An “Acute Headache” is one that began recently, less than 3-4 weeks ago, maybe just a few days ago, or even today. Since it’s highly likely to get better & go away on its own, our job as clinicians isn’t so much to treat, but to diagnose — ruling out those unusual conditions that can kill, before it’s too late. So we mull over all the possibilities (see “Acute Headache” for the clinician’s condensed thought-process when face-to-face with a patient).
We always want to be sure they don’t have other symptoms of Covid-19. But we can’t just send them off for a test if they may have diseases in the first column below. Every site has its own way of addressing this. The rest of this discussion assumes we’ve ruled it out. See also Covid-19.
Causes of Acute Headache
|zz zzDo Not Miss (rare)||zzzzMore Common Conditions|
|** Subarachnoid Hemorrhage|
** Increased Intracranial Pressure (in brain)
** Meningitis (and other brain infections)
** AIDS-Related Illness
** Carbon Monoxide Poisoning
** Temporal Arteritis
** Epidural Hematoma
** Anemia (if acute or severe)
** Hypertension (severe)
** Acute Closed-Angle Glaucoma
** Depressed and Suicidal
|** Allergic Rhinitis (hay fever)|
** Influenza (& other illnesses with fever)
** Neck Sprain or Strain
** Medications / Drugs / Toxins / Irritants
** Head Trauma (minor)
** “Normal” Headache
** Stress, Anxiety, Depression
First Episode of “Recurrent Headache“
Beginning of “Chronic Headache”
The conditions in our “Do Not Miss” column are uncommon. They can usually be easily & rapidly ruled out, as long as we think about them. The rest, in the “More Common” column, are harder to diagnose with certainty. We make educated guesses, but if we’re wrong, they’ll get better on their own anyway.
We’ll start with the rare-but-potential-lethal conditions in the “DO NOT MISS” column. Scroll on down for Common (non-serious) Causes of Acute Headache.
Potentially Lethal / Catastrophic Causes of Acute Headache
** Subarachnoid Hemorrhage (SAH) — Let’s begin with a true case:
A 44-year-old woman, volunteer at my colleague’s free clinic, mentioned her bad headache requiring lots of ibuprofen. My colleague urged she see her regular doctor, who prescribed an antibiotic for sinusitis. A week later, symptoms unimproved, they changed the antibiotic. The headache persisted another week, they performed a CT Scan of the brain, and Spinal Tap; both were normal. The fourth week, her cerebral aneurysm ruptured completely, and the lady died.
What went wrong?
An aneurysm is a weakened artery (anywhere in the body), that weakens as it balloons out over time. When one in the brain ruptures and bleeds, causing a Subarachnoid Hemorrhage (SAH), over half of patients succumb then-and-there. But up to 50% just get a small “warning leak” which seals over. That’s unstable, will fully burst in a few weeks (rarely, just 1-2 days), but offers a window period for life-saving surgery.
A CT Scan finds virtually 100% of leaked aneurysms within the first 12 hours, over 90% within the first 24 hours. But this “sensitivity” (i.e. no false-negative scans), decreases to 60% by the first week, as blood gets resorbed. Similarly, a Spinal Tap is highly sensitive throughout the first week, but much less so after two. The test that’s virtually 100% for sure, always obtained before surgery, is an arteriogram (a.k.a. angiogram), but it’s invasive, with a 1 in 1,000 risk of causing stroke.
So if a clinician considers the diagnosis of SAH at all, don’t delay. However, we obviously don’t order CT’s and spinal taps on everyone with a headache. Who should get them? Anyone with three clinical features:
- New onset of the “worst headache ever” (“worst” defined by prior headaches and pains)
- Sudden Onset: Pain usually reaches its greatest intensity immediately. Makes sense — a drop of blood spurts out, symptoms begin then & there. The medical term is “thunderclap” — Pow! Pain that builds up any slower is much less concerning.
- The pain is constantly present, doesn’t disappear for a few hours and recur.
Of course, any headache is the “worst ever” for someone who’s never had one before. But “thunderclap” onset is very uncommon. I encounter such patients around once every 5 years (the tests have usually been normal).
If the sudden onset of headache occurred during a strain, it should raise suspicion. This includes coughing, lifting, sex, etc. Sadly, some pregnant women die of SAH while pushing during labor. People with Polycystic Kidney Disease (rare) are at high risk of brain aneurysms. A family history of SAH (often reported as a “stroke,” but at an age younger than typical strokes) may suggest unusual genetic conditions (especially if more than 1 in the family).
Certainly, anybody with a new headache deserves a thorough neurologic exam, but in most patients with a “warning leak,” it’s normal. The common clinical error is to assume that patients with SAH look ill — true for the fully ruptured aneurysm or large leak, but not a small one.
MORAL: a patient with the very sudden onset of the “worst headache ever” that’s constantly present, even if not appearing in much pain, needs a CT Scan & Spinal Tap, most easily obtained in an ER. If 2 weeks have already gone by, the clinician should consult a neurologist or neurosurgeon about need for an angiogram.
** Increased Intracranial Pressure (↑ ICP) — Pressure in the brain! If not found & treated (usually surgically), pressure can force the brain down from the skull and pith it on the spine (you have to be willing to hear about some unsightly occurrences if you want to read this Website). Causes of ↑ ICP include:
- Tumors (malignant or benign)
- Blood clots (hematomas)
- Hydrocephalus (excess cerebrospinal fluid build-up)
All are easily identified by a “Head CT Scan“. But again, we don’t order them on everyone with headache (or we’d cause a couple of cancers in the long run; see Radiation Risks of X-Rays). We’re most concerned if a patient has:
- Daily headache that’s getting worse week by week
- Daily nausea / vomiting
- New personality changes; certainly if there’s new confusion
“Daily” is a key; obviously none of these conditions hurt one day but not the next. Since they may grow slowly, we’re less concerned if the pain has been the same ever since onset. We worry a little more about brain tumors if the pain gets worse with straining. And of course we obtain a CT Scan if there are any abnormalities on neurologic examination, which usually go along with any new symptoms, including:
- double vision
- loss of part of a visual field, like you can’t see anything on the side of an eye while focusing straight
- slurred speech; other speech problems
- loss of balance or coordination
- weakness of arms and/or legs
- incontinence (can’t hold urine at all)
We’re often more liberal in obtaining Head CTs in certain cases:
- Head trauma (within the last few months)
- Anticoagulant use: warfarin (Coumadin®) & newer “blood thinners,” not so much aspirin
By the way, CT scans aren’t as good as MRIs for finding brain tumors in general, but they’ll find those large enough to cause a headache.
** Meningitis & Encephalitis — Bacterial meningitis, the notorious killer, isn’t subtle. There’s usually a fever, headache is severe, and the patient cannot bend their neck forward. If someone can bend their neck to look down at their belly button, I’m not worried. Viral meningitis is less severe, but also less dangerous. Suspected bacterial meningitis goes straight to ER by ambulance, with a shot of antibiotics first if a long delay is anticipated.
In Encephalitis, a more diffuse infection of brain tissue, confusion is more dramatic than the headache. Patients may not remember the year, maybe can’t do simple math like count backwards by 3’s (or even 1’s), or even make sense. We call 911 for them as well.
Some other terrible, imminently fatal, illnesses can begin with fever & headache. But then it’s the fever that orients our diagnostic thought process. See our topic Fever.
** AIDS-Related Illnesses — Several brain infections afflict persons with AIDS. People with HIV usually know if their immune system is at risk (if they’ve been on successful treatment, it’s not). But lots of infected persons don’t even know they have HIV!
If a patient with new headache hasn’t had an HIV test in several years or more, but has had past risks for HIV (like unprotected sex with many partners, or sharing needles), clinicians should look for suggestions of undiagnosed infection that could be advanced. These include:
- White patches in the mouth (thrush)
- White vertical corrugated streaks on sides of tongue (hairy leukoplakia)
- Unusual swollen glands (lymph nodes): back sides of neck, armpits, inside of elbow
- Purple bruises on skin or in mouth (Kaposi’s Sarcoma)
- Unusual rashes, especially on the face
If we think AIDS is a possibility in terms of the Headache, we do a rapid HIV test. If positive, we send them to an ER, since the test to evaluate their immune system won’t be back for 1-2 days.
** Carbon Monoxide (CO) Poisoning — A student once described how she sought ER care for a new headache, and was reassured it was just “tension.” She returned several hours later feeling even worse, they told her, “go home and relax, honey.” Home happened to be where the faulty heater leaked; fortunately an astute physician assistant made the connection on her third visit, or I might never have heard the story.
Whenever a new headache occurs in winter, or during a car ride, consider possible CO Poisoning. Other symptoms may merely be an inability to concentrate. Textbooks mention “cherry-red skin changes”: that’s rare, & end-stage (just before death). If two patients from the same environment ever develop simultaneous symptoms, CO poisoning is tops on our list. Easy diagnosis, once we consider it, by testing arterial blood gases in an ER.
** Temporal Arteritis –– Inflammation of the temporal artery, which curls around the side of the forehead (& has a pulse). It brings blood circulation to the eye, so Temporal Arteritis can cause sudden [& permanent] blindness.
It’s an easy diagnosis if we think of it, because it never [hate to say “never”] occurs under 50-years-old; most patients are over 70. Half of patients have “jaw claudication;” jaws ache with eating or speaking (which also means half don’t). Other symptoms may include fatigue, weak arms, temporary visual loss, or fever (which may confuse the diagnosis). But the key is always: new headache in a person >50.
A simple, cheap non-specific blood test for any kind of inflammation is always [hate to say “always”] elevated: the Erythrocyte Sedimentation Rate (ESR; Sed Rate). Normal = ½ your age, + 5 in women; in Temporal Arteritis it’s invariably over 50, usually around 100. There’s usually a mild anemia of chronic disease. Everyone >50-years-old with a new headache needs an ESR test.
The treatment is steroids for 2 years. Not anabolic home-run-hitting steroids, but corticosteroids, which have lots of long-term side effects. But that’s still better than permanent blindness. If the ESR is high, we begin treatment & schedule a biopsy for complete proof. The biopsy is best done within 2 weeks, or the steroids may interfere with results. Regular surgeons, plastic surgeons, and ophthalmologists can all do the biopsy; one might have scheduling availability before another.
** Epidural Hematoma — Tony Award-winning actor Natasha Richardson fell on a beginners’ ski slope in rural Quebec, hitting her head. She got up and laughed, refused to seek care because she felt fine. Two hours later a headache developed; four more hours passed before reaching a full-fledged hospital, at which point she may have already been brain-dead. Sadly, she died.
An Epidural Hematoma occurs from blunt trauma that ruptures an artery between the brain lining (dura) and the skull. There may or may not be brief loss of consciousness or a skull fracture. Patients experience a “lucid interval” between injury and onset of headache, during which they feel fine. We worry about any patient who develops a headache within 24 hours (rarely 48 hours) of head trauma, which gets progressively worse (we don’t worry if it’s only the swollen bump of scalp skin that hurts).
The elderly are more at risk. If we have any doubt, we send the patient to an ER for an immediate Head CT scan, which is 100% accurate. Timely surgery is almost always successful.
** Acute Anemia — Anemia (inadequate amount of red blood cells) by itself usually has no symptoms. But if enough blood is lost quickly, or if the red blood cell count eventually drops low enough, people may complain of “headache.” A simple blood test for a Complete Blood Count (CBC) makes the diagnosis.
The most common symptom of anemia is shortness of breath during exertion. If this is absent, there’s enough probably not serious enough anemia to cause a headache. Gastrointestinal bleeding can come out simply as black, tarry stools (called “melena”). However, iron tablets & Pepto-Bismol® [or its generics: “pink liquid”] can also turn stools black, without any consequence.
Mild anemia, or long-standing anemia, won’t cause headaches.
** Hypertension — High Blood Pressure almost never causes a headache! It would have to reach around 240/120, maybe only 180/110 if also associated with vomiting. The danger of us mentioning blood pressure & headache together is that people who feel fine think their pressure is OK & skip their medicines.
I tell my patients that in both English & Spanish, the problem is linguistic (maybe lots of other languages too). High Blood Pressure (Hypertension) is asymptomatic; we treat to prevent strokes & heart attacks, not to make you feel better. “Nervous pressure” and “tension” are very symptomatic, make you feel horrible, but don’t kill.
** Acute Closed-Angle (a.k.a. “narrow-angle”) Glaucoma — This hits otherwise-well people suddenly, causes extreme eye pain or headache behind the eye, with vomiting & blurry vision. It’s not so common, but requires emergency surgery within 24-48 hours to save the eye. There’s nothing subtle about it, except that clinicians might forget to consider the eye when a patient has headache & vomiting.
The much more common type of Glaucoma is chronic, open-angle (a.k.a. “wide-angle”). It has no symptoms at all, is usually detected by measuring eye pressures, causes blindness in the long run, & can be controlled with medications. It’s a completely different condition from the acute version that causes a headache.
** Depression AND Suicidal — Depressed people might have frequent headaches. They also might prefer to discuss a physical ailment rather than their psychological distress. Clinicians are usually able to sort this out; then it’s essential to determine if they’re actively suicidal. The best way is to ask, simply and matter-of-factly, “Have you been so depressed that you’ve thought of killing yourself?”.
If the person replies, “yes,” we determine how seriously they’re thinking about it. If they have a concrete plan in mind, and a means to do it, we call the police to take them to a psychiatric ER. About 40% of people who kill themselves see a health care provider the week before, though not for depression. It’s their subconscious “cry for help,” without explaining. Maybe they seek care for a cold, or just a check-up; maybe a “headache.”
We never worry about “planting the idea,” because that’s impossible. Nobody would ever say, “Oh, I never thought about that; maybe I should.” Quite the contrary, anyone who is the least bit suicidal can’t escape the torment. They’re usually relieved we’ve asked.
That’s it for “Not to Miss” causes of Acute Headache. Hopefully you never have one. Now on to the much MORE COMMON CONDITIONS in our table, bothersome but not serious.
Common Causes of Acute Headache (not Serious)
** Allergic Rhinitis (Hay Fever) / Sinusitis / Common Cold — If there are significant nasal symptoms like congestion, runny nose, sneezing, or facial pressure, & the headache is mostly felt in the front of the head, one of the above is likely the cause. See our topic Nasal Congestion for ways to distinguish among these conditions. But at any rate, if nasal symptoms are present, we’ve identified the likely cause of headache.
** Influenza (& other fevers) — Any disease that causes a fever can cause a headache. As long as they don’t look horribly ill with stiff neck (meningitis), or act confused (encephalitis), we forget our differential diagnosis of “headache” & think through the causes of “fever.” See our topic Fever for a broader discussion. As noted before, first rule out Covid for any patient with fever and headache.
** Neck Strain or Sprain — Any trauma to the neck can cause a headache. Sometimes it’s obvious, like getting rear-ended in a car. But the event may be trivial, like a sudden twist, or having to keep the neck in an unnatural position for a time. In such cases, the pain may begin a day or two later (when muscles swell inside), such that the person doesn’t recall what happened.
We suspect the neck as the source of “headache” if pain is increased by bending or rotating it. We also palpate the muscles & bones for tenderness, & have the patient move their neck in different directions against resistance (we push against it). If any of that hurts, we have our diagnosis.
** Medications, Drugs, Toxins, Irritants — Almost any medicine might be able to cause a headache. We diagnose this if there’s no other cause for a patient’s headache, and they had recently begun taking something new. Then we’d look it up in our resources for medication side effects, and see if the medication had ever been reported to be associated with a headache (but we’re careful with our conclusions; please see Beware Reading About Medication Side Effects).
The same goes for herbs, supplements, and street drugs. In terms of the latter, not only might the drug cause headache, but withdrawing from it might also. Same holds true for medicines & any substance.
If a person gets a headache repeatedly in a certain environment, we’d suspect an environmental cause. These can range from life-threatening (like Carbon Monoxide), to simply annoying (like ammonia). Diagnosis takes detective work.
** Minor Head Trauma — It goes without saying that head trauma can cause an “Acute Headache,” due not to brain injury, but rather skin swelling. The pain is felt mostly at the point of injury, and is not getting worse or spreading all over. The patient acts normally, and is not confused. Unfortunately, this can be hard to determine if they’re what we call “altered” (drunk or high).
Sometimes there’s an obvious lump that’s tender, but sometimes the swelling is stuck between the skull and a naturally-tight scalp. The latter hurts more, especially when pressed on. This type of injury is never dangerous, as long as the headache doesn’t get continually worse, or spread all over. Even a fractured skull isn’t dangerous unless there’s a deep wound over it, or if it’s so broken that bone presses downward (there’s no treatment for most fractured skulls; the skull doesn’t need a cast, which would be tough to do anyway).
What matters is brain injury, which we determine by how a person is thinking & behaving, not by their headache. This can be hard to tell if the person is drunk or high. See a brief discussion of Concussion and Post-Concussive Syndrome. Also see Epidural Hematoma for the person who has minor head injury, then starts to get worse later (within 24 hours, rarely 48).
Perhaps the most dangerous and overlooked aspect of acute head trauma is a broken neck, which can paralyze. Picture a person hit on the forehead, blood streaming down their face, everybody screaming. Nobody besides a young infant can lose too much blood from the head or face. The most important component of first aid is to immobilize the neck (may require calming the person). If you can push gently, then more forcibly, on each of 7 vertebrae (neck bones), & there isn’t one in particular that hurts a lot more than the others, there’s no broken neck. This only works if the person isn’t confused or drunk / high, isn’t elderly / fragile, and doesn’t have major injury elsewhere (a broken leg can distract from the pain of a fractured vertebra, though the latter is what kills). If in doubt, call an ambulance.
** “Normal” Headache — This is my own coined term; it’s natural to get a headache in certain circumstances. Mild dehydration, hunger, cold, lack of sleep… anything that upsets the body can be responsible. If you break your toe & hobble around, your head will hurt. Uncomfortable from constipation? You get the idea.
Anything that gets on our nerves, interferes with concentration, can cause a headache. Too much concentration can also cause a headache. Usually the cause is obvious, but people don’t realize it.
** Stress / Anxiety / Depression — Stress certainly generates discomfort, so as the Physiologic Headache above, it’s notorious for causing a headache. Everyone knows that excessive concentration causes headache, like studying for exams; one possibility is that the muscles of our face, head, & neck tighten too long without relaxing. Someone dealing with stress is preoccupied 24/7, at least while they’re awake.
Anxiety and Depression are not exactly “Stress.” They’re illnesses in which one is not able to cope with life events, or life in general, the way most of us can. They are also well-known causes of “Headache”.
All a medical provider can do for stress is to reassure the patient that their headache is “normal” in a sense. It’s not a tumor, hemorrhage, or stroke. Not an ideal consolation, but it usually helps in some sense. People with clinical Anxiety or Depression can benefit from a variety of treatments, both medication and psychological.
** First Episode of “Recurrent Headache” — It’s impossible to diagnose a Migraine during the first episode. We may have a decent suspicion, may even suggest the possibility. But since the word carries a lifetime label of illness, it’d be unfair to apply it loosely. Headache researchers don’t say “Migraine” until the 5th episode; “Tension Headache” requires nine. See topic Recurrent Headache.
** Beginning of “Chronic Headache” — Chronic headaches are those lasting over a month, maybe years. But they all have their beginning, which can be hard to identify at first. See topic Chronic Headache.
See also Acute Headache for the clinician’s condensed thought-process when face-to-face with a patient.