Migraines are the sixth largest cause of years lost due to disability, and the third most common disease in the world — affecting around one in seven people. Most of us know people with migraines, or struggle with a migraine ourselves. When someone complains about their migraine, though, we tend to gravitate towards picturing them grappling with a debilitating headache. Rarely, if at all, do we hear about “silent migraines” — as harrowing and debilitating as a regular migraine, but without the characteristic raging headache.

“A silent migraine is when someone has the symptoms of a migraine without the head pain. It’s different from regular migraines because there is no head pain, but [doctors] have recently moved away from the term ‘silent’ because it can send the wrong message that it’s not as bad,” Dr. Bianca Barcelo, a neurologist and headache specialist, told Women’s Health. Dr. Barcelo prefers using the term, “migraine aura without headache,” instead. The condition is also called “acephalgic migraine.”

According to a 2015 study, silent migraines account for 3% of the migraines women experience, and 1% of those that men do. Regular migraines, too, affect women more — data by the NHS shows that they affect as many as one in every five women, but only about one in every 15 men.

The reason Dr. Barcelo used “migraine aura without headache” to refer to the condition is that researchers are beginning to treat aura and pain as two distinct, singular elements of migraines. With the pain being absent in a silent migraine, the symptoms can manifest as dizziness or vertigo, sensitivity to bright lights and loud noises, visual disturbances that include experiencing vision loss and tunnel vision while also seeing flashing lights and zigzag patterns, and trouble focusing to the extent that even carrying on a conversation can be challenging. Besides, some people can also experience a tingling sensation in their faces and limbs; they may also feel a sense of numbness settling in these parts. The day after the episode, one may also feel a sense of exhaustion akin to a hangover.

“I get zigzag lines. It’s the same colors every time — very intense blues, pinks, yellows, and black… I also get pins and needles, trouble speaking, [and] loss of feeling in my hands and my legs … Sometimes it’s so bad, I’ve got no ability to even walk… I get buzzing sounds like there are bees or wasps flying around my head,” a 27-year-old Zoe told The Guardian last year. “It just takes its toll, not being able to leave the house or do anything. I was struggling with depression at one stage.”

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In terms of more tangible physical symptoms, much like traditional migraines, the aura, too, can trigger nausea, vomiting, and sometimes, a stomach upset. It can also induce a sense of weakness in the body, accompanied by hot flashes and sudden chills, a stuffy nose, and a sore neck and jaw. In other words, just because migraines without headaches don’t seem as bad, doesn’t mean they aren’t incapacitating.

The lack of awareness can also make the symptoms alarming. “The first time it happened, I was about 14, and thought I was having a stroke or going blind — it was terrifying,” a 44-year-old Rachel had said in 2014. Initially, she consulted an optician, who assured her there was nothing wrong with her eyes. With about five attacks a year and no recourse in sight, she had to bear the temporary loss of vision and coordination for years. But somewhere around her late 30s and early 40s, they became more frequent — up to five times a day — promoting her to seek a doctor again. Now, she’s diagnosed. “For me, the aura is always the worst symptom, and while it is happening, there is nothing that you can do but wait it out.”

Unlike a regular migraine, which can last between four and 72 hours, a silent migraine usually lasts for about 15 to 30 minutes. It is generally over within 60 minutes of onset, at most. “As [a] wave [of electrical activity] spreads across the surface of the brain, each bit of the visual part of the brain is hit. The overactivity causes the flashing lights or the zigzags, and after that, you get a period of underactivity, and that’s where you get the blind spots. Eventually, that clears… all [one] needs to do is rest and let them pass,” explains Dr. Mark Weatherall, a neurologist and the vice-chair of the British Association for the Study of Headache. Dr. Weatherall says a migraine aura is akin to “a little tsunami, a wave of overactivity followed by a trough of underactivity.”

But again, the fact that it disappears rather swiftly, doesn’t necessarily make it less debilitating. On the flip side, its quick disappearing act makes it difficult to treat with medication. “Treatment can be difficult because many medications take longer to work than the actual symptoms [last]. You can try ibuprofen, but symptoms will probably be over by the time it kicks in,” Dr. Barcelo notes. Other over-the-counter medications like aspirin and acetaminophen, too, can be useful in managing the symptoms of silent migraines, but unfortunately, can kick in by the time one has stopped experiencing the symptoms.

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Not only that, but if a silent migraine comes on while a person is operating heavy machinery, or even just driving on a busy street, it could be deadly. “For a patient who has [a] visual aura that comes on in situations like driving, it can be very disconcerting. It affects day-to-day functioning, even if headache[s] and other features [associated with regular migraines] aren’t there. This is especially true if it’s the first time it happens, or [if suddenly] there’s a change in how [a person’s silent migraine customarily] presents,” Dr. Jennifer Robblee, a neurologist and headache specialist, explains. “Migraine aura[s] without headache can be quite scary.”

The relative ineffectiveness and side effects of prescription medicines aside, alternative treatments like massage therapy, acupuncture, and biofeedback might make silent migraines more manageable by reducing stress, which can be a trigger for episodes of silent migraines. Besides stress, hunger, extreme changes in the weather, too much or too little sleep, excessive sensory stimuli, and strain on the eyes or the neck can elicit an episode, too. Some easier-to-control triggers also exist — like alcohol, caffeinated beverages, and fermented and pickled foods. A family history of migraines, or undergoing menstrual changes, can make one more vulnerable to silent migraines.

The means for diagnosing silent migraines include blood tests, spinal taps, and CT or MRI scans. However, diagnosing them can be tricky because they lack the hallmark symptom of a headache. It is easily misdiagnosed as a stroke or ministroke, an instance of bleeding in the brain, meningitis, or even epilepsy. And, sometimes, what seems like a silent migraine could indeed be any of those; in fact, suffering from migraines — with or without headaches — can increase the risk of one having a stroke. This is precisely why experts advise against self-diagnosing a silent migraine.

“Unfortunately, silent migraines are very difficult to diagnose and treat because it’s a little bit of an exclusion to make sure it’s not anything else… Any time that you have symptoms that are interfering with your life and quality of life, then it’s a good time to see a neurologist,” Dr. Barcelo advises. “All migraines are a thief of time and patience, so advocate and make sure you talk with your primary care doctor or a neurologist about your headaches — or lack thereof — so you can live your best life.”