Migraine without aura is the commonest form of migraine (46). It has been suggested (6) that the migraine episode be divided into five distinct phases: (a) premonitory symptoms, (b) aura, (c) headache and associated symptoms, (d) resolution, and (e) recovery (Fig. 43-1). In migraine without aura headache is an essential part of the diagnosis and, although not preceded by any identifiable focal symptoms of neurologic disturbance, as is the case in migraine with aura, it may be preceded by premonitory symptoms, often quite characteristic for the individual and clearly identifiable as the warning symptoms of an impending attack.

The Headache Classification Subcommittee (26) states that premonitory symptoms occur a couple of 2 days to a couple of hours before a migraine attack. They include various combinations of fatigue, difficulty in concentrating, neck stiffness, sensitivity to light or sound, nausea, blurred vision, yawning, and pallor. Premonitory symptoms have been known to precede a migraine attack for centuries (28) and have been classified on clinical grounds as excitatory or inhibitory (5). Excitatory premonitory symptoms include irritability, being “high,” physical
hyperactivity, being obsessional and witty, yawning, excessive sleepiness, increased sensitivity to light and sounds, craving for food, increased bowel and bladder activity, and thirst. Inhibitory symptoms include being withdrawn, mental slow down, behavioral sluggishness, feeling tired, difficulty focusing, slurred speech, difficulty finding the right word, poor concentration, slow thinking, asthenia, feelings of cold, anorexia, constipation, and abdominal bloating. In a study by Waelkens (64), such premonitory symptoms were classified under the headings of (a) general complaints, (b) symptoms related to the head, (c) abnormalities of eyes or sight, (d) sensory intolerance, (e) mood and behavior variations, and (f) abdominal symptoms. Children tend to have more abdominal symptoms, particularly pain as well as attacks of vertigo preceding their migraine headache without aura (43). In the various series reported so far (6,28,49,54,64,65) the incidence of premonitory symptoms has varied widely, from 7 to 88%.

Early studies of premonitory symptoms, however, lacked scientific rigor. In a recent study (23) of a selected patient population, the majority of whom had migraine without aura, prospective electronic diary documentation showed that tiredness (72%), difficulty with concentration (51%), and a stiff neck (50%) were the most common premonitory symptoms reported. The most reliable predictors, however, were yawning, difficulties with speech, difficulties with reading, and increased emotionality. Premonitory symptoms accurately predicted the onset of migraine headache within 72 hours 72% of the time.

Triggers (also called precipitating factors) are factors that, alone or in combination, induce headache attacks in susceptible individuals. Trigger factors precede the attack usually by less than 48 hours. This distinguishes them from aggravating factors. Triggers induce headache attacks in predisposed subjects and are not regarded as causal agents. Triggers are not universal. Moreover, the presence of a trigger factor does not always precipitate an attack in the same individual. This suggests a multifactorial trigger mechanism for individual attacks. One or more precipitating factors have been described in between 64 and 90% of patients with migraine (45,49,54,62), and overall they appear to be more common in patients with migraine without aura than in those with migraine with aura (49). The nature and frequency of the commonest precipitants are listed in Table 43-1.