- The International Headache Society criteria provide a useful standardized way to diagnose migraine clinically.
- Neuroimaging is not necessary for patients who clearly meet clinical criteria for migraine and whose neurologic examination results are normal.
- Over-the-counter drugs (including aspirin, ibuprofen, and the combination of aspirin, acetaminophen, and caffeine) work well and are first-line treatments for mild migraine.
- Migraine-specific medications (including intranasal dihydroergotamine [DHE] and the triptans) are recommended for more severe migraine; little evidence exists to suggest one drug over another.
- Prophylaxis is recommended if patients find the severity or frequency of headaches bothersome enough to warrant preventive measures; amitriptyline, divalproex sodium, and propranolol are effective prophylaxes.
Migraine is a common and disabling condition. Among adults in the United States, approximately 18% of women and 6% of men report symptoms consistent with migraine1; less than half have been diagnosed by a physician or received prescription treatment from a physician.2 Migraine accounts for more than 2.8 million visits per year to US physicians and is the reason for encounter in about 1 visit per week to the typical family physician.3 Migraine is estimated to cost US employers more than $13 billion each year; direct medical costs exceed $1 billion annually.4
The exact pathophysiology of migraine is unknown. The prevailing theory is that a trigger (such as fatigue, stress, or certain foods) sets off a wave of brief neuronal activation, followed by a more sustained neuronal inhibition known as cortical spreading depression (CSD). At some point the trigeminovascular system is activated (possibly by CSD), releasing vasoactive neuropeptides that cause a painful inflammatory response in the meninges. Stimulation of presynaptic serotonin receptors inhibits release of the inflammatory neuropeptides; this is one possible explanation for the effectiveness of the triptans.5
Migraine is a syndrome diagnosed by a certain combination of signs and symptoms. The International Headache Society (IHS) diagnostic criteria (Table 1) are widely accepted as the reference standard for the diagnosis of migraine, as well as that of other types of headache.6 Although they were originally intended to assist in the standardization of research subjects, the criteria for the most common headache disorders can be adapted for diagnosis in the clinical setting. Migraine diagnosis is based almost entirely on the history; the main role of the physical examination is to screen for life-threatening conditions, such as intracranial hemorrhage or tumors.
In some patients, migraine is difficult to distinguish from other primary or secondary headaches, especially tension-type headache. A recent meta-analysis demonstrated that the features most helpful to rule in migraine (compared with tension-type headache) are nausea (positive likelihood ratio [LR+] = 19.2), photophobia (LR+ = 5.8), and phonophobia (LR+ = 5.2). Table 2 provides additional information regarding these and other significant findings, including the post-test probabilities of migraine given the reported prevalence among adult men and women in the United States. The likelihood ratios are probably somewhat inflated, since many of these symptoms are also part of the criteria for the reference standard (“incorporation bias”). The IHS criteria for migraine without aura require nausea or the combination of photophobia and phonophobia to make the diagnosis; it is therefore not surprising that these findings would be the most specific.
While the presence of any single feature may not be sufficient to clinch the diagnosis, sequentially combining the post-test probabilities can prove useful in cases that are not straightforward. For example, a woman with a family history of migraine who complains of a unilateral headache accompanied by photophobia but no nausea has an approximately 80% post-test probability of migraine. This conclusion assumes statistical independence of these symptoms and thus may overestimate the probability somewhat.8
Migraine has no specific diagnostic findings on computed tomography (CT) or magnetic resonance imaging (MRI). The best evidence addressing the use of neuroimaging studies in migraine, as well as most other diagnostic and management issues, comes from the United States Headache Consortium (USHC), a panel of experts from several specialty societies and professional organizations, including the American Academy of Family Physicians. In April 2000, the USHC issued diagnosis and treatment guidelines based on rigorous evidence-based reviews of the medical literature.9 A USHC meta-analysis showed that the prevalence of significant abnormalities on head CT or MRI for migraine patients with a normal neurologic examination ranged from 0% to 3.1% with an overall prevalence of 0.18% (1 in 555).10 Therefore, the USHC does not recommend neuroimaging for patients with a normal neurologic examination who meet the IHS diagnostic criteria for migraine (level of evidence [LOE]: B, using the Centre for Evidence-Based Medicine classification scheme). Neuroimaging should be considered for patients for whom a diagnosis is less clear cut (LOE: C).