Migraines are often associated with colourful visual disturbances called auras, but many mysteries remain about how they fit into the wider biology of the syndrome.

In 2012, neurologist Andrew Charles received a phone call from a septuagenarian engineer who had begun having migraines with aura at the age of 14. The man, who asked to be identified as P.V., told Charles that for the previous 18 years he had been drawing every single aura he had experienced — an average of 80 per year.

Whenever he sensed an aura beginning, P.V. grabbed a sheet of paper and sketched what he saw. With an engineer’s meticulousness, he ran a stopwatch and redrew the shifting mirage every minute until it ended, typically 25–30 minutes later. He asked Charles whether his drawings might be useful to scientists interested in migraine. Soon after, P.V. arrived in Charles’s office at the David Geffen School of Medicine at the University of California, Los Angeles, and deposited a thousand-strong stack of papers on the desk.

P.V.’s auras began as a small focal disturbance, which then expanded into a slowly spreading, crescent-like shape. The leading edge of this crescent was a flickering, morphing band of zigzagging, multicoloured lines known as a fortification spectrum. In the spectrum’s wake was an area of diminished vision called a scotoma.

Transient neurological disturbances such as these are typical of auras. More than 90% affect vision, but symptoms can take various other forms, including tingling or numbness around the body and an impaired ability to speak.

Auras are widely viewed as a hallmark of migraine, but they remain an enigmatic phenomenon. Research has focused on suppressing the debilitating pain of migraine headaches. How the short-term neurological features of auras relate to headaches and other aspects of migraine remains uncertain. Some researchers think that auras cause headaches; others posit that they are just another aspect of a multifaceted syndrome.

A major challenge of pinning down auras is their inconsistency. They regularly affect only around 20–40% of people with migraine, and for many of them, not every headache has an accompanying aura. Also, many people experience auras without getting headaches.

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