The Migraines: Introduction

Jes Olesen

Peter J. Goadsby

Migraine is an important and fascinating disorder. It is important because it is highly prevalent and severely disabling. The total sum of suffering caused by migraine is probably higher than that of any other kind of headache. The fascination stems from its rich and varied symptomatology which, especially in migraine with aura (MA), is a window into certain aspects of the function of the human brain. Furthermore, after many years during which migraine mechanisms seemed elusive, the understanding of this disease is now rapidly increasing, and a coherent model of its mechanisms has been proposed (see Chapter 42). The neurobiological nature of migraine can no longer be doubted.

Migraine was not clearly defined or classified until 1988 (6), and its subforms have only in recent years been studied individually. Most drug trials have examined MA and migraine without aura (MO) together. In contrast, a substantial number of studies on migraine mechanisms and all genetic studies have focused on subtypes of migraine. Although we know more and more about the subtypes, a substantial part of our knowledge still originates from studies in which patients suffering from MO and MA (previously common and classic migraine, respectively) were mixed. Consequently, it is still not possible to cover all aspects of MA and MO separately. Furthermore, many patients have both types and it remains unclear to which extent it is desirable to separate MO and MA. In this book, we generally discuss MO and MA together, but whenever solid knowledge is available they are either discussed separately within the same chapter or, more rarely, in separate chapters. After MO and MA we discuss the rarer and more distinct subforms of migraine separately. The international classification of migraine (7) is given in Table 24-1.

INTERRELATIONSHIPS BETWEEN MIGRAINE WITH AND WITHOUT AURA

To which extent are MA and MO interrelated? The great majority of patients who suffer from MO have never had an attack of MA. On the other hand, among patients who have attacks of MA, it is very common to also have attacks of MO. In population-based studies, the co-occurrence of MA and MO in individual patients was not more frequent than expected than by chance, but in clinic materials it was markedly more frequent (5,13,14). It is a common clinical observation, although never scientifically documented, that MO may change into MA and vice versa. A person may for years suffer exclusively from one form and then later from the other form or from both forms, but it remains uncertain whether this occurrence is greater than by chance. MA and MO both respond to 5-hydroxytryptamine (5-HT₁) receptor agonists (see Chapter 51). It is a generally accepted clinical experience that both forms of migraine also respond to ergot preparations, but this has never been scientifically documented. A methodologically sound and reasonably powerful double-blind trial of metoprolol in the prophylactic treatment of MA showed an effect quite similar to the effect in several trials of MO (9). It thus looks as if the two forms of migraine generally respond to the same treatments. A large number of pathophysiologic studies have shown that dilatation of large intra- and extracranial arteries occurs in both forms of migraine during an attack but that regional cerebral blood flow changes, other than those secondary to pain activation, are present only in MA (see Chapter 37).

Genetic epidemiologic studies and twin studies have shown that MA has a higher familial risk and a higher concordance rate than MO (Chapter 27). Finally, glyceryl trinitrate, which effectively induces attacks without aura in MO sufferers, does not provoke an aura but provokes an attack of MO in patients suffering exclusively from MA (4). The most reasonable interpretation of these interrelationships is that initiating mechanisms are different, although
the painful phase and its associated symptoms are shared by the two forms of migraine (Fig. 24-1).

TABLE 24-1 International Classification of Migraine

1. Migraine
	1.1 Migraine without aura
	1.2 Migraine with aura
		1.2.1 Typical aura with migraine headache
		1.2.2 Typical aura with non-migraine headache
		1.2.3 Typical aura without headache
		1.2.4 Familial hemiplegic migraine
		1.2.5 Sporadic hemiplegic migraine
		1.2.6 Basilar type migraine
	1.3 Childhood periodic syndromes that are commonly precursors of migraine
		1.3.1 Cyclical vomiting
		1.3.2 Abdominal migraine
		1.3.3 Benign paroxysmal vertigo of childhood
	1.4 Retinal migraine
	1.5 Complications of migraine
		1.5.1 Chronic migraine
		1.5.2 Status migrainosus
		1.5.3 Persistent aura without infarction
		1.5.4 Migrainous infarction
		1.5.5 Migraine-triggered seizures
	1.6 Probable migraine
		1.6.1 Probable migraine without aura
		1.6.2 Probable migraine with aura
From Headache Classification Committee of the International Headache Society (7).