How Is Relapsing-Remitting MS Distinguished From Migraine?

Finding out you have “spots” or white-matter lesions on your MRI can be alarming, but these spots are not unique to multiple sclerosis (MS). Doctors distinguish relapsing-remitting MS from other conditions by carefully analyzing the specific location, shape, orientation, and features of the lesions, and most importantly, by ensuring these imaging findings match your actual physical symptoms. MS is never diagnosed just by counting spots on a scan ^[1]. Instead, neurologists use a framework called the McDonald criteria to confirm that damage has occurred in different parts of the nervous system (dissemination in space) and at different times (dissemination in time), while systematically ruling out mimics like migraine, age-related changes, or other inflammatory disorders ^[2].

Note: Sudden-onset weakness, numbness, speech difficulty, severe imbalance, or vision loss warrants urgent medical assessment, as stroke and other emergencies can mimic demyelinating symptoms.

The Anatomy of an MS Lesion

To determine if a lesion is likely caused by MS, neuroradiologists look for specific characteristics:

• Shape and Orientation: MS lesions are often ovoid (egg-shaped). Classic MS lesions, known as Dawson’s fingers, radiate outward from the brain’s fluid-filled spaces (ventricles) at perpendicular angles ^{[3] [4]}.
• Specific Locations: While many conditions cause spots deep in the brain, MS characteristically affects specific areas. These include the periventricular area (around the ventricles), the juxtacortical/cortical region (the U-fibers right beneath the brain’s surface and the cortex itself), the corpus callosum (the bridge between the two brain hemispheres), the infratentorial region (brainstem and cerebellum), the spinal cord, and the optic nerve ^{[3] [2]}.
• Enhancement and Activity: By using a contrast dye called gadolinium, doctors can look for recent inflammation. Gadolinium enhancement indicates a temporary disruption in the blood-brain barrier, which usually reflects relatively recent inflammatory activity ^{[1] [5]}. Seeing both enhancing and non-enhancing lesions on a single scan can provide evidence of dissemination in time. However, a non-enhancing lesion is not necessarily “healed” or old, as scan timing and treatments like steroids can affect enhancement ^[6].

Differentiating MS from Common Mimics

Misinterpreting nonspecific white-matter spots is a recognized diagnostic pitfall ^[7]. Here are clues specialists use to distinguish MS from other potential causes:

Migraine and Small-Vessel Disease

Many people with a history of severe migraines have small, nonspecific white-matter spots on their MRIs. Similarly, small-vessel disease—which is highly associated with aging, high blood pressure, and smoking—causes lesions that can look like MS ^{[8] [9]}.
Unlike MS, migraine and small-vessel lesions are usually punctate (tiny dots), are predominantly found in the deep subcortical white matter, and typically lack the classic Dawson’s finger shape ^[10]. Small-vessel disease may also present with microbleeds or small strokes (lacunes), which are not typical of MS ^[9]. However, these are clues rather than absolute rules, as severe small-vessel disease can occasionally mimic MS patterns.

Other Inflammatory Disorders (NMOSD and MOGAD)

Neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) are autoimmune diseases that can closely mimic MS but require different treatments.

• Spinal Cord and Optic Nerve Lesions: MS spinal cord lesions are usually short and located on the outer edges of the cord. In contrast, NMOSD often causes longitudinally extensive lesions that span three or more vertebral segments, as well as severe or bilateral optic nerve involvement ^{[11] [4]}.
• Brain Lesions: MOGAD lesions are often described as poorly demarcated or “fluffy,” unlike the sharper ovoid lesions of MS ^[12].
  Doctors use specific blood tests (anti-AQP4 and anti-MOG antibodies) to help identify these disorders, though results must always be interpreted alongside the clinical syndrome, as false positives and false negatives can occur.

Vitamin Deficiencies and Infections

• Metabolic/Nutritional: Deficiencies in vitamin B12 or copper can cause demyelination in the spinal cord. These often appear on an MRI as symmetric lesions in the back of the spinal cord (sometimes called an “inverted-V” sign), which is different from the typically asymmetric MS pattern ^{[13] [14]}.
• Infections and Spinal Fluid Testing: Lyme disease, HIV, and other infections can occasionally cause neurological symptoms and brain spots. Depending on your risk factors and symptoms, doctors may run blood work or perform a spinal tap (lumbar puncture) ^[15]. A spinal tap is also highly valuable for finding oligoclonal bands or kappa free light chains—markers of immune activity in the cerebrospinal fluid that strongly support an MS diagnosis ^[16].

Advanced Imaging: Central Veins and Iron Rims

When the diagnosis is unclear, specialists may use powerful MRIs with specialized sequences to look for advanced supportive markers:

• The Central Vein Sign (CVS): Because MS lesions form around tiny blood vessels, specialized scans can sometimes detect a distinct central vein running through the middle of an MS lesion. Migraine and small-vessel disease lesions typically do not have this ^{[17] [18]}.
• Paramagnetic Rim Lesions (PRLs): Some MS lesions develop a dark rim of iron on specialized imaging, indicating smoldering inflammation. Their presence is highly specific to MS and helps rule out mimics ^{[19] [18]}.

It is important to know that these advanced markers are supportive, not definitive. They require specialized scanning protocols that aren’t available everywhere, they are not required to diagnose MS, and the absence of these markers does not rule out MS ^[18].

The Importance of Clinical Correlation

The phrase “treat the patient, not the scan” is critical in MS. Clinical correlation means that the spots on the MRI must make neuroanatomical sense given your physical symptoms ^[2]. For example, if you have new vision loss in your right eye, but your MRI only shows old, non-enhancing spots in the area of the brain that controls your legs, the MRI does not explain your current symptom.

If you have an atypical presentation—such as being older at symptom onset, having significant vascular risk factors, or having vague symptoms that don’t match standard MS relapses—it is highly recommended to seek a second opinion from an MS specialist or a neuroradiologist ^[7]. They can review your symptoms alongside your scans and determine if further testing or “watchful waiting” (monitoring with structured, scheduled follow-up MRIs) is the safest approach.