Written and medically reviewed by Tae Ho Guak, MD, board-certified neurologist · Reviewed July 2026 · Editorial policy
A 58-year-old engineer came to see me last spring, holding a printout of a normal head CT from the emergency department. Two weeks earlier, mid-meeting, a small shimmering spot had appeared just left of center in his vision. Over about ten minutes it grew into a flickering crescent with jagged edges that drifted slowly toward the edge of his field, leaving a blurred hole behind it. Twenty-five minutes in, it was gone. No headache. He had spent the two weeks since convinced he had a stroke and was waiting for the next one.
He had migraine aura without headache — a migraine attack that produces the neurological phase and then simply never becomes pain. It has a formal name in the international classification (ICHD-3 1.2.1.2, typical aura without headache), and the features that identify it are quite specific: a visual disturbance that builds over five minutes or more, drifts or marches across the visual field, has bright or shimmering positive features rather than only darkness, and resolves completely within an hour. What makes me stop and investigate instead is the opposite pattern — sudden, complete at onset, purely a loss of vision, confined to one eye, or happening for the first time after age 50. Those need a vascular workup, not reassurance.
What migraine aura actually looks like when you watch it closely
The single most useful question I ask is not what the patient saw but how it arrived. Migraine aura is a slow-moving wave of cortical activity, and it behaves like a wave. It starts small — patients describe a speck, a smudge, a spot where a word on the page has gone missing. It expands. It moves. The classic form is a scintillating scotoma: a C-shaped or crescent-shaped arc of flickering, sometimes colored zigzags, brightest at its leading edge, with a blind or blurred area trailing behind it. Over fifteen to thirty minutes it drifts outward toward the periphery and disappears.
Two details matter more than people expect. First, migraine aura is nearly always positive before it is negative — you see something that isn’t there (light, sparkle, shimmer, heat-haze distortion) before you lose part of the field. Vascular events overwhelmingly do the reverse: they take vision away without adding anything.
Second, the disturbance is in a visual field, not an eye. Aura arises in the occipital cortex, so it affects the same side of the visual field of both eyes. Almost every patient tells me it was in their left eye or right eye, because that is how it feels. When I ask whether they covered each eye in turn to check, hardly anyone has. That one test — cover one eye, then the other, next time it happens — separates a cortical event from an eye or retinal problem better than most of the tests I can order.
If the visual symptom is followed by tingling that creeps from the fingers up the arm to the face over several minutes, or by difficulty finding words, that sequential march across different symptom types is close to diagnostic of migraine aura. Blood-vessel events do not politely queue up one after another.
The pattern that makes me think vascular rather than migraine
A transient ischemic attack is abrupt. It is maximal at the very first second. There is no build, no expansion, no march. It is usually a loss — a grey curtain, a dark half-field, a blank area — with nothing bright about it. Amaurosis fugax, the classic transient monocular blindness of carotid disease, really is one eye, and the cover test proves it.
These features put me on the vascular side rather than the migraine side. Onset that is instantaneous and complete rather than gradual. Symptoms that are purely negative — vision gone, arm dead, no sparkle or tingle first. A deficit confined to one eye. Duration well beyond an hour, or a deficit that has not fully cleared. Weakness on one side, or slurred rather than word-finding speech trouble. A first-ever episode in someone over 50, particularly alongside high blood pressure, atrial fibrillation, diabetes, or a smoking history. And a stereotyped, identical episode recurring several times within days, which is a pattern that worries me considerably more than it usually worries the patient.
One caveat I want to be honest about: weakness during an attack is not automatically vascular. Hemiplegic migraine causes genuine one-sided weakness as part of the aura, and it can last hours. But it is uncommon, it often runs in families, and it is not a diagnosis anyone should assume on a first episode. Weakness with a headache attack earns imaging, not reassurance.
Why aura can arrive without headache later in life
The version of this I see most often is a person in their fifties or sixties who had migraine with aura in their twenties and thirties, lost the headaches somewhere along the way, and now gets the aura on its own a few times a year. The headache phase drops out with age in a substantial number of people; the aura phase does not. When there is a clear personal history of the same visual phenomenon decades earlier followed by pain, and nothing about the attack has changed except that the pain stopped coming, I am comfortable.
The harder situation is aura appearing for the first time after 50 in someone with no migraine history at all. Neurologists call these late-life migraine accompaniments, and they are real — but that label is one of exclusion. A first aura at 62 gets a proper vascular assessment: MRI with diffusion sequences rather than CT alone, imaging of the carotid arteries, an ECG with rhythm monitoring to look for atrial fibrillation, and often an echocardiogram. Only when that is clean and the attacks keep behaving like aura do I settle on migraine.
A normal CT in the emergency department, as my engineer discovered, does not close this question. CT is very good at finding bleeding and quite poor at finding a small recent infarct. I have written separately about what a normal scan does and doesn’t rule out — the same logic applies here, and more so for CT.
What I do about it once the diagnosis is settled
For most people, less than they expect. Aura is self-limited and does not respond to acute migraine drugs; triptans are aimed at the headache phase, and taking one during the visual phase does not shorten it. If there is no pain to treat, there is often nothing to take. What helps more is knowing what it is, so that thirty minutes of flickering lights stops being thirty minutes of fearing a stroke.
If attacks are frequent — more than a few a month, or disruptive enough to interfere with driving and work — I treat it as I would any migraine needing prevention, and the same preventive options apply. Aspirin is not an automatic prescription here; it treats a vascular diagnosis I have just spent the visit ruling out.
There is one decision I never leave unaddressed. Migraine with aura, including aura without headache, roughly doubles ischemic stroke risk, and combining it with estrogen-containing contraception multiplies that risk several-fold. Any woman I diagnose with aura leaves my clinic knowing that combined oral contraceptives are off the table and that progestin-only options exist. The details are in my piece on migraine with aura and stroke risk. Smoking and untreated blood pressure belong in the same conversation.
My engineer has had four more episodes since. He knows the shape of them now, he covers one eye out of habit to confirm it is both, and he no longer drives while one is happening. That is the whole of his treatment, and it is enough. If your own visual episodes have never been properly explained, or the explanation has never quite fit what you experience, that gap is worth closing — I’ve written about why headaches and headache-related symptoms go misdiagnosed for years and when a second opinion earns its keep. And if your episodes come with spinning or unsteadiness rather than pain, vestibular migraine is a different chapter of the same book.
Not sure whether your symptoms need urgent assessment? Start with the free Headache Red Flags Checklist — the warning signs I check for in every new patient.
Want it looked at properly? You can talk to a specialist about your case.
Dr. Tae-Ho Guak, MD, is a board-certified neurologist with 25 years of practice and more than 100,000 patient consultations.
This article is for education and does not replace an in-person medical evaluation. Sudden severe headache peaking within a minute, weakness or numbness on one side, difficulty speaking, sudden vision loss that does not resolve, or a first-ever neurological episode after age 50 require immediate emergency assessment — go to an emergency department now.
From the textbook. Chapter 9, “Migraine With Aura and Its Subtypes,” of my clinical textbook Headache Medicine covers this topic in full for doctors, with the evidence and decision pathways behind it. About the book →