A computed tomography (CT) scan uses a series of X-rays to create detailed, cross-sectional pictures of the body’s internal structures. A migraine is a primary neurological disorder characterized by moderate to severe head pain. The core answer to whether a CT scan can detect a migraine is no, as the scan captures static, physical brain structures. Doctors use this imaging tool to rule out structural problems, not to diagnose this complex, functional condition.
The Role of CT Scans in Headache Evaluation
The primary application of a CT scan is to rule out serious, life-threatening causes of pain, identifying “secondary headaches.” The scan quickly identifies issues like acute intracranial hemorrhage, large tumors, hydrocephalus (buildup of cerebrospinal fluid), or structural abnormalities of the skull.
A physician orders an urgent CT scan if a patient presents with specific “red flag” warning signs. These include the sudden onset of a severe “thunderclap” headache, or a new headache in a patient over the age of 50. Imaging is also necessary for those who are immunocompromised or have a history of cancer.
Other concerning symptoms prompting immediate imaging include neurological deficits, such as altered mental status or papilledema (swelling of the optic nerve). A headache that progressively worsens in frequency and severity also indicates the need for a CT scan.
Why Structural Imaging Cannot Detect Migraines
Migraines are a primary headache disorder, meaning the pain is the condition itself, not a symptom of a structural illness. The pathophysiology involves complex neurochemical changes and abnormal electrical activity within the brain. These changes are “functional” because they relate to how the brain works, not to its physical form.
A CT scan is a structural imaging tool designed to visualize the brain’s anatomy. It provides a high-resolution picture of bone, fluid, and soft tissue, making it excellent for detecting macroscopic physical damage. Since a typical migraine attack does not cause visible structural damage, the scan results are almost always reported as normal. The microscopic events characterizing a migraine are invisible on a standard CT scan, meaning this imaging is inappropriate for routine diagnosis.
Clinical Criteria for Migraine Diagnosis
Since structural imaging is ineffective, a migraine is diagnosed clinically, relying heavily on the patient’s detailed symptom history. The gold standard is the criteria established by the International Headache Society (ICHD-3). This framework requires a patient to have experienced at least five attacks that meet specific criteria.
Required Attack Characteristics
Each attack must last between four and 72 hours if untreated. The headache must possess at least two of the following four characteristics:
- Unilateral location
- Pulsating quality to the pain
- Moderate or severe pain intensity
- Aggravation by routine physical activity
The attack must also be accompanied by at least one of two associated symptom groups: nausea and/or vomiting, or a combination of photophobia (increased sensitivity to light) and phonophobia (increased sensitivity to sound). A comprehensive review of these symptoms allows a physician to accurately classify the headache as a migraine.