Peter Goadsby, MBBS: The classification of migraine that we have from the National Headache Society, the International Classification of Headache Disorders (ICHD-3), is now in its third edition. It dissects out a number of primary headache disorders, [including] migraine without aura and migraine with aura. About 25% of patients have migraine with aura, and these patients have a neurologic disturbance, lasting 5 to 60 minutes, that typically happens before the pain starts, and 90% of it will be visual disturbance—jagged white lines that move across the visual field and grow in size, leaving an area behind, a so-called scotoma.
Now, 75% of patients don’t have that; they have migraine without aura. The migraine with aura patient will typically go on to have the headache phase and the rest of the attack. In migraine without aura, patients will have [a] one-sided headache. It will be throbbing or pounding; it will be moderate or severe. It will be made worse with movement—any of those. Or they’ll have nausea or vomiting, or photophobia and phonophobia—one of those. And it’s taken together, [which] are what you might describe as canonical migraine symptoms that differentiate the two.
Now in ICHD-3—the National Classification of Headache Disorders, the third edition—episodic and chronic migraine are dissected out. In fact, we don’t use the two in episodic migraine. It’s coming [into] the general lexicon, and when I use it, I’m really referring to migraine with or without aura, on less than 15 days a month. That’s the umbrella that you might say would be episodic migraine. Chronic migraine is taken to occur when a patient has at least 15 days of headache in the previous three months, of which half of them should be clearly linked to migraine—either had typical symptoms or had to be treated with an acute migraine treatment.
Now if I was to contrast migraine in the classification system with cluster headache, which falls under the trigeminal autonomic cephalgias (TACs), a cluster headache comes in two forms. When we use episodic and chronic in cluster headache, we’re actually talking about the first bout. In the ICHD, the third edition of the classification, a patient needs a three-month break to have episodic cluster headache, and previously what we’d done [is] we’d only used a month.
So the episodic chronic in cluster headache refers to the breaks; whereas in migraine, episodic and chronic really refer to the number of days per month—the words are the same, but our definitions are very different.
Now a typical patient with cluster headache will have a one-sided headache; it will be very severe, more severe than any other pain that they will describe. And it will occur in bouts—the so-called clusters—that will typically last 8 [or] 10 [or] 12 weeks, maybe once or twice a year, where they’ll have anywhere between an attack every day to 8 attacks a day. The attacks will usually last an hour or two, strictly one-sided, very severe pain, with what are called cranial autonomic symptoms; so eye watering, eye redness, nasal congestion or running, and ear discomfort, eyelid drooping or swelling, flushing, or sweating of the face.
In general terms, the prognosis of migraine is excellent. If you live long enough, migraine almost invariably stops. We know that migraine occurs in about 6% of children, and the ratio of males to females is 1:1. At puberty, the ratio of [females to] males picks up. So, at the peak prevalence [for] migraines—which [for] females in North America [is] about age 41, and there will be 3 females for every male. The one-year prevalence for episodic migraine will be around 30%—about 27%. Now this tails off at menopause, and there’s quite a drop in the female prevalence. With time, the one-year prevalence of migraine drops off. So in general terms, migraine tends to improve with time.