Advances in MRI for the diagnosis of multiple sclerosis: A focus on radiological markers

The revised McDonald MS diagnostic criteria, published in September 2025, have already been “transformative”.

Professor of neurology at the University of Nottingham, Nikos Evangelou, said they were streamlining diagnosis and, with the addition of MRI-based biomarkers, helping to avoid the need for intrusive lumber puncture.

In this Neurology Academy webinar, speakers spoke about the neuroradiological elements of the updated criteria, explaining how to identify, interpret and report central vein sign (CVS) and paramagnetic rim lesions (PRL) in practice.

New diagnostic criteria: Radiology[i]

Explaining the rationale behind the update, Nikos explained that knowledge of MS and its biomarkers had increased significantly in recent years. It means we can “now get closer to a diagnosis of MS without a lumber puncture”, he said.

The diagnostic criteria are uniform, across all forms of MS, and MRI is central.

MS can be diagnosed from the point of clinically isolated syndrome (CIS) with evidence of lesions in four of five lesion locations: juxtacortical or cortical, periventricular, infratentorial, spinal cord, and optic nerve. “You do not have to wait for another relapse to occur or another lesion to develop,” said Nikos.

CVS, in six or more lesions, can be diagnostic, and PRL can be “very useful”, he added.

In the case of incidental imaging findings that are suggestive of demyelinating disease, the criteria recommend excluding other explanations. After this, if lesions are present in two or more central nervous system (CNS) sites, MS can be diagnosed if the patient demonstrates cerebrospinal fluid (CSF) positivity, CVS positivity or dissemination in time (DIT).

Similarly, where a patient has clinical symptoms of MS, and differential diagnoses are excluded, the condition can be diagnosed if:

• lesions are present in two or more CNS sites, or the patient has at least two CNS lesions and 12 months or more progression, and one of the following:
  • CSF positivity, CVS positivity, DIT, lesions In four or five CNS anatomical locations

If lesions are present in one CNS site, MS may be diagnosed if one of the following is also demonstrated:

• CSF and CVS positivity
• CSF and PRL positivity
• DIT and CVS positivity
• DIT and PRL positivity

Interpret and report

CVS is most commonly seen in periventricular and deep white matter MS lesions, and can look like coffee beans or doughnuts, explained Rob Dineen, professor of neuroradiology at the University of Nottingham.

The radiological definition is a thin hypointense line or small hypointense dot, visualised in two perpendicular MRI planes. The vein will have a diameter of < 2mm, and run centrally through the lesion. Exclusion criteria include the lesion being < 3mm in diameter in any plane, confluent lesions, or the lesion having multiple distinct veins or being poorly visible.

In practice, Rob said he examines SWI and FLAIR side-by-side. He marks off the CVS lesions with the aim of identifying six, in line with the MacDonald criteria ‘rule of six’. If there are fewer than this, the number is given on the MRI report.

Motion artefacts can be challenging, but it may still be possible to, cautiously, identity and count CVS, Rob explained. “If I see a few veins, I will report the number, but if may be necessary to repeat the scan if it is going to be critical to making that diagnosis,” said Rob.

The criteria for PRL, he went on, include identification of hypointensity of least two-thirds of the total rim, coinciding with the margin of a T2 hyperintense legion. It needs to be visible on ≥ 2 consecutive slides in 2D acquisitions, or two orthogonal planes in 3D acquisition. Contrast-enhancing lesions are not PRLs.

Imaging sequences

Pascal Sati, associate professor at Cedars-Sinai Medical Center in Los Angeles, shared his tips on imaging CVS and PRL. The “key thing”, he explained, was to use susceptibility-sensitive MRI sequences. “CVS and PRL are magnetic, so we need to use sequences that can detect this magnetism,” he added.

For CVS, that means susceptibility weighted imaging (SWI), T2* weighted, or FLAIR*. For PRL that means SWI, T2 weighted, and filtered phase. Pascal said that all of these are FDA-cleared and can be used on any of the clinical scanners, though not all vendors provide all options. Neither Siemans nor GE, for example, provide FLAIR, and some sequences require additional software.

In SWI, Pascal recommended a submillimetre axial in-plane resolution of 0.5 x 0.5 mm, and 3D acquisition of thin ≤ 3mm slices. PRL and CVS can be detected at field strengths from 7 T to 1.5 T.

CVS, however, is not always visible on SWI. Pascal recommended a side-by-side comparison with T2*-FLAIR, or optimising SWI with a flip angle (FA) of 5°, which “gives you the option to see both PSL and CVS on one image”.

There are limitations to the approach, primarily as signals can become blurry when views are rotated. T2*-weighted 3D echo-Planer imaging (3D-EPI) is a newer technique, with a higher resolution that is preserved in all rotational views. CVS and PRL are detectable on all field strengths.

FLAIR* combines T2-FLAIR and T2* 3D-EPI, and enables the easier detection of CVS in white matter lesions.

PRL lesions can be detected on T2-FLAIR, and Pascal recommended ensuring it was non-enhancing before moving to SWI to identify the characteristic dark ring. The next step is looking for convection on filtered phase SWI. “We recommend you looking for the right-handed convection, meaning both the vessels and the rim should be hypointense,” he explained.

He added that filtered phase T2* 3D-EPI also enabled detection of the convection detection, while also allowing the PRL to be visible in all planes. This way, “you can convince yourself it is a sphere, which is really what you are looking for,” he said.

[i] Montalban, X., Lebrun-Frénay, C., et al. (2025). Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. The Lancet Neurology, 24(10), 850-865.