The Diagnostic Toolkit: MRIs, Tests, and Monitoring

Confirming a diagnosis of progressive MS is a detailed process that looks at your history, physical exams, and imaging. Because the changes in progressive MS are often gradual, doctors use a specific set of rules called the McDonald Criteria to ensure they have the right diagnosis ^[1]. In 2024, these rules were updated to make the process faster and more accurate ^[2].

The Rulebook for Diagnosis

To be diagnosed with Primary Progressive MS (PPMS), you typically must have at least one full year where your symptoms have steadily worsened ^[1]. Additionally, your doctor looks for objective evidence of the disease using specific dissemination-in-space lesion locations and numbers, defined CSF findings, and the exclusion of alternative diagnoses. This involves specific combinations of evidence from the brain, spinal cord, or optic nerve, or evidence from spinal fluid (a lumbar puncture) showing oligoclonal bands or a high kappa free-light chain index ^[1][3][4]. These criteria must be applied by a clinician after considering mimics; patients should not self-apply them.

Decoding Your MRI Report

An MRI is the most powerful tool for “seeing” MS. When you read your report, you will see several technical terms that describe different aspects of the disease:

• T2 Hyperintense Lesions: These are bright spots that show where damage or scarring has occurred at any point in the past ^[5]. However, these are not specific to MS and can occur with aging or migraines.
• Gadolinium-Enhancing (T1) Lesions: These are spots that “light up” when a contrast dye is used during the scan. They indicate a recent breakdown of the blood-brain barrier rather than necessarily inflammation occurring at the exact moment of scanning ^[5].
• T1 Hypointense Lesions (‘Black Holes’): These are dark spots that represent areas where chronic tissue loss has occurred, though they are not invariably permanent ^[6].
• Atrophy (Volume Loss): This refers to the gradual shrinking of the brain or spinal cord over time. In progressive MS, spinal cord atrophy is often more closely linked to physical disability than brain lesions are ^[7][8].

New Markers of Progression

Researchers are now using “advanced” MRI findings to find the “smoldering” inflammation typical of progressive MS:

• Slowly Expanding Lesions (SELs): Pre-existing spots that grow slowly outward like a ripple in a pond ^[9].
• Paramagnetic Rim Lesions (PRLs): Also called iron-rim lesions, these have a dark edge of iron-containing immune cells, signaling a site of chronic, ongoing damage ^[10].

These are active research concepts and generally require specialized sequences not consistently reported in routine practice.

Tracking Your Progress: Beyond the MRI

While MRIs show the anatomy, physical tests show how you are functioning. Your doctor will likely use the Expanded Disability Status Scale (EDSS), a 0–10 score based on your neurological exam ^[11].

Because the EDSS is heavily focused on walking, many specialists now use a “composite” of three tests to get a fuller picture ^[11]:

1. Timed 25-Foot Walk (T25FW): A simple measure of walking speed ^[12].
2. 9-Hole Peg Test (9HPT): A timed test of hand dexterity ^[13].
3. Symbol Digit Modalities Test (SDMT): A quick test of “processing speed” or how fast your brain can handle information ^[14].

Worsening that is confirmed on these tests after 3 or 6 months—using a specified method to rule out a relapse or test variability—is known as Confirmed Disability Progression (CDP) ^[15].

The Future: Blood Biomarkers

You may hear about a blood test for Neurofilament Light (NfL). NfL is a protein that leaks into the blood when nerves are damaged ^[16]. While it isn’t used to diagnose MS yet, it is becoming a valuable tool for tracking how “active” the disease is and how well a treatment is working ^[17].

Questions for Your Specialist About Your MRI

When reviewing your records, you might ask your doctor if these details are relevant for your specific scan protocol:

• Comparison to Previous Scans: Are lesions new, larger, or stable?
• Spinal Cord Imaging: Is imaging the cervical (neck) portion useful given my symptoms? ^[7]
• Contrast Use: Is gadolinium necessary for this specific follow-up to check for a recent blood-brain barrier breakdown? ^[5]
• Brain Locations: Are there findings in the periventricular, cortical, or infratentorial areas? ^[1]
• Atrophy Qualitative Assessment: Do brain or cord volumes appear normal for my age? ^[8]