Aura has long been a perplexing issue in migraine. Primarily viewed as a prodromal sign of migraine in some patients some of the time, aura has been largely overlooked in clinical trials that tend to enroll patients with migraine with and without aura.1 However, new evidence increasingly points to migraine with aura as a separate entity from migraine without aura, with important pathologic differences.
The most recent definition of migraine aura by the International Classification of Headache Disorders-3 (ICHD-3) is from 2018,2 and cites “recurrent attacks, lasting minutes, of unilateral fully reversible visual, sensory, or other central nervous system symptoms that usually develop gradually and are usually followed by headache and associated migraine symptoms.”
As many as one-third of patients with migraine may experience aura (prevalence estimated at 20%-40% of all people with migraine), although most do not experience aura with every migraine.1,3 The clinical manifestation of auras varies among patients, and between attacks in the same patient. Most (99%) patients experience visual distortions at least some of the time, as well as sensory, speech/language, motor function symptoms, and alterations of cortical function.1
Migraine with aura has not been well studied compared with migraine without aura, and participants with both types of migraine are generally accepted into the same clinical trials.1 This may be in large part because there is a lower prevalence of migraine with aura, but also because of the difficulty of examining the aura event itself.4
Although patients with aura are more likely to be referred for computed tomography scanning, images rarely capture aura, as researchers have yet to find a dependable means to predict or trigger the phenomenon.5-7 In addition, the short duration of auras (usually lasting <60 minutes) prevents the opportunity to obtain a scan when the event occurs.4
Among imaging studies that have been done, white matter abnormalities were detected at 4 times the rates in patients with total migraine compared with the general population, but no significant differences in structural brain changes were observed between migraine with aura and migraine without aura.1 Early studies did show differences in blood flow dynamics between the 2 types of migraines.4,7