Do You Need an MRI to Diagnose Your Headache?

For the vast majority of headache evaluations, imaging of the brain will not be ordered. A healthcare provider can simply diagnose a headache disorder or a migraine based on a person's medical history, symptoms, and physical examination.

But in some instances, imaging of the brain (for example, an MRI of the brain or a CT scan of the brain) is needed to evaluate for serious, sometimes life-threatening, causes of a headache.

While not an exhaustive list, here are prime examples of when a healthcare provider would order imaging for your headache.

Worst Headache of Your Life (aka Thunderclap Headache)

The "worst headache of your life," or a thunderclap headache, is worrisome for a subarachnoid hemorrhage (a bleed in the brain) and requires an immediate CT scan.

If the CT scan of the brain is normal, and your healthcare provider is still worried about a subarachnoid hemorrhage, a lumbar puncture (spinal tap) will be performed.

A magnetic resonance angiography (MRA) and/or venography is also frequently done to further rule out any blood vessel problem in the brain.

A thunderclap headache can also be a sign of other serious conditions like a hypertensive emergency or an arterial dissection.

Sudden, Severe Headache on One Side of the Head

A sudden, one-sided onset of head pain, especially if the pain radiates into the neck, is worrisome for a carotid or vertebral artery dissection.

This is also a medical emergency and requires an emergent MRI of the brain and a CTA or MRA of the head and neck (these imaging tests look at the blood vessels in the brain).

Severe Headache in Pregnancy or Postpartum Period

While headaches are common in pregnancy, and most are not worrisome, a severe headache warrants imaging of the brain. For some serious medical conditions, like pituitary apoplexy or reversible cerebral vascular syndrome (when arteries in the brain spasm), pregnancy is a risk factor.

There are other serious medical conditions for a healthcare provider to consider when a woman has a severe headache in pregnancy, including stroke or cerebral venous thrombosis.

Headache in People With a Weakened Immune System

People with a history of HIV/AIDS or diabetes, people taking chemotherapy for cancer, or people taking long-term corticosteroids (like prednisone) have a weakened immune system, which means they may have difficulty fighting infections.

The major concerns about a headache in people with an impaired immune system include:

• A brain abscess
• Meningitis
• Cancer of the brain or spinal cord

A brain tumor and an infection in the brain (like an abscess) can be visualized with an MRI of the brain.

Headache in People Older Than 50 With Suspected Giant Cell Arteritis

Giant cell arteritis causes inflammation of certain large and medium-sized blood vessels, typically branches of the external carotid artery (a large artery in your neck).

This blood vessel inflammation may result in a variety of symptoms, but most notably a new headache (often the scalp can be tender to touch, but not always), jaw pain when eating, and sometimes vision changes. Some people also develop a fever and feel unwell with a loss of appetite and generalized body aches.

In addition to an erythrocyte sedimentation rate (ESR) or C-reactive protein blood test, a biopsy of the temporal artery and a high-resolution MRI are often ordered to confirm the diagnosis.

New Headache or Worsening Pattern

A headache that has a worsening pattern (that is, it's becoming more severe or frequent) warrants imaging of the brain in order to rule out bleeding in the brain (for example, a subdural hematoma) or a tumor.

A new headache—one that comes on suddenly and/or occurs in someone with a history of cancer or HIV—also warrants imaging. For the latter, there is a risk of cancer spreading to the brain or a brain infection.

Headache Plus Other Symptoms or Signs

Sometimes it's the symptoms associated with your headache that warrant neuroimaging—which could mean either a CT scan or an MRI, or both.

These associated symptoms or signs include:

• Neurological symptoms other than those found in a typical migraine aura (for example, weakness or numbness on one side of the body, blurry vision, or confusion)
• Neck stiffness, fever, or other whole-body symptoms like a rash
• A headache triggered by a cough, strenuous exercise, or sex
• A headache with a history of dizziness or balance problems
• A headache that occurs after a head trauma
• A finding of papilledema on physical exam (when the optic disc in your eye swells because of increased pressure in the brain)

A Word From Verywell

It is important to remember that, in most cases, brain imaging is not indicated for a headache or migraine diagnosis. Most headaches are simply that—just a headache, a benign medical problem.

That being said, it is important to see a healthcare provider for your headache evaluation. It can be challenging distinguishing what is serious and what is not—and sometimes it's the small medical nuances a healthcare provider picks up that clinch the diagnosis.