What doctors look at on MRI scans in multiple sclerosis — a detailed guide

May 28, 2026

Exactly what radiologists and neurologists see on a brain and spinal cord MRI of someone with MS: T1, T2, FLAIR, contrast, "black holes", periventricular lesions, Dawson's fingers, atrophy, McDonald criteria, and how disease progression is tracked.

Why MRI is the most important test in multiple sclerosis

In conversations with people in the MS community, this is one of the questions that keeps coming back. Magnetic resonance imaging (MRI) is the most sensitive and most specific test for multiple sclerosis and other demyelinating diseases of the central nervous system. Unlike a CT scanner, MRI does not use X-rays — it uses a strong magnetic field (1.5T or 3T) and radio waves to display the difference between normal and damaged brain and spinal cord tissue. Without MRI, the modern McDonald 2017/2024 criteria for diagnosing MS are practically impossible to apply (Thompson 2018, Wattjes 2021). This article explains in detail exactly what radiologists and neurologists look at when they open your MRI scan, what the unfamiliar terms in the report mean, and why a scan can sometimes sound alarming while you actually feel well.

How MRI works — very briefly

The hydrogen atoms in the water of your tissue behave like tiny magnets. When you enter the scanner tunnel, they align with the magnetic field. A radio pulse knocks them out of alignment, and the time it takes for them to return depends on the type of tissue and the amount of water present. This recovery time is called T1 and T2 relaxation, and the differences in these times produce the various sequences we see. Myelin is a fatty substance; damaged myelin means more free water at that location — which the MRI "sees" as a bright or dark spot, depending on the sequence.

Main MRI sequences — what each one shows

T1 sequence (T1-weighted). Fat (myelin) is bright, water is dark. Normal white matter looks bright. "Black holes" — dark spots on T1 — represent areas of permanent axonal and myelin loss. The more black holes, the more irreversible damage. Persistent black holes (lasting more than 6 months) predict long-term disability (van Walderveen 1998, Sahraian 2010).

T2 sequence (T2-weighted). Water is bright. MS lesions appear as white/bright spots — this is what most people recognise as "spots on the brain". T2 lesion count increases over the lifetime of MS, but after a certain point it stops correlating with disability (the "T2 paradox").

FLAIR (Fluid Attenuated Inversion Recovery). A modified T2 sequence in which the cerebrospinal fluid is suppressed and appears black, while lesions remain bright. This is the key sequence for detecting periventricular lesions (around the brain ventricles) because it clearly separates them from the bright CSF. FLAIR is the gold-standard sequence for MS diagnosis.

DWI (Diffusion Weighted Imaging). Shows acute damage (most often stroke). In MS it is used to rule out a stroke that can mimic a relapse.

Post-contrast T1 (with gadolinium). After an injection of gadolinium contrast (Gd), active, fresh lesions with a broken blood-brain barrier become bright ("enhancing lesions"). A lesion typically enhances for 2–6 weeks after onset. An enhancing lesion means an active inflammatory phase — either symptomatic (relapse) or silent. More than one active lesion means active disease and is usually a signal to escalate therapy.

SWI / T2*. Detects the "central vein sign" — a small vein in the middle of a lesion that is highly characteristic of MS and helps distinguish it from migraine or vascular lesions (Sati 2016, NAIMS consensus).

Where exactly doctors look for MS lesions — anatomical zones

MS does not produce lesions randomly. The McDonald criteria require lesions in at least 2 of 4 typical zones, known as "dissemination in space" (DIS):

1) Periventricular lesions. Lesions immediately adjacent to the lateral ventricles. Typically oval, finger-like along veins emerging from the ventricles — the famous "Dawson's fingers", almost pathognomonic for MS on sagittal FLAIR. McDonald 2017 requires three or more periventricular lesions to count.

2) Juxtacortical / cortical lesions. Lesions at the junction of white and grey matter or within the cortex itself. Cortical lesions are best seen on 3T MRI with DIR or PSIR sequences. They correlate more strongly with cognitive decline than white-matter lesions.

3) Infratentorial lesions. In the cerebellum or brainstem (pons, medulla). Lesions here typically cause vertigo, double vision, dysarthria or ataxia.

4) Spinal cord lesions. The cervical spinal cord is most often affected. Typical MS lesions are short (< 2 vertebral segments), eccentric, peripheral, and involve less than half the cord cross-section. By contrast, lesions extending over 3 or more segments (LETM) point toward NMO/MOG, not MS.

Typical features of MS lesions — the "MS look"

Radiologists do not just count spots — they look at morphology. A typical MS lesion is:

oval or elliptical, with the long axis pointing toward the ventricles (Dawson's finger), well-circumscribed, not diffuse, 3–15 mm in size, without mass effect (does not push surrounding structures), often with a central vein visible on SWI, sometimes showing an "open ring" enhancement after contrast — an incomplete ring opening toward the cortex — very characteristic of MS and helpful in distinguishing it from tumours or abscesses (Masdeu 2000).

Dissemination in time (DIT) — McDonald criteria

To diagnose MS from a single MRI, there must be dissemination in time, meaning either:

- the simultaneous presence of an enhancing and a non-enhancing lesion on the same scan, OR

- a new T2 lesion or new enhancing lesion on a follow-up scan, regardless of timing.

After a first clinical event (CIS, *clinically isolated syndrome*), if MRI satisfies both DIS and DIT, the diagnosis of MS can be made immediately — without waiting for a second relapse (Thompson 2018, Montalban 2024 update).

Brain atrophy — the "silent" marker of progression

Beyond lesions, radiologists measure brain volume. Healthy people lose about 0.1–0.3% of brain volume per year after age 40. People with MS lose 0.5–1.5% per year, and this loss is the strongest predictor of long-term cognitive and physical disability (De Stefano 2016). Atrophy of the thalamus and cortical grey matter is especially important — it begins early, even before clinical symptoms appear. Volumetric tools (NeuroQuant, Icometrix, SIENA) are increasingly entering routine practice.

Spinal cord atrophy

Thinning of the cervical spinal cord, especially at the C2–C3 level, is a strong early marker of progression to SPMS. It is often visible before progression is clinically confirmed (Lukas 2015).

What is NOT MS on MRI — differential diagnosis

Many white-matter spots are not MS. The radiologist always considers:

Vascular (ischemic) lesions — typically in people over 50 with hypertension, diabetes, or smoking. Located in deep white matter and basal ganglia, not adjacent to the ventricles. No contrast enhancement, no central vein.

Migraine white spots — small, superficial, without an oval shape, without Dawson's fingers, without contrast enhancement. Very common in migraine with aura — and very often mistaken for MS in young women.

NMOSD (neuromyelitis optica spectrum disorder) — long spinal lesions (≥ 3 segments), large confluent hemispheric lesions, area postrema involvement. Positive AQP4 antibodies.

MOGAD — bilateral optic neuritis, ADEM-like large lesions in children, positive MOG antibodies.

Vasculitis, sarcoidosis, Lyme disease, B12 deficiency, leukodystrophies — each produces a distinct pattern.

Tracking therapy — the NEDA-3 concept

The goal of modern DMT is NEDA-3 (No Evidence of Disease Activity): no relapses, no EDSS progression and no new or enlarging T2 lesions and no enhancing lesions on MRI. If your annual MRI shows new lesions despite therapy, that is a signal the treatment is not working well enough — and a reason to discuss escalation. More: [signs MS is progressing](/blog/znaci-napredovanje-ms-progression).

How MRI is performed in MS — practical details

Duration: 30–60 min for the brain, 60–90 min for brain + spinal cord.

Contrast: gadolinium (Gd) is given intravenously when active lesions are being sought. Modern macrocyclic agents (gadobutrol, gadoterate) carry very low risk. Older linear agents have been withdrawn because of dentate-nucleus accumulation.

Standard MS protocol (MAGNIMS / CMSC): sagittal FLAIR, axial T2, axial FLAIR, 3D T1 pre- and post-contrast, DWI; for the cord — sagittal T2, STIR, post-Gd T1 (Wattjes 2021).

Magnet strength: 3T offers higher resolution and better detection of cortical lesions, but 1.5T is fully acceptable for routine follow-up.

Frequency: Baseline MRI at diagnosis → repeat at 3–6 months → then once a year for the first 2–3 years on DMT, then as clinically needed.

How to read your own report — common terms

"Hyperintense T2/FLAIR lesions supratentorially, periventricular and juxtacortical" — bright spots around the ventricles and at the cortex — a typical MS pattern.

"No post-contrast enhancement" — no active lesions at the time of the scan. Good news.

"Stable findings compared to previous MRI" — no new lesions. Very good news, meaning the therapy is working.

"Three new T2 lesions compared with MRI from 2025." — active disease, time to discuss DMT escalation.

"Mild diffuse cortical atrophy appropriate for age" — common, not a catastrophe.

"T1 hypointensities (black holes) in the corona radiata" — areas of permanent damage. Their number is tracked year to year.

What MRI CANNOT do

MRI does not directly measure pain, fatigue, cognitive function or quality of life. You can have an alarming-looking scan and feel well ("clinico-radiological paradox") or the reverse — few lesions and severe symptoms. The report must always be interpreted by a neurologist in the context of the clinical picture.

Practical tips for patients

1) Always request your scan on a CD or USB, not just the printed report — the neurologist needs to compare with previous MRIs.

2) Try to scan at the same centre and on the same magnet strength whenever possible — comparability is crucial.

3) Bring your old scans to every appointment — without comparison, "new" cannot be defined.

4) Before scanning, tell the staff about: cochlear implants, pacemakers, metal clips, pregnancy, kidney problems (because of contrast), claustrophobia.

5) If you have claustrophobia, ask for an open MRI or a mild sedative — better than missing the scan.

6) Do not panic about "many lesions" — lesion count alone does not determine the course of disease. Location, atrophy, spinal cord involvement and treatment response carry more weight.

MRI is a window into your MS. Doctors simultaneously look at: where lesions are (periventricular, juxtacortical, infratentorial, spinal), how they look (Dawson's fingers, central vein, "open ring" enhancement), how many are new compared with the prior scan, whether they are active (enhancing with contrast), whether there are black holes (permanent damage), and whether the brain and cord are atrophying. All of that feeds into the assessment of whether the disease is quiet (NEDA-3) or whether it is time to change therapy. Understanding your own report makes you an active partner in your care. More: [DMT medications for MS](/blog/dmt-lekovi-multipla-skleroza-2026), [EDSS calculator](/edss-kalkulator), [signs MS is progressing](/blog/znaci-napredovanje-ms-progression), [MS glossary](/blog/ms-recnik-medicinski-termini-multipla-skleroza).

Sources

Thompson AJ, et al. "Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria." Lancet Neurol. 2018: https://pubmed.ncbi.nlm.nih.gov/29275977/. Wattjes MP, et al. "2021 MAGNIMS-CMSC-NAIMS consensus recommendations on the use of MRI in patients with multiple sclerosis." Lancet Neurol. 2021: https://pubmed.ncbi.nlm.nih.gov/34139157/. Sati P, et al. "The central vein sign and its clinical evaluation for the diagnosis of multiple sclerosis: a consensus statement from the NAIMS." Nat Rev Neurol. 2016: https://pubmed.ncbi.nlm.nih.gov/27834394/. Filippi M, et al. "MRI criteria for the diagnosis of multiple sclerosis: MAGNIMS consensus guidelines." Lancet Neurol. 2016: https://pubmed.ncbi.nlm.nih.gov/26822746/. De Stefano N, et al. "Establishing pathological cut-offs of brain atrophy rates in multiple sclerosis." J Neurol Neurosurg Psychiatry. 2016: https://pubmed.ncbi.nlm.nih.gov/26511902/. van Walderveen MA, et al. "Histopathologic correlate of hypointense lesions on T1-weighted spin-echo MRI in multiple sclerosis." Neurology. 1998: https://pubmed.ncbi.nlm.nih.gov/9818853/. National MS Society — MRI: https://www.nationalmssociety.org/Symptoms-Diagnosis/Diagnosing-Tools/MRI. MS Trust — MRI scans: https://mstrust.org.uk/a-z/mri-scans. This article is informational and does not replace interpretation of your MRI report by a neurologist and radiologist.