Headaches are a common experience. While most are benign, some may signal an underlying health condition. Medical imaging, particularly magnetic resonance imaging (MRI), helps determine if a headache has a structural cause. An MRI does not directly visualize pain; instead, it provides detailed images of the brain’s anatomy to identify potential abnormalities that could be generating the headache.
Understanding MRI Scans
Magnetic Resonance Imaging (MRI) is a non-invasive medical imaging technique that generates detailed pictures of internal body structures without using X-rays. It uses a powerful magnetic field to align hydrogen atoms within tissues. Radio waves are pulsed, briefly knocking these atoms out of position. When turned off, the atoms return to alignment, releasing energy signals detected by the scanner.
A computer processes these signals to create cross-sectional or three-dimensional images. For headaches, a brain MRI provides clear views of the brain, blood vessels, cranial nerves, and surrounding soft tissues. It is particularly useful for examining brain and nervous system structures.
When Headaches Prompt an MRI
An MRI is not typically performed for routine headaches, as most are not caused by serious underlying conditions. However, specific “red flag” symptoms can prompt an MRI to investigate a potential structural cause. These include a sudden, unusually severe headache, often described as the “worst headache of your life.” Headaches that are new or change in pattern, especially in individuals over 50, also warrant imaging.
An MRI may also be recommended if headaches are accompanied by neurological symptoms, such as vision changes, weakness on one side of the body, confusion, or difficulty speaking. Headaches that worsen over time, occur daily, or persist after a head injury are additional reasons. New headaches in individuals with a history of cancer or those who are immunocompromised often necessitate an MRI.
Headache-Causing Conditions Visible on MRI
An MRI can reveal various structural abnormalities or diseases in the brain that may cause headaches. Brain tumors, appearing as distinct masses, are detectable and can lead to headaches due to pressure or inflammation. Aneurysms, weakened, bulging areas in blood vessel walls, and other vascular malformations can also be identified. These conditions might cause headaches, particularly if they rupture or leak blood.
Hydrocephalus, an abnormal buildup of cerebrospinal fluid in the brain’s ventricles, appears as enlarged fluid-filled spaces. This excess fluid increases pressure within the skull, contributing to headache symptoms. Chiari malformation, a structural defect where cerebellar tonsils extend into the spinal canal, is clearly visible. This malformation often causes headaches worsened by coughing or straining due to obstructed cerebrospinal fluid flow.
Infections like encephalitis (brain inflammation) or brain abscesses can show up as altered signal intensity, edema, or enhancement, indicating inflammation or pus collection. Signs of a stroke or hemorrhage, such as tissue damage or bleeding, are also identifiable. Traumatic brain injuries, including contusions or bleeding, can be assessed through MRI scans.
What MRI Scans Don’t Show About Headaches
While highly effective at revealing structural issues, MRI scans have limitations in diagnosing all headache types. Common primary headache disorders, such as migraines, tension-type headaches, and cluster headaches, typically do not present with identifiable structural abnormalities on a standard MRI scan. A normal MRI result for these conditions means the headache is not caused by a visible problem like a tumor or aneurysm. The absence of structural findings does not diminish the reality or severity of the patient’s pain.
However, advanced MRI sequences have indicated subtle changes in the brain for individuals with migraine or chronic tension-type headaches. These can include white matter hyperintensities, small bright spots on certain MRI images, or minor volumetric changes in specific brain regions. The clinical significance of these subtle findings is still being researched, and they are not typically considered the direct cause of the headache pain itself. Therefore, a “normal” MRI for primary headache disorders confirms the absence of a structural cause and guides further management toward symptomatic treatment.