Why You Need an MRI: Evaluating Secondary Causes

If your headache has vanished after taking indomethacin, it can feel like the mystery is solved. However, in the world of Hemicrania Continua (HC), a successful “indomethacin trial” is only one part of the puzzle. Even when the medication works perfectly, a Brain MRI is generally recommended as a critical step in your care ^[1][2].

Why Response Isn’t Proof

It is a common misconception that if a headache responds to a specific drug, it must be a “primary” headache (like a migraine or HC). In reality, several serious “secondary” conditions—where the headache is a symptom of another underlying issue—can mimic HC perfectly and even disappear entirely when you take indomethacin ^[2][3].

Because an indomethacin response does not “prove” the headache is primary, imaging is used to ensure that the pain isn’t being caused by a structural or vascular problem ^[1][4].

What the MRI Looks For

A standard brain MRI might not always capture the specific areas that can mimic HC. To ensure your evaluation is thorough, your doctor will use your specific history and clinical examination to decide which specialist-directed imaging protocols (like contrast, sellar sequences, or vascular studies) are needed ^[2][3].

The Pituitary Gland and Sellar Region

The pituitary gland is a small, pea-sized organ at the base of the brain in the “sellar” region. Pituitary masses, such as pituitary microadenomas, are sometimes found in patients presenting with HC-like headaches ^[1][5]. While microadenomas are actually very common incidental findings in the general population and usually do not produce nerve compression, larger lesions can cause mass effect and lead to side-locked pain ^[5]. Because these can sometimes mimic HC symptoms that respond to indomethacin, doctors may request dedicated pituitary views (also called sellar views) ^[2][6]. Your care team will interpret whether any small finding is actually causal or just an incidental finding.

Vascular Structures

Several blood vessel issues can produce HC-like symptoms. These include:

• Internal Carotid Aneurysm: A bulge in a major artery in the neck or head ^[1].
• Cervical Artery Dissection: A tear in the wall of an artery in the neck, which can be life-threatening if not identified ^[4].
• Carotid-Cavernous Fistula: An abnormal connection between an artery and a vein behind the eye ^[7].

Your doctor will decide if a specialized vascular scan (like an MRA or CTA) is indicated based on your exam. A routine brain MRI alone will not always adequately assess every aneurysm or dissection.

Inflammatory and Other Rare Causes

In some cases, inflammation of the brain’s lining (pachymeningitis - often noted as “dural enhancement” on a scan) or the area behind the eye (Tolosa-Hunt syndrome) can present exactly like HC ^[8][9]. Very rarely, a tumor in the neck or upper spine can also trigger these symptoms, which is why doctors may order additional imaging if the brain MRI is clear but symptoms persist ^[10][11].

Questions to Ask Your Care Team

Instead of auditing your radiology report for specific medical jargon (since omission of a term doesn’t necessarily mean the radiologist missed evaluating that area), you can ask your neurologist these questions to understand your imaging plan:

• “Was this scan the appropriate protocol (e.g., with contrast) to rule out secondary mimics for my specific symptoms?”
• “Did the imaging check the pituitary area and cavernous sinus?”
• “Based on my exam, do we need to do vascular imaging (like an MRA or CTA of the neck/head) to check the arteries?”

Next Steps

If your MRI is clear, it significantly lowers concern for secondary causes, even though it doesn’t offer a 100% guarantee. At that point, you and your doctor can focus on long-term management and finding the lowest effective dose of medication to keep you pain-free. If a secondary cause is found, the treatment will shift to addressing that specific issue, and the outcome will depend heavily on the cause itself ^[7]. Regardless of the result, this scan is an essential bridge between a suspected diagnosis and a safe long-term treatment plan.