Aura is a brief neurological event — typically 5 to 60 minutes — that precedes or sometimes accompanies a migraine attack. It is a distinct phase from the prodrome (which is hours to days before) and from the headache itself. Aura affects roughly 25–30 percent of people with migraine, divided fairly evenly between visual, sensory, and (less commonly) language aura.
The neurological substrate is cortical spreading depression — a slow-moving wave of altered electrical activity across the cortex, traveling at roughly 3 mm/minute, which produces the characteristic gradual onset and march of symptoms.
The most common forms
Visual aura (most common, ~90% of aura cases)
- Scintillating scotoma — a crescent-shaped blind spot with a shimmering, zigzag border that expands across the visual field over 20–30 minutes.
- Flashing lights in part of the visual field.
- Zigzag lines (sometimes called “fortification spectra” because the pattern resembles old fortress walls).
- Blind spots that gradually expand and then resolve.
Visual aura typically affects both eyes (it’s a cortical phenomenon, not retinal), but patients often perceive it as one-eyed.
Sensory aura (~30% of aura cases)
- Tingling or numbness that spreads gradually across a body region — often starting in the fingertips, marching up the arm to the face over 10–20 minutes. The gradual spread is characteristic and helps distinguish from sudden stroke symptoms.
Language aura (less common)
- Word-finding difficulty (transient aphasia).
- Difficulty understanding speech.
- Speech that comes out garbled or doesn’t make sense to the speaker.
Language aura is uncommon enough to be alarming the first time it happens; many patients fear they’re having a stroke.
Aura vs prodrome — a frequently confused pair
| Feature | Prodrome | Aura |
|---|---|---|
| Timing | 2–48 h before headache | 5–60 min immediately before / during |
| Duration | Hours, sometimes days | Minutes |
| Symptoms | Systemic (fatigue, mood, cravings) | Neurological (visual, sensory, language) |
| Mechanism | Hypothalamic / brainstem changes | Cortical spreading depression |
| Prevalence | ~60–70% of migraine | ~25–30% |
The two can coexist in the same person. A prodrome the evening before can be followed by visual aura the next morning, then the headache.
Aura without headache
“Aura without headache” (or “acephalgic migraine”, or “silent migraine”) is a recognised ICHD-3 diagnosis. The aura still occurs — same visual or sensory or language symptoms — but the headache either doesn’t develop or is so mild it’s barely noticed. This pattern is more common in people over 50 and can be the first presentation of migraine in older adults.
If you experience aura without headache, the ICHD-3 criteria still require the aura to fully resolve (within 60 minutes for typical aura) and a prior history of migraine attacks. A first-ever aura-like event after age 50 needs neurological evaluation to rule out other causes.
When aura needs urgent evaluation
Most aura is migraine. But specific patterns warrant immediate medical attention:
- Sudden onset rather than the typical 5–20-minute gradual build.
- Symptoms lasting longer than 60 minutes.
- Weakness (not just numbness or tingling) — this could be a variant called hemiplegic migraine, which has different management.
- First aura ever after age 50.
- Aura with persistent neurological deficit after the typical resolution window.
These can signal stroke, TIA, or rarer conditions. Migraine forecast apps are not useful here; emergency department evaluation is.
What Hermly does and doesn’t do
Hermly does not detect aura — there’s no sensor that picks up cortical spreading depression on a consumer device. The risk forecast applies to migraine days generally, not to specific phases like aura.
If your migraine pattern includes aura, the patterns Hermly can help with are the same as for migraine without aura: identifying trigger windows, tracking attack frequency, and producing structured data for clinical visits.
The treatment of migraine with aura includes some specific considerations — combined hormonal contraceptives are contraindicated in women with migraine with aura, for example, due to stroke risk. That’s a conversation for a neurologist or gynaecologist, not for Hermly to navigate.