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Could Your Headache Be Dangerous? 5 Signs To Watch For

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Of all the aches and pains I spend my days investigating as a family doctor, none seem to be as anxiety-provoking as a headache. And that's often true, both for patients wondering, "Could this be something dangerous?" and for clinicians trying to get to the root of pain that can be totally unexplained and yet completely debilitating.

Concerns about headaches in my practice have picked up over the past year as we've seen them as a symptom in acute COVID-19 infections and among long-haulers — and more recently when news broke about the (very, very few) brain clots linked to the Johnson & Johnson vaccine.

Though we're all one Google search away from assuming a worst-case scenario when a headache strikes, the odds are overwhelmingly in our favor here. Research shows that the vast majority of headaches are what's known medically as "primary," meaning they're not the result of some other underlying condition. In other words, your headache is unlikely to be caused by a serious or life-threatening problem.

Dangerous headaches also tend to have some distinctive features and patterns – and they can be hard to ignore. Here's an overview of those red flag symptoms, and when you need same-day or emergency care:

The worst headache, in no time flat

You may have been told to be wary of a sudden headache, but just how sudden does it have to be to be a red flag? It's a lot quicker than you'd think.

We're talking in terms of seconds – the headache comes on fast with an intensity that stops you in your tracks, feels downright unbearable, and the pain peaks within less than a minute or so (although the headache may continue for longer). This is called a thunderclap headache, and patients tend to describe it as explosive, or "the worst headache I've ever had."

Mia Minen, a neurologist and chief of headache research at NYU Langone Health, says it's like "the snap of the finger: 10 out of 10 pain."

That stands out from a typical headache that tends to creep up over several minutes or an hour, linger a while and get worse as time wears on. Even though other non-life-threatening headache syndromes such as migraineor cluster headaches might still usher in the same pain intensity, those tend to build more gradually or may even be preceded by an aura (sensory symptoms such as tingling or spots in your vision).

Thunderclap headaches are a sign of something serious until proven otherwise, given their link to brain bleeds — things such as ruptured aneurysms or other hemorrhages, though they can be related to other masses or lesions in the brain as well.

Do not delay medical care with a headache such as this – it's an emergency, so call 911 or have someone help you to an emergency room. That is true for people of any age, with or without a history of headaches, and whether or not it's accompanied by other symptoms such as vomiting or passing out.

Nervous system symptoms

My patients and their families will tell you I often belabor the same list of stroke symptoms that we all need to be ready to recognize early. If a headache accompanies one of these symptoms, don't stop to think about the timing or severity, or really anything at all regarding that headache – just call 911.

The list of symptoms to watch for includes: abrupt weakness overall or in an arm or a leg, new numbness, changes in speech, confusion or trouble understanding and expressing thoughts clearly, facial droop or sudden trouble walking. It's also critical you get immediate care for changes in consciousness such as difficulty waking up, being in a stupor, passing out or having a seizure.

Changes from motion

This next group of symptoms deserve same-day attention by your primary care provider. If you don't have one, or can't get a prompt appointment, go to an urgent care clinic.

One of the most important questions they will ask you about the headache is what's making the pain better or worse. Take notice if the ache sharpens intensely with day-to-day movements — things such as bending over, rolling over in bed or even bearing down when you're having a bowel movement.

And along the same lines, it may not be an ordinary headache if the pain gets much worse when lying flat and better with sitting or standing. We call that a "postural" headache, and it can be a sign of masses putting pressure on the brain or spinal cord, and has been known to happen with blood-clotting events in the brain. This type can also present as a new morning headache that's severe and might come with vomiting.

There's a familiar alternative to this: a headache that gets subtly worse standing up and is better lying down. This can be an indicator of dehydration (or low blood pressure, often caused by dehydration and medicines, among other things). It's really no different than a hangover headache, though I hear complaints of this all the time from patients who admit they live off dehydrating drinks such as coffee or soda. Fortunately there's a quick fix: Drink more water.

But if this type of pain pattern is particularly pronounced with a dramatic increase in pain when you stand up, or you can't reasonably attribute it to being a little dehydrated (i.e., thirsty, with dry lips and scant or darker urine), it's important to get checked out.

Stiff neck

Another sign to watch for: Along with the start of your headache, your neck feels so stiff that it's difficult, even painful, to move. This could be a sign that something's brewing in the brain, spinal cord or the fluid surrounding it – meningitis being the big one, and this is worth a same-day medical exam, even if there's no other sign of infection, such as fever.

Deviation from your patterns

Don't get too focused on the pain level of your headache, cautions Peter Goadsby,a UCLA neurologist and president of the American Headache Society.

Instead of fixating on pain severity, think about whether any feature of your headache is out of the ordinary for you. Compare the headache with others you've had over the course of the last few days, weeks or months.

"People have a common misconception that if it feels really bad, you're going to die or something dreadful is always happening, and that's just wrong," Goadsby says. He notes common headache disorders – such as migraine, his specialty – can cause terrible pain but aren't necessarily suspicious.

It may be helpful to ask yourself, "Is this new for me?" If the answer is yes, it's important to follow up with your doctor.

New headache features could be a change in the timing of headache, pain in one area that never switches sides, a new or different aura beforehand or symptoms such as nausea or vomiting that you've never had before. And the same is true for headaches that get progressively worse over time, don't respond to medicines, or any type of headache that keeps coming back for someone who hasn't had trouble with them in the past.

Even so, just remember pain level can still signal an emergency if you get that thunderclap-style headache mentioned above, which Goadsby likens to "a baseball bat to the back of the head."

Trust your gut

For doctors, perhaps the most important factor when we're investigating a headache is nothing to do with the headache itself but instead the person experiencing it.

What seems like an innocent headache in a healthy person could be something critical for people with chronic illnesses such as HIV, cancer or even a history of cancer — if this is your situation, you should have a lower threshold to reach out to a doctor with any type of headache that's new. Likewise, it's OK to be more guarded about headaches if you're pregnant, over age 50, have disabilities or have suffered recent trauma such as a fall or concussion.

As with most things in the human body, it doesn't help to be too rigid when you're thinking about what's "serious enough" to worry about. When a headache gives you the feeling that something's not right, trust your gut — either get immediate, urgent care or write down all the details in a headache log, take it to your doctor and start asking questions.

Kristen Kendrick is a board-certified family physician in Washington, D.C., and a health and media fellow at NPR and Georgetown University School of Medicine.

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Kristen Kendrick