“I thought it was just my sinuses that hurt,” Billie says. “But it didn’t get any better, and it was different from the headaches I usually got. My face hurt so much I didn’t even want to brush my teeth. So my husband called the doctor, and he told us to come in right away. Turns out I had giant cell arteritis [inflammation of the arteries in the face]. If I had waited, the doctor said I might have had a stroke.” Billie’s story serves as a warning that sometimes a headache is more than just a headache. In fact, a headache can be an early warning sign of more complicated and serious health issues such as stroke, infection, or high blood pressure. RELATED: When Should You Worry About Your Headache and Seek Immediate Help? Risk factors for stroke at a younger age include:

Inherited or acquired conditions that cause abnormal blood clotting such as sickle cell anemiaSmokingUse of birth control containing estrogenPregnancyHigh blood pressure during pregnancyMigraine with aura

In addition, half of those who die each year from a ruptured brain aneurysm — which typically causes a severe and sudden headache —are under age 50, according to the Brain Aneurysm Foundation. RELATED: What You Need to Know About Migraine and Stroke

Primary Versus Secondary Headaches

When you see a doctor about a headache, they gather information about your symptoms to determine if your headaches are primary or secondary. A primary headache is its own condition, such as migraine, tension headache, or cluster headache. When the headache is caused by another underlying disorder (as in Billie’s case), it’s called a secondary headache. Although primary headaches like migraine can be debilitating, they aren’t life-threatening, says Roderick Spears, MD, a neurologist and headache specialist at Penn Medicine in Philadelphia. On the other hand, a secondary headache can be the sign of a serious health issue, maybe even one that requires urgent medical attention. Primary headaches are much more common than secondary headaches; more than 90 percent of the people who seek treatment for their headaches are diagnosed with a primary headache disorder, according to a review published in January 2018 in The American Journal of Medicine. A new headache that lasts all day and night, every day, is concerning and should be investigated as a secondary headache, according to the American Headache Society (AHS).

The SNOOP4 Tool Identifies Headache Red Flags

The mnemonic “SNOOP4” helps doctors determine when further investigation — possibly including imaging tests such as magnetic resonance imaging (MRI), lumbar puncture to examine spinal fluid, or blood tests — are needed to diagnose the cause of a person’s headache.

Systemic Symptoms

Systemic symptoms are those you feel in other parts of your body, besides your head. This could be a fever, loss of appetite, or weight loss. Conditions that may cause such symptoms include meningitis, vasculitis (inflammation of the blood vessels), cancer, and infection. The “S” in SNOOP4 can also stand for “secondary risk factors,” so if you have a headache in addition to HIV or cancer, see your doctor about it.

Neurologic Symptoms

Neurologic symptoms include confusion, blurry vision, personality changes, weakness on one side of the body, numbness, or sharp facial pain and could indicate a tumor or a stroke.

Onset Sudden or Abrupt

This means that the headache happens suddenly, with no warning. Sometimes these are called “thunderclap” headaches. This can occur when headaches are caused by bleeding in the brain. RELATED: How the World’s Hottest Pepper Landed a Man in the Hospital

Older Age

If you are older than 50 and experience a new or progressive headache, it may be giant cell arteritis or a brain tumor.

Pattern Change or Progression

A new headache is cause for concern if it is significantly different from your typical headaches, if your headaches are happening more often, or if it is the worst headache you have ever had.

Precipitated by Valsalva Maneuver

The Valsalva maneuver is a breathing technique that your doctor may use to rule out what’s called a posterior fossa lesion or tumor. The posterior fossa is the small space in the skull near the brain stem and cerebellum. Other symptoms of this type of tumor are drowsiness, imbalance, nausea, and vomiting, according to MedlinePlus. To perform the Valsalva maneuver, breathe out strongly through your mouth, pinch your nose shut and press the air out like you are blowing up a balloon.

Positional Aggravation

If your headache comes on from sitting or standing, it may be related to high or low spinal fluid pressure. High pressure headache, also known as idiopathic intracranial hypertension (IIH), is caused by elevated pressure inside the skull due to too much cerebrospinal fluid, according to the American Migraine Foundation. Spontaneous intracranial hypotension (SIH) is a low pressure headache, and it’s the result of low spinal fluid pressure in the brain caused by a leak of spinal fluid, according to the American Migraine Foundation.

Papilledema

Papilledema occurs when increased pressure in or around the brain causes the part of the optic nerve inside the eye to swell; this is considered a medical emergency, according to the American Academy of Ophthalmology. The presence of papilledema may confirm a diagnosis of idiopathic intracranial hypertension.

Headache Caused by High Blood Pressure

Extremely high blood pressure can cause a headache (and sometimes nosebleed) in people with or without diagnosed hypertension. This type of headache only happens when blood pressure is severely elevated to 180/120 millimeters of mercury (mm Hg) or higher, according to the American Heart Association. Normal blood pressure is 120/80 mm Hg. When blood pressure is extremely elevated, it’s a medical emergency known as a hypertensive crisis, and medical attention is needed right away.

Signs of a Stroke

When the circulation of blood and oxygen to the brain is interrupted for any reasons, a stroke occurs. According to the National Institute of Neurological Disorders and Stroke, one sign of stroke is a sudden severe headache with no obvious cause. Other symptoms are:

Sudden weakness or numbness, especially on one side of the bodySudden confusionSudden trouble speaking or understanding speechSudden difficulty seeing from one or both eyesSudden dizziness, loss of balance, or difficulty walking

The National Stroke Association suggests remembering “FAST” — a quick test to determine if someone should seek help for a stroke.

Face Does your face droop when you smile?Arm Does one arm drift downward if you try to raise both arms?Speech Does your speech sound slurred?Time If you or someone else has these signs, call 911.

When an ischemic stroke (a stroke caused by a blockage in a blood vessel) occurs as a complication of migraine with aura, it’s called a migrainous stroke or migrainous infarction. Like any stroke, a migrainous infarction is considered a medical emergency. Migrainous stroke is very rare and accounts for less than 1 percent of strokes, according to the Cedars-Sinai Health System.

Signs of a Cluster Headache

While a cluster headache is a type of primary headache and not a sign of another underlying condition, the severe pain these headaches cause can lead some people to contemplate suicide. Cluster headaches occur suddenly and cause a piercing and very intense pain, almost always on one side of the head. A runny nose and tearing on the side with the pain is also common. Cluster headaches generally last between 15 minutes and three hours, without treatment. Cluster headaches get their name because they come in clusters. A person might have daily cluster headaches for a month or more, for example, and then none for a year. Treatment for cluster headaches can be high-flow oxygen through a mask; nerve blocks, in which a numbing agent, or anesthetic, is injected into the scalp near particular nerves; or daily doses of the drug verapamil.

Seek Help for Serious, Sudden Headaches

Although most headaches are not serious and will go away on their own, it’s important to recognize when headache pain could be a sign of a larger issue. Stephen D. Silberstein, MD, director of the Jefferson Headache Center at Thomas Jefferson University in Philadelphia and past president of the American Headache Society, advises: “If your headache is bad, new, or changing, see somebody.” Additional reporting by Becky Upham.