Classification of Migraine
International Headache Society 1988 Diagnostic Criteria
In an attempt to rationalize diverse and sometimes contradictory guidelines, the International Headache Society (IHS) devised consensus classification and diagnostic criteria for headaches in 1988.27,28 The IHS defined migraine as intermittent attacks of headache lasting 4 to 72 hours, accompanied by autonomic symptoms.28 Headache pain must meet at least two of four IHS criteria to be considered migrainous: unilateral, pulsating or throbbing; at least moderately severe; aggravated by activity; and accompanied by autonomic symptoms. The IHS divides headaches into primary (Table 1) 28 and secondary disorders.28 Tension headaches, which are experienced by 70% of people at one time or another, result from muscular tension or stress. Migraine ranks second to tension headaches in prevalence but requires greater utilization of medical resources because of the greater disability it inflicts. Cluster headaches, an uncommon type, are marked by frequent attacks of minor pain in cycles lasting weeks or months followed by lengthy remissions. Etiologies of secondary headaches include vascular disorders, intracranial pathology, sinusitis or other infection, metabolic derangements, or the effects of (or withdrawal from) drugs, toxins, or alcohol.
Migraine should be suspected whenever an individual presents with episodic headaches, particularly disabling ones. In the right circumstances, anyone can have an isolated migraine attack, but migraineurs suffer frequent episodes. Some migraineurs experience tension and/or cluster headaches as well as migraine attacks, a pattern that may confound the diagnosis. Migraine headaches typically start on one side of the head (a signature of vascular headaches) and are accompanied by autonomic symptoms such as nausea, vomiting, diarrhea, photophobia, phonophobia, and osmophobia (intolerance of odors). A recent study in The Netherlands suggests that interictal (between episodes) photophobia is common in migraineurs and is associated with cortical hypersensitivity.29 These data suggest that self-reported photophobic symptoms are reliable guides to headache category and that physicians should inquire about light sensitivity during intervals between attacks.
Preliminary Steps in Diagnosis
The first step in diagnosis should be to ask the patient about the circumstances surrounding his or her headaches. (Sample questions are listed in Table 2.) The interview may provide clues to other conditions (eg, sinusitis, allergy, or depression) that might cause the migraine headache or occur independently, possibly masking the migrainous disorder. Knowing the patient's family history may reveal a genetic predisposition, since 50% to 60% of migraineurs have a parent with migraine. It is also useful to know when patients had their first attacks, since over 90% of migraineurs experience an attack before the age of 40. Initial onset of attacks after the age of 55, especially in association with other changes (malaise, myalgia, and arthralgia) should raise suspicions of organic causes. Underlying pathology may be suspected if pain is bilateral or always occurs on the same side of the head. Frequency and duration of episodes are significant. Migraine attacks last from 4 to 72 hours and do not occur daily, so shorter or more frequent attacks tend to rule out migraine. About 50% to 80% of migraineurs have a prodrome (premonition that an attack will begin in a matter of hours). Prodrome symptoms can be vague and may include hard-to-define symptoms such as yawning, fatigue, food cravings, mood changes, mental vagueness, and fluid retention.28
Migraine without aura and migraine with aura are the two main clinical subtypes. Other subtypes include basilar artery migraine (which occurs mainly in adolescent and young adult women and is influenced by the menstrual cycle), ophthalmoplegic migraine (in which the headache is concentrated around the eye and is associated with vision problems), and status migrainosus (a rare form that can last longer than 72 hours and produce pain so severe that the sufferers are hospitalized).
Migraine Without Aura
Migraine without aura (formerly referred to as "common migraine") accounts for up to 80% of migrainous episodes, while migraine with aura (formerly referred to as classical migraine) occurs in only 15% to 20%.28 The two syndromes are not mutually exclusive, and some patients experience both types during their lifetime.30 Migraine without aura is diagnosed largely based on patient history.
Obligatory criteria include at least five attacks with the following characteristics:
The differential diagnosis must exclude tension headaches and cluster headaches. Tension headaches tend to be bilateral, are associated with mild to moderate pressing pain rather than intense pulsatile pain, are not aggravated by routine physical activity, and may be associated with nausea but seldom with vomiting. A positive family history of migraine and a positive response to pharmacologic therapy with a triptan agent are other clues that discriminate between migraine without aura and tension headaches. Cluster headaches are marked by brief episodes of severe pain that last less than 4 hours, compared with 4 to 72 hours for migraine attacks.28 Moreover, unlike either migraine or tension headaches, cluster headaches are more prevalent in men than in women. The pain of cluster headaches is localized to the orbital or temporal region on one side of the head and is associated with unilateral conjunctival infection, lacrimation, nasal congestion, rhinorrhea, and other symptoms that are atypical of migraine.
Migraine With Aura
The defining characteristics of migraine with aura are the transient neurologic symptoms-predominantly visual-that precede attacks. Aura is accompanied by the typical second-stage symptoms of migraine without aura. The visual disturbances are vivid, consisting of bright flashing lights, scintillating scotoma (a luminous appearance with a zigzag outline that begins in the center of a visual field and radiates outward), and hemianopia (blind spots in half of the visual field in one or both eyes). Nonvisual aura symptoms may include unilateral paresthesia in the form of a tingling sensation in one hand or the perioral region, unilateral weakness, dysphasia (speech difficulty), and confusion. The headache itself is the third stage of the attack. About 80% of migraineurs also experience a fourth stage, or postdrome, in which less intense migraine symptoms persist after the headache phase has passed.28
Given such a symptom set, it should not be difficult to complete the differential diagnosis. Unlike headaches secondary to intracranial pathology, the neurologic symptoms of migraine with aura generally subside within 60 minutes. Post-traumatic headaches such as the postconcussion syndrome may present a diagnostic challenge because they produce symptoms resembling those of migraine or tension headaches. Unlike migraine, however, post-traumatic headaches are often accompanied by vertigo and longer-lasting deficits of memory and concentration.
The IHS criteria for migraine with aura require at least two attacks that meet 1) the criteria for migraine without aura and 2) at least three of the following additional conditions 28:
Role of Neuroimaging in Diagnosis of Migraine
Most patients presenting with headache complaints have tension or migraine headaches rather than headaches secondary to underlying pathology. Therefore, neuroimaging with computed tomography or magnetic resonance imaging, which adds to the cost of medical care and poses the risk of allergic reactions or oversedation, is generally unnecessary.31 However, this might be outweighed by other considerations, such as allaying some patients' deep anxiety.31 Other circumstances that warrant neuroimaging include unexplained abnormalities found on clinical examination, atypical headache features, headaches that do not fit the IHS definition of migraine or other primary headache disorder, additional risk factors for intracranial pathology (eg, existing immune deficiency or neoplasia), and litigation concerns. The US Headache Consortium (USHC), a 14-member multidisciplinary group led by the AAN, has formulated guidelines for the use of diagnostic neuroimaging.31 These guidelines are based on evidence from randomized clinical trials as well as on a consensus of the USHC when data from randomized controlled trials were unavailable. Only six of 28 studies entered into the USHC metaanalysis were prospective, and none of these was blinded. Consensus was reached on three general principles 31:
1. Testing should be avoided if it will not lead to a change in management
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