What is Migraine Aura?
Migraine is an electrical neurological event that happens in the brain, and is one of the most common neurological conditions. For those 30% that get the neurological symptoms of migraine aura preceding their headache, it can be very scary, mimicking stroke symptoms or TIA (transient ischemic attack). Migraine aura most often consists of visual, sensory, and speech neurologic symptoms occurring prior to a migraine headache attack, lasting 5-60 minutes. Migraine aura is caused by a slow moving electrical wave that spreads across the outside of the brain (cortex). Depending on where this wave spreads dictates the type of aura you experience.
Typical migraine aura visual symptoms preceding the severe headache of migraine are visual loss, shapes, colors, shapes, scintillating scotomas, blind spots, bright lights, shimmering or flashing lights, entoptic phenomena, or other visual disturbances. Visual symptoms are most common and may affect part of the vision or the entire visual field. Sensory aura presents with numbness and/or tingling on one side of the body (face and arm most commonly involved), and sometimes around the mouth. Speech (dysphasia) aura presents with trouble getting words out, slurred speech, or sometimes speech comprehension. There are other less common types of aura such as motor aura (previously called hemiplegic migraine) which causes weakness on one side of the body, and migraine with brainstem aura (previously called basilar migraine) which causes a mix of neurological symptoms.
By criteria, visual, sensory, or speech aura should last 5-60 minutes and not longer and usually precede the migraine attacks. Motor aura (hemiplegic migraine) symptoms can last up to 3 days. However, there are more rare aura phenomena where visual aura symptoms persist and do not stop. One of the most frustrating forms of persistent migraine aura is called visual snow syndrome. The other is status aura, manifesting as the person’s usual aura symptoms, but they don’t “shut off”, and persist.
Even more rare than persistent migraine aura is migrainous infarction (stroke), which is stroke that occurs during a migraine, at a location in the brain which correlates to their aura symptoms.
What Causes Migraine Aura?
The understanding of migraine has evolved from the vascular theory to the neurovascular theory of migraine. In other words, we now look at migraine as an electrical event, not a vascular (blood vessel) event in the brain. The older vascular theory of migraine assumed that during a migraine there was initially blood vessel vasospasm (narrowing) causing lack of blood flow to areas of the brain (similar to stroke or TIA). It was felt that this lack of blood flow was the cause of the neurological (aura) symptoms (from ischemia, or lack of blood flow). It was believed that this was followed by blood vessel dilation (widening) leading to excess blood flow to the area and the throbbing migraine pain. This is why migraine was called a “vascular headache” for many years. However, in later migraine studies, aura symptoms were found to actually be due to a transient period of decreased brain metabolism rather than true ischemia from lack of blood flow.
Karl Lashley, a Harvard psychologist, first described and mapped his own visual aura in 1941. He hypothesized that the aura was due to a spreading abnormality moving across the visual cortex at a rate of 3-5 mm per minute. In 1944, a neurophysiologist named Aristides Leão confirmed Lashley’s hypothesis. He showed a phenomenon called cortical spreading depression in an animal model. It starts as an electrical wave following a burst of neuronal overactivity and hypermetabolism. This electrical wave is associated with increased blood flow to this area (neurons need extra blood flow to send glucose and oxygen to work, especially when overactive). Following this electrical wave and neuronal overactivity, there is a longer lasting wave of neuronal electrical suppression (depressed activity) with decreased blood flow (neurons are now metabolically underactive, so do not need as much blood flow).
This phenomenon is the basis for migraine aura. At the front of this spreading electrical wave, the neurons are in a state of hypermetabolism, requiring an increase in blood flow. This hypermetabolism causes the positive symptoms of migraine aura (colors, flashing lights, kaleidoscope, shapes, zig-zags, tingling sensory changes, etc.). Following this electrical wave there is “neuronal depression” and decreased neuronal metabolism, associated with a decrease in blood flow. This hypometabolism causes the negative symptoms of migraine aura (loss of vision, black spots, numbness, etc.). So the lack of blood flow in the area of cortical spreading depression is not due to true ischemia (such as from a spasming or blocked artery). It is due to a transient period of very low brain metabolism and thus a lower need for blood flow to that area to deliver glucose and oxygen to inactive neurons.
Depending on where this wave spreads, you may get different aura symptoms; visual aura as it spreads across the occipital (visual) cortex, sensory/numbness/tingling as it spreads across the parietal (sensory) cortex, dysphasia (trouble speaking, slurred speech) as it spreads across the frontotemporal (speech) cortex, one sided weakness in hemiplegic migraine as it spreads across the frontal (motor) cortex, brainstem symptoms such as vertigo, tinnitus, double vision, hearing loss, imbalance, decreased level of consciousness, slurred speech (previously called basilar migraine, now called migraine with brainstem aura) as it spreads across the brainstem.
What is Visual Snow Syndrome and Persistent Migraine Aura?
Normally, migraine aura symptoms last 5-60 minutes and then the wave of cortical spreading depression resolves and the neurons come back to normal metabolism. However, infrequently the aura symptoms persist and do not shut off. The ICHD-3 diagnostic criteria defines persistent migraine aura without infarction (stroke) as aura symptoms persisting for 1 week or more without evidence of infarction (stroke) on neuroimaging. It should occur in a patient with a history of migraine with aura and typical of previous auras except that one or more aura symptoms persist for 1 week or more. Neuroimaging must show no evidence of infarction (stroke). The aura symptoms may last for months or years.
There are two primary types of persistent migraine aura, and both can lead to significant visual impairment. One is persistent primary visual disturbance in which the patients describe “visual snow” visual static or “television static” in both visual fields in both eyes, and some report additional intermittent scotoma or oscillating lights. The other is persistent migraine aura with typical aura, in which patients describe scotoma, fortification, or oscillation in one hemifield (one side of vision), and it does not go away (sometimes also called status aura).
What Causes Visual Snow Syndrome and Persistent Migraine Aura?
The exact cause of visual snow syndrome and persistent migraine aura remains unknown, although several theories exist. Some of these theories include low cerebral magnesium levels, abnormal cerebral energy metabolism, greater cerebral reactivity of NMDA receptors to glutamate, lower threshold for triggering cortical spreading depression, low cortical preactivation due to thalamocortical hypoactivity, sustained hyperexcitability of the visual cortex without significant dynamic modulation, sustained cortical neuronal dysfunction, impaired visual processing, intracortical disinhibition, glutamatergic dysregulation and impaired sensory gating, loss of inhibitory GABA-ergic interneurons resulting in a network imbalance leading to a reverberating cycle of cortical spreading depression, or a combination of these.
What Tests Are Done for Visual Snow Syndrome and Persistent Migraine Aura?
The evaluation for persistent migraine aura without infarction should focus on excluding stroke, brain tumors, or other pathological causes. Brain MRI and MRA should be checked. If MRI is not possible, brain CT and CTA should be considered. Contrast administration for either type of scan is preferred, but not mandatory. A detailed neuro-ophthalmologic examination (or at least a dilated eye exam with an ophthalmologist) is also required. An ESR, CRP, TSH, CBC, CMP should always be done, and additional labs depending on the history and other symptoms. I also like to add a hypercoagulation panel with any atypical or prolonged aura symptoms, as well as in hemiplegic migraine (motor aura) and basilar migraine (brainstem aura). An EEG should also be considered to exclude seizures coming from the occipital lobe (visual cortex). Depending on the specific history and symptoms, there may be additional testing performed as well.
What are the Treatments for Visual Snow Syndrome and Persistent Migraine Aura?
Treatment for persistent aura and visual snow is can be a frustrating trial and error process of trying different options. Treatments and medications used are all the same as those used for typical migraine preventative measures. Many have been studied in visual snow syndrome, but the vast majority have shown no evidence of benefit. Of them, the anticonvulsants generally are felt to be the most likely to potentially help given that these medications are targeting the electrical system, and persistent aura symptoms are an electrical phenomenon. Lamotrigine has shown the most evidence of benefit overall of the medications, although evidence is limited. Regardless, it is generally considered a first line treatment for visual snow syndrome. Vitamins (such as magnesium) and benzodiazepines have shown some benefit, but long term use of benzodiazepines should be avoided. I generally also like to have patients on a baby aspirin 81 mg daily unless there is a medical contraindication to it.
Of the neuromodulation devices, the SAVI Dual repetitive transcranial magnetic stimulation (TMS) device theoretically could be a good consideration. It delivers a TMS pulse to the occipital cortex in the back of the head, where the source of the persistent visual aura and visual snow are felt to originate from. I like to think of the neuromodulation devices as electrically rebooting the circuitry. Anecdotally, I have seen a couple cases that did receive improvement in symptoms after a treatment trial in the office with SAVI Dual.
Nonpharmacological treatments include chromatic filters (tinted lenses) and migraine glasses such as Avulux. Chromatic tints showed a mean subjective reduction of visual snow symptoms by 45%, with some patients reporting up to 100% improvement. Neuro-optometric visual rehabilitation therapy (NORT) has shown subjective improvement in symptom reduction and improved quality of life. Overall, chromatic tints and oculomotor training appear to be the most successful of all types of visual snow treatments. Mindfulness-based cognitive therapy (MBCT-vision) has shown benefit in symptom severity and quality of life. Environmental modifications, such as minimizing exposure to indoor and fluorescent lighting and use of migraine glasses may also reduce symptom burden.
For those that still get migraine headache attacks, abortive migraine options can include the gepants (Ubrelvy, Nurtec, Zavzpret), ditans (Reyvow), neuromodulatory devices, and NSAIDs/over the counter analgesics. Triptans and ergots such as DHE (dihydroergotamine) should be avoided due to potential stroke risk when used during prolonged aura symptoms.
Migrainous Infarction (Stroke)
The ICHD-3 defines migrainous infarction as one or more migraine aura symptoms associated with an ischemic brain lesion in a correlating anatomical clinical territory demonstrated by neuroimaging. It should occur in a patient with a history of migraine with aura and typical of previous attacks except that one or more aura symptoms persists for more than 60 minutes. Clearly associating an ischemic stroke and a migraine attack in a migraine sufferer can be difficult. Stroke from other causes can coexist with migraine, and can present with symptoms resembling migraine with aura. Or stroke can occur during an attack of migraine with aura, and this is the only scenario that would be consistent with migrainous infarction.
Migrainous infarction occurs predominantly in the posterior circulation and in younger women. In the Cerebral Abnormalities in Migraine, an Epidemiological Risk Analysis (CAMERA) study, these infarct-like white matter lesions found in migraine patients (primarily in migraine with aura) were predominantly located in the posterior circulation, especially in the cerebellum. However, these infarctions are not necessarily considered migrainous infarctions and the mechanisms are unclear.
The evaluation for migrainous infarction is similar to that of persistent migraine aura without infarction. By definition, an ischemic infarct from a blood clot in a correlating anatomic area to symptoms should be seen on MRI or CT of the brain. This warrants a further standard stroke evaluation, including imaging of the intra and extracranial vasculature (including carotid arteries), as well as cardiac evaluations beginning with transthoracic echocardiography. Electrocardiogram and telemetry should also be pursued to evaluate for paroxysmal arrhythmias such as atrial fibrillation, which is a heart rhythm associated with a much higher risk of stroke.
Some theorized mechanisms of migrainous infarction include vasospasm, endothelial dysfunction, vascular endothelium-related hypercoagulability (tendency to form blood clots easier) during cortical spreading depression and the aura phase, open patent foramen ovale, or genetic alterations of the wall of the small cerebral arterial vessel walls.
Treatment of migrainous infarction is the same as with any ischemic stroke acutely and preventively. The initial goal is to quickly evaluate for potentially treatable and reversible etiologies of stroke (such as cardioembolic source) and treat accordingly with intravenous “clot buster” treatments in the emergency room if blockage is seen on imaging, and if patient is still within the treatment window. Otherwise, secondary stroke risk factor modifications are the goal and include antiplatelet therapy in combination with optimal control of blood pressure, hypertension, hyperlipidemia, diabetes, tobacco/smoking cessation, and healthy lifestyle changes.
Abortive migraine options can include the gepants (Ubrelvy, Nurtec, Zavzpret), ditans (Reyvow), neuromodulatory devices, and NSAIDs/over the counter analgesics, although triptans and ergots (DHE) should be avoided.
Does Migraine With Aura Increase Your Risk Of Stroke Or Heart Attack?
Multiple studies have confirmed the association with increased stroke risk in women with migraine with aura. Women younger than age 45 who have migraine with aura, have a 2 fold increased higher risk of ischemic stroke. Notably, migraine without aura does not appear to have the same increased risk. This risk increases to 6 fold in the setting of oral contraceptive use containing estrogen, and more than 9 fold with combined smoking and oral contraceptive use. 24 Menstrual migraine and the use of hormonal therapy and birth control is discussed in more detail here.
Women who are smokers and have migraine with aura should consider estrogen containing oral contraception a contraindication. The use of hormonal contraceptives containing estrogen in non-smoking women with migraine with aura is more controversial. The World Health Organization (WHO) and American College of Obstetrics and Gynecology (ACOG) suggest that in non-smoking women under age 35 with migraine with aura, there is an acceptable lower risk of oral contraceptive use. However, if they are over age 35, the risk is unacceptably higher and oral contraceptive use is contraindicated.
According to the International Headache Society (IHS), in non-smoking women with migraine with aura who are either younger or older than age 35, taking into account other risk factors should individualize the decision for oral contraceptives. These would include ischemic heart disease, family history of early heart disease at a young age of less than 45 years old, heart disease with concern for emboli such as atrial fibrillation, uncontrolled hypertension, hyperlipidemia, diabetes, obesity, systemic disease associated with increased stroke (connective tissue disease, sickle cell, hypercoagulability), etc. In women with an increased risk of stroke, and especially with multiple vascular risk factors, non-estrogen methods of birth control such as progesterone-only forms of contraception should be recommended.
One study reported that after high blood pressure, migraine with aura was the second strongest single predictor of heart attack and strokes, ahead of diabetes, smoking, obesity, and family history of early heart disease. This increased risk was not seen in migraine without aura. It is not necessarily thought that migraine with aura causes the stroke, but rather it is a marker for young women at a greater risk for cardiovascular disease (CVD). However, the reasons for these associations are unclear, likely multifactorial, and clearly need to be further defined. Traditional vascular risk factors such as hypertension, smoking, diabetes and hyperlipidemia still show the strongest contribution to cardiovascular disease, so these should be optimized, especially in those with migraine with aura to reduce risk of both heart disease and stroke.
Another larger follow up study evaluated the association of migraine with aura and other vascular risk factors with major CVD events (stroke, heart attack, death due to cardiovascular disease) in women aged 45 years or older. Women 45 years or older who had migraine with aura had a higher rate of CVD compared to women who had migraine without aura or no migraine. Basically, they looked at the likelihood of having heart attack or stroke if you have migraine with aura and compared the risk with a number of individual vascular risk factors which included diabetes, current smoker systolic blood pressure 160 mm Hg or higher, total cholesterol 280 mg/dL or higher, HDL cholesterol less than 40 mg/dL, triglycerides 194 mg/dL or higher, family history of heart attack prior to age 60 years old, and body mass index (BMI) of 30 or more.
Results showed that compared to having migraine with aura, only 2 other individual risk factors led to a higher incidence rate of major CVD; diabetes and current smoking. Women with migraine with aura had a similar risk of major CVD as those with high blood pressure, high total cholesterol, and family history of heart attack. Furthermore, adding migraine with aura to each individual risk factor led to a significantly increased risk of major CVD compared to having the vascular risk factor alone. These significant increases in CVD risk were associated specifically to migraine with aura, not migraine without aura.
These studies highlight the importance of optimizing medical treatments for vascular risk factors which lead to heart attack or stroke, especially in the setting of having migraine with aura.
Conclusions
Migraine aura is a fascinating electrical phenomenon in migraine, which is one of the most common neurological disorders. However, it can be scary for those 30% of migraine patients who experience aura, especially when it first occurs. Migraine aura can resemble symptoms of a stroke or TIA, so it is important to get seek emergent medical attention if it is a completely new symptom for you. Migraine aura can less commonly cause persistent migraine aura symptoms, including visual snow syndrome. These persistent aura symptoms are known to be more resistant to typical migraine treatments, but there are many treatment options to try. Very rarely, migraine aura can be associated with stroke. Avoiding risk factors for migrainous stroke such as estrogen use with smoking, high blood pressure, high cholesterol, diabetes, and smoking can lessen the risk of stroke associated with migraine.
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