of acute treatment, the less well the migraines are controlled. And thus, the patient is likely to veer out of control. 3
The compassion that motivates us to prescribe medications for acute episodic migraine must be tempered by the realization that too much of a good thing will result in its malignant transformation to medication overuse headache. Once this develops, preventive and migrainespecific acute medications are less effective, and patients need far more complex interventions.
Complicating the dilemma, acute migraine-specific medications such as triptans and dihydroergotamine (Migranal) work better when taken early in migraine attacks, before central sensitization and allodynia develop with attendant photophonophobia and sensitivity to other stimuli. On the other hand, overuse will lead to medication overuse headache.
The symptoms of medication overuse headache vary in frequency, severity, location, quality, and associated features, both among patients and in the same patient. This is because the disease itself varies and also because of differences in the type and frequency of medication intake. Still, some features help to define this problem, and failing to recognize them may account for a widely held clinical feeling that these patients are “difficult.”
History of episodic migraine. Generally, medication overuse headache does not occur in nonmigraineurs.
Headache on most days of the month. Whenever a migraineur starts having headaches on more days than not, the diagnosis of medication overuse should be considered.