Migraine aura

How it works

An aura starts as a small blind or flickering spot near the centre of vision. Over minutes it spreads outward. Its edge becomes a zigzag of bright, shimmering lines, often shaped like a C or a crescent². Behind the edge is a blank patch. The whole thing lasts 5 to 60 minutes and then fades⁴. It looks the same with either eye closed, because it is in the brain and not in the eye². Other auras exist: tingling that creeps up an arm, or trouble finding words¹.

The cause is cortical spreading depression. A wave of intense neuron activity, followed by silence³, moves across the visual cortex at about 3.5 mm per minute⁶. Where the wave is, you see flicker. Behind it, where the neurons are quiet, you see a blank⁶. The slow speed of the wave explains the slow growth of the pattern.

About 5% of people have migraine with aura at some time in their life⁵. About 30% of people with migraine get aura⁴. In some people the aura comes with no headache at all. In many people this starts later in life². The name “ocular migraine” is used loosely, so doctors prefer “migraine with aura”.

Is it a problem?

Usually no. An aura does not damage the brain or the eyes. It passes within the hour. Do not drive during it.

Get a first episode checked, because a doctor should confirm that it is an aura and not something else.

Go to emergency care if the episode:

• lasts more than an hour,
• starts suddenly at full size rather than spreading,
• comes with weakness on one side,
• comes with trouble speaking,
• comes with the worst headache of your life.

Those can be a stroke, which looks similar but begins all at once.

Once a doctor has confirmed typical aura, repeat episodes do not need emergency care. Tell your doctor if the pattern changes. If you use a combined hormonal contraceptive, mention the aura, because the two together raise stroke risk⁴.

History and culture

The zigzag edge is called “fortification spectra” because it looks like the walls of a star-shaped fort seen from above². The visions described by the 12th-century abbess Hildegard of Bingen, which she called “reflections of the living light”, may have been migraine auras⁴.