McDonald 2024 diagnostic criteria for multiple sclerosis in a nutshell –⁠ a neurologist’s and radiologist’s perspective

Overview

The McDonald criteria represent the fundamental diagnostic tool for multiple sclerosis. The 2024 revision enables diagnosis similarly to the 2017 revision, but expands diagnostic options with changes that reflect the current understanding of the disease as a biological continuum. It unifies the diagnostic approach for both relapsing and primary progressive forms, adds the optic nerve as the fifth anatomical location for assessing dissemination in space, and includes the kappa free light chain index as an equivalent alternative to oligoclonal bands. The updated criteria introduce new, highly specific MRI markers –⁠ the central vein sign and paramagnetic rim lesions –⁠ which improve diagnostic specificity, particularly in atypical populations. However, detection of these new markers is strongly dependent on the MRI sequence used, and their assessment may be time-consuming. The most significant change is the possibility of establishing a diagnosis in the preclinical phase in asymptomatic patients or patients with atypical symptoms. However, the current Czech reimbursement criteria require clinical activity to initiate therapy, which limits therapeutic options in this population and increases pressure to map the epidemiological situation early and negotiate with healthcare payers. Successful implementation of the criteria also depends on standardization of imaging methods, raising awareness in the broader medical community, availability of advanced diagnostics, and close collaboration between neurologists and radiologists. This article aims to provide a practical overview of the changes from the perspective of both neurologist and radiologist, including diagnostic algorithms to facilitate the use of the criteria in routine clinical practice.

Keywords:

Multiple sclerosis – Optic nerve – kappa free light chains – radiologically isolated syndrome – McDonald diagnostic criteria – subclinical multiple sclerosis – central vein sign – paramagnetic rim lesion

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.

Introduction

One of the hottest topics in neurology is the new McDonald 2024 diagnostic criteria for MS [1]. They represent a logical continuation of the previous revision from 2017 [2] and respond to a fundamental shift in our understanding of the etiology and pathophysiology of MS, as well as to advances in paraclinical methods. Their goal is to enable earlier and more sensitive detection of the disease while maintaining specificity, as well as to bring neuroimmunology into the modern era of diagnosis based on the biological nature of the disease. While the new criteria allow for diagnosis according to the previous criteria, they also expand the scope of diagnosis and present a number of challenges. They emphasize the role of MRI and other biomarkers and, among other things, introduce the possibility of diagnosis prior to the development of clinical symptoms. This brings to the forefront the necessity of close collaboration between neurologists and radiologists, as well as the standardization of examination protocols and structured reporting [3,4]. The aim of this review article is to summarize the main changes in the 2024 McDonald criteria compared to the 2017 version, to provide a practical summary of key points from the perspectives of both neurologists and radiologists, and to assess their impact on daily clinical practice.

 

Seven years, seven major changes: key updates to the 2024 criteria

Seven years of intensive research have passed since the publication of the previous revision of the McDonald criteria [2], yielding new insights and advancing diagnostic capabilities. The result is the 2024 revision [1] (published in late 2025), which represents more than just a technical update—it is a paradigm shift in the understanding of MS as a continuum of biological processes from preclinical stages to overt disease. The most significant changes can be summarized in the following areas (Table 1).

 

1. Uniform criteria for both primary progressive and relapsing-remitting MS

The first major change is the standardization of the new criteria for both relapsing-remitting MS (RRMS) and primary progressive MS (PPMS). This reflects the current understanding of this variable disease as a continuum in which the relative contributions of individual pathophysiological mechanisms vary between individuals and over time [5].

 

2. Two spinal lesions are sufficient for spatial dissemination (DIS) in PPRS

The only exception to the above rule is the fulfillment of DIS in patients with PPRS in the presence of at least two spinal lesions. This change reflects the more frequent spinal predominance in progressive MS and significantly facilitates its diagnosis. However, caution is required when interpreting isolated spinal findings, as a number of other progressive neurological diseases (e.g., hereditary spastic paraparesis, metabolic myelopathies, etc.) may present similarly [6–8].

 

3. The optic nerve as the fifth site

Another groundbreaking change is the inclusion of the optic nerve as the fifth site for DIS assessment (in addition to the spinal, infratentorial, periventricular, and juxta/cortical sites). Given that retrobulbar neuritis is among the first manifestations in up to 25% of patients, this change was a logical step [9]. Furthermore, the lesion can be detected not only on MRI but also using two other modalities: optical coherence tomography (OCT) or visual evoked potentials (VEP). For OCT, the criterion is an interocular difference of ≥ 6 µm in the peripapillary retinal nerve fiber layer (pRNFL) or ≥ 4 µm in the medial ganglion cell inner layer (mGCIPL) [10–12]. For VEP, evidence of demyelinating involvement is indicated by prolonged P100 latency or asymmetric interocular latency (> 2.5 standard deviations above normal) [13].

 

4. Dissemination over time (DIT) is no longer a requirement

While the 2017 McDonald criteria [2] allowed DIT to be met or replaced by the presence of oligoclonal bands (OCBs) in cerebrospinal fluid, the 2024 revision goes even further. A diagnosis can now be established without evidence of temporal dissemination if other specific conditions are met—e.g., involvement of four or more anatomical sites [1]. This change represents a further advancement in the possibilities of early diagnosis and shortens diagnostic latency.

 

5. “Subclinical MS”

When discussing the reduction of diagnostic latency, another crucial development is the ability to diagnose MS in the absence of typical clinical symptoms, or even during the preclinical phase of the disease. However, the criteria for diagnosing subclinical MS are not identical to the diagnostic criteria for radiologically isolated syndrome, although they largely overlap (see below). Theoretically, a situation may arise, for example, in which a previously asymptomatic patient does not meet the criteria for radiologically isolated syndrome (RIS) but does meet the criteria for MS [1,14].

 

6. Specific MRI features (central venule sign –⁠ CVS, paramagnetic rim of the lesion –⁠ PRL)

Lowering the threshold and simplifying the diagnosis of MS without adding specific features could lead to a decrease in specificity. Therefore, in some situations, these specific MR features are required when fewer of the already known disease characteristics are met. The first of these is CVS—CVS positivity occurs in the presence of at least 6 lesions with CVS, or a predominance of CVS-positive lesions when there are fewer lesions (< 10). The second marker is the presence of at least one lesion with PRL. PRLs reflect chronic inflammatory activity at the lesion margin and are detectable by on susceptibility-weighted sequences in phase imaging (SWI, QSM). CVS and PRL are thus becoming part of routine diagnosis and increase its specificity. However, the absence of these specific features does not rule out a diagnosis of MS.

 

7. Kappa free light chain index (kFLC) as an equivalent alternative to OCB

OCBs are now the gold standard in diagnostics. However, their determination by isoelectric focusing with immunodetection is time-consuming (the assay itself takes approximately 4 hours) and requires specialized expertise, thus limiting its availability. In contrast, the kFLC index represents a faster, cheaper, and assessor-independent alternative to OCB. kFLC measurement by nephelometry or turbidimetry can be performed within 30 minutes at a fraction of the cost [15–17]. A systematic meta-analysis of 32 studies involving over 3,300 patients with clinically isolated syndrome (CIS) and MS demonstrated comparable diagnostic accuracy between the two methods—the kFLC index has a sensitivity of 88% and a specificity of 89%, which is entirely comparable to OCB (sensitivity 85%, specificity 92%) [18]. Agreement between the two methods is approximately 87–90% [19]. Incorporating the kFLC index into the diagnostic algorithm as an equivalent alternative to OCB can thus improve both the speed and accessibility of diagnosis, even in countries with limited access to specialized laboratory methods.

 

Special populations require a specific approach

The 2024 criteria also systematically address diagnostic challenges in children, older patients, and individuals with comorbidities for the first time, thereby improving diagnostic safety in these high-risk groups. The same diagnostic framework applies to children and adolescents as to adults; however, in patients presenting with acute disseminated encephalomyelitis (ADEM), the criteria cannot be applied without further follow-up, and a diagnosis of MS requires a second clinical attack or new T2 lesions more than 90 days after the onset of ADEM [1]. Given the higher prevalence of disease associated with antibodies against myelin oligodendrocyte glycoprotein (MOGAD) in the pediatric population, testing for MOG-IgG antibodies using a cell-based assay is strongly recommended for all children under 12 years of age with a first demyelinating episode. In older children, testing for these antibodies is recommended in cases of atypical presentation [1,20,21]. For evaluating the CVS in patients under 18 years of age, given the often high lesion burden, the criterion of positivity in more than 50% of lesions is used instead of the rule of six [1,22]. There is also an increased risk of misdiagnosis in patients at the opposite end of the age spectrum—those over 50 years of age and those with comorbidities [1,23–25]. Risk factors include small-vessel ischemic disease, migraine and other headaches, psychiatric disorders, and certain autoimmune diseases [1,23,24,26]. For example, periventricular or cortical/juxtacortical lesions occur in up to one-third of patients with migraine, which can mimic the presentation of MS [27,28]. For these high-risk patients, the 2024 criteria strongly recommend additional testing to confirm the diagnosis: evidence of a spinal cord lesion, positive CSF, or CVS [1].

This evolution of the criteria responds to the need for earlier and more accurate diagnosis in the era of highly effective therapies [29,30]. At the same time, however, it places new demands on interdisciplinary collaboration and the technical equipment of medical facilities. In the following chapters, we will examine the practical implications of these changes from the perspective of a neurologist and a radiologist.

 

Through the Eyes of a Radiologist

As mentioned above, MR imaging plays an even more significant role in the new revision of the McDonald criteria than it did in previous versions, particularly in three aspects—the first is the incorporation of highly specific features in MR images (CVS and PRL), enabling both an increase in specificity even for discrete findings and, above all, an improvement in differential diagnosis, particularly in older patients or those with comorbidities. The second key new aspect is the inclusion of a fifth site for DIS evaluation—the optic nerve—and the third, no less important, is the possibility of diagnosing MS in the preclinical stage, thus highlighting the absolutely crucial role of MRI (Fig. 1).

In the case of the central venule sign, a small central venule is visible in the plaque area on susceptibility-weighted sequences, either in axial views—where it is often likened to an American doughnut—or in horizontal views, where it appears as a coffee bean. However, CVS has its limitations. The main one is that it is not a completely specific feature. CVS may also be present in other pathologies—particularly vasculopathies—but in a smaller percentage of lesions than in MS. To meet this specific diagnostic criterion, however, it is necessary to detect at least six lesions or, if fewer, the majority of lesions, with the presence of at least six lesions with CVS having 83–98% specificity [1,31–34]. The exact criteria [35] for evaluating this feature are listed in Table 2.

Another specific feature is the presence of a hyposignal border at the edge of the lesion on a susceptibility-weighted sequence. This border reflects the presence of activated microglia/macrophages with accumulated iron at the periphery of chronically active lesions and is observed on initial MR examination in approximately 46% of patients with subsequently confirmed MS [36]. Meeting the PRL criterion—i.e., the presence of at least one such lesion—shows high specificity for MS, reaching up to 90–98% [1,37,38], provided that the precise evaluation criteria listed in Table 3 are followed.

Both of these specific features depend on a sufficiently sensitive sequence. According to recommendations, T2* 3D echoplanar imaging and optimized SWI sequences are used; CVS is visible on magnitude images, and PRL on phase images [35,39]. For both features, examination on a 3T scanner is more sensitive; however, they are also detectable on a 1.5T scanner with appropriately selected sequence parameters. It should be noted that evaluation of these features is recommended and that they are part of the criteria; however, the inability to evaluate them (e.g., due to scanner limitations) does not preclude the diagnosis of the disease using MRI [1]. Evaluating these specific features is time-consuming; they must be assessed on the thinnest possible slices—for example, with 3D EPI, acquisition involves over 250 slices. A phase image is not always available on the evaluation console; sometimes post-processing using filters is necessary to remove artifacts in the phase image, which is problematic for use in clinical practice.

For the evaluation of the new, fifth, site for DIS assessment—the optic nerve—an MR image is not the only requirement; DIS can also be met using VEP or OCT. On MRI, we should always pay attention to this site, even when a detailed examination of the optic nerve is not included (T2-weighted fat-suppressed [FS] image or short tau inversion recovery and post-contrast examination with FS covering the chiasm). The lesion can also be very well detected in the double inversion recovery (DIR) or fluid-attenuated inversion recovery (FLAIR) sequences with fat suppression, both in 3D, which are used to detect lesions in brain tissue (Fig. 2) [1,40].

Last but not least, it is important to mention another groundbreaking development: the ability to diagnose MS in the preclinical stage, based primarily on MRI findings and potentially supplemented by positive detection in cerebrospinal fluid. Here, MRI is the tool that helps identify patients at risk, and in some cases, it directly aids in diagnosing radiologically isolated syndrome (valid criteria from 2023 [14]) or subclinical MS ( ). In this context, it is absolutely crucial to evaluate DIS with great precision. Juxtacortical lesions on the MR image must be in direct contact with clearly identified cerebral cortex, which also applies to cortical lesions. Periventricular lesions, in turn, must be in clear contact with the ependyma. Only lesions at least 3 mm in size with clearly differentiated margins are included in the MR criteria. The use of contrast agents remains crucial for diagnosis, even though the DIT criterion has been de-emphasized. This is because, given the typical shape of post-contrast enhancement (nodular, ring-shaped, and incomplete ring), it continues to be of fundamental importance in differential diagnosis and is also important for the diagnosis of RIS and subclinical MS. Furthermore, it is a significant negative prognostic marker that helps identify patients at risk of a more severe disease course.

It is also important to mention spinal cord imaging, which has long been part of the revised criteria. From an MRI perspective, however, it is necessary to emphasize the high specificity of spinal lesions, whose typical MRI appearance aids in differential diagnosis, and the fact that they represent a very strong predictive marker of a more severe disease course [41]. Furthermore, in the new criteria, two spinal lesions are sufficient to meet the DIS in patients with a progressive course [1].

To maximize the potential of MRI, it is necessary to use a sufficiently sensitive MRI protocol. The use of a standardized protocol enables the earliest possible diagnosis and also facilitates consistent communication across MS centers and collaborating MRI facilities [3,4,40]. From a practical standpoint, it is also essential that the radiologist raise suspicion of a demyelinating disease even in cases where the findings do not meet RIS criteria (e.g., DIS without spinal involvement)—such a patient could, if other conditions are met (e.g., OCB), immediately meet the criteria for subclinical MS. The threshold for recommending further testing should therefore be low.

 

From a neurologist’s perspective

From a neurologist’s perspective, the 2024 criteria represent a relatively significant shift in perspective. First and foremost, they expand the possibilities for earlier diagnosis [1,30,42]. One of the first validation studies shows that applying the new criteria increases the proportion of patients diagnosed at the initial examination from 63% to 80% and reduces the median time to diagnosis by approximately half [43]. Given the importance of initiating therapy as early as possible, this change may bring about a further improvement in the prognosis for patients with MS.

However, an even more significant implication of the new criteria for the future may be the possibility of making a diagnosis in the preclinical phase—that is, in patients without typical symptoms, often with incidental findings on MRI. Here, the focus shifts to paraclinical methods, including specific markers not yet routinely used (such as CVS, PRL, or the kFLC index), and requires careful differential diagnosis [44] as well as close multidisciplinary collaboration. It is also essential to establish an organizational structure that enables the timely referral of patients to an MS center equipped with an appropriate specialized MRI facility. This is linked to the need for sufficient awareness of this issue not only among radiologists but also among outpatient neurologists and other referring specialists who are the first to encounter incidental findings.

The inclusion of the optic nerve as the fifth site highlights the role of VEP and OCT—methods that have not yet been routinely used in MS diagnosis in the Czech context [12]. Last but not least, purely practical questions arise: what is the incidence of patients without clinical manifestations, to what extent should these patients be examined, what are the therapeutic implications, and finally—what will be the ultimate burden on the entire system?

 

The Diagnostic Algorithm in Practice

First, it must be emphasized that if a patient meets the 2017 McDonald criteria (i.e., DIS and DIT), the diagnosis of MS remains valid. The only exception—which is largely irrelevant in our context—is the fact that a diagnosis of MS can no longer be established based solely on the clinical picture (unless there is an absolute contraindication to imaging). The 2017 criteria theoretically allowed for a diagnosis to be made with ≥ 2 clinical attacks demonstrating clinical dissemination in space and time without the need for MRI, although imaging was strongly recommended. The new criteria eliminate this possibility, and paraclinical examination is now always required [1,2].

The possibility of DIS has been expanded to include a fifth area—the optic nerve—whose examination (whether by MRI, VEP, or OCT) should become part of the diagnostic process. DIT can be met as before by positive cerebrospinal fluid findings, which now include not only OCB but also the kFLC index—its determination should also become routine. Once DIS and DIT are met as defined above, a clinical attack is no longer necessary—a revolutionary change that places high demands on the quality and standardization of paraclinical examinations as well as on differential diagnosis [3,4].

In addition, there is a growing trend toward recommending a targeted MRI protocol that captures specific features (CVS, PRL). A positive CVS result can, in fact, replace DIT in patients with DIS, even in those without typical clinical symptoms. A properly performed MRI, aided by these new features, can then enable a diagnosis even in symptomatic patients for whom it was previously impossible: both in patients with a typical clinical presentation and lesions in 4–5 regions regardless of cerebrospinal fluid findings or DIT, and in patients with typical clinical symptoms but with lesions in only one area—provided they simultaneously meet DIT criteria (including OCB or kFLC positivity) and have CVS or PRL positivity (Table 4) [1,2].

However, the size of these newly defined patient groups—whether in terms of subclinical MS or those newly meeting the criteria for clinical MS—is a question that can only be answered through careful monitoring of real-world clinical practice.

 

Subclinical MS and RIS –⁠ where is the line?

Another question that arises with the new criteria is the significance of RIS. Do all patients with RIS automatically become patients with MS? The 2023 RIS criteria [14] require an asymptomatic patient with an incidental MRI finding in at least one of four typical regions (juxtacortical/cortical, periventricular, infratentorial, spinal) plus fulfillment of two of three conditions: OCB, spinal lesion, or DIT; alternatively, the older Okuda criteria may be met (fulfilling three of four conditions: ≥ 1 gadolinium-enhancing lesion or ≥ 9 T2 lesions; ≥ 1 infratentorial lesion; ≥ 1 juxtacortical lesion; ≥ 3 periventricular lesions) [45,46]. Subclinical MS also includes asymptomatic patients or patients with nonspecific symptoms, but different criteria are required for its diagnosis (Table 4). In practice, three situations may arise:

RIS without MS: an asymptomatic patient meeting RIS 2023 (e.g., lesions in one region—spinal + OCB), but who does not meet the criteria for subclinical MS (requiring lesions in 2 of 5 regions);

MS without RIS: e.g., DIS (without a spinal lesion) + OCB;

Both RIS and MS simultaneously (approximately 62% of patients with RIS according to the original Okuda criteria from 2009 would now meet the McDonald criteria for MS [1,45]).

 

Therapeutic implications

For patients with a typical first clinical attack, the situation is straightforward—those who previously did not meet the 2017 criteria but now do can be treated using standard protocols. More complicated is the question of how to proceed with patients with atypical symptoms or asymptomatic patients in whom subclinical MS is suspected—whether or not they meet the RIS criteria. A patient with an incidental finding suggestive of demyelination should be referred for standardized MRI imaging and, if suspicion persists, to a facility with an MS center. Given the lowered diagnostic threshold, thorough differential diagnosis is essential. Particularly in patients who may meet the criteria for subclinical MS, it is advisable to perform cerebrospinal fluid analysis and visual pathway testing (MRI/VEP/OCT), or other supportive or diagnostic markers. The goal is to confirm or rule out the diagnosis while simultaneously stratifying risk.

However, in the group of patients without typical symptoms, we face a fundamental problem stemming from the discrepancy between medical reality and reimbursement criteria. Current Czech reimbursement criteria require clinical activity—that is, a prior relapse or progression—to initiate treatment with disease-modifying therapy (DMT). A patient with RIS or subclinical MS thus does not meet the standard criteria, even though biologically it is the same disease as in patients with clinically manifest MS. Published data clearly demonstrate that this is a high-risk group—more than half of patients with RIS develop clinical symptoms within 10 years of follow-up [47]. The risk of conversion to clinically manifest MS directly depends on the presence of prognostic factors, which include age under 37 years, spinal or infratentorial lesions, gadolinium-enhancing lesions, and OCB positivity [48]. A key argument for early intervention is the results of two randomized trials that demonstrated significant efficacy of treatment in the preclinical stage: the ARISE trial with dimethyl fumarate achieved an 82% reduction in the risk of clinical conversion [49], while the TERIS trial with teriflunomide achieved a 72% adjusted reduction in this risk [50].

Therefore, even though standard reimbursement is not yet possible, thorough examination and monitoring of asymptomatic patients is warranted. First, for high-risk patients, reimbursement for treatment can be requested under Section 16 based on the results of the ARISE and TERIS studies. For those at lower risk, it is advisable to identify risk factors, including, for example, treating hypovitaminosis D [51]. Second, educating patients about possible symptoms and regular monitoring will enable early detection of clinical conversion and prompt initiation of therapy. And third, mapping the epidemiological situation will provide the data necessary for negotiations with payers regarding a revision of reimbursement criteria.

 

Conclusion

The 2024 McDonald criteria represent a fundamental evolutionary step in the diagnosis of MS, reflecting the current understanding of this disease as a biological continuum ranging from preclinical stages to manifest forms. The addition of the optic nerve as the fifth site, the unification of the diagnostic framework for both relapsing and progressive MS, the introduction of highly specific MRI features (CVS and PRL), and the equal inclusion of the kFLC index alongside OCB significantly expand diagnostic options and enable earlier and more accurate diagnosis. The most significant paradigm shift, however, is the possibility of establishing a diagnosis in the preclinical phase of the disease, i.e., in asymptomatic patients or patients with atypical symptoms. This step places entirely new demands on the organization of care, including the standardization of MR protocols, the availability of specialized imaging methods (OCT, VEP, susceptibility-weighted MR sequences), and, above all, close interdisciplinary collaboration between neurologists, radiologists, and other specialists.

In the Czech context, several practical challenges arise. First, it is necessary to ensure the availability and standardization of advanced diagnostic methods across MS centers. Second, it is essential to educate the broader medical community about the possibility of preclinical diagnosis so that patients with suspicious findings are referred in a timely manner for specialized testing. And third, it is necessary to open a discussion on revising reimbursement criteria, which currently do not allow for the initiation of DMT in patients without clinical activity, even though biologically it is the same disease and data from randomized trials clearly demonstrate the benefits of early intervention.

The 2024 criteria thus pave the way for more personalized medicine based on the biological nature of the disease rather than on clinical manifestations. Their full implementation into clinical practice will require time, technical resources, and systemic changes, but the potential benefit for patients in the form of earlier diagnosis and initiation of therapy is undeniable.

 

Grant support

Supported by a program project of the Ministry of Health of the Czech Republic (reg. no. NW26J-08-00103), a grant from the Ministry of Health of the Czech Republic (RVO-VFN64165), and the Cooperatio research program at Charles University, neuroscience.

 

Conflict of Interest

The authors declare that they have no conflict of interest in connection with the subject of this work.

 

Table 1. Summary of differences between the 2017 and 2024 revisions of the McDonald criteria [1,2].

Area	2017 Criteria	2024 Criteria
Primary progressive MS	standalone criteria 12-month progression + 2 of 3: ≥ 1 brain lesion in at least 1 of 3 regions –⁠ juxtacortical/cortical, infratentorial, periventricular ≥ 2 spinal lesions Intrathecal OCB synthesis	Unified criteria 12-month progression + fulfillment of the same criteria as for relapsing MS; 2 spinal lesions are sufficient to meet DIS criteria
Number of anatomical regions for DIS	4 –⁠ periventricular, infratentorial, juxtacortical/cortical, spinal	5 –⁠ optic nerve added (based on OCT/VEP/MRI)
DIT required	evidence of a new lesion/relapse is required; alternatively, intrathecal OCB synthesis may be used instead of DIT	DIT may be replaced, depending on the specific situation, by numerous biomarkers or combinations thereof (OCB, kFLC index, CVS, PRL)
Specific MR features	Not applied	Introduced: CVS and PRL
MRI finding suggestive of MS	Evaluated outside the scope of the McDonald criteria	Included in the unified diagnostic framework for MS; diagnostic criteria for MS can be met even without characteristic clinical findings
CSF biomarkers	OCB only	OCB or kFLC index (equivalent alternatives)
Consideration of age and comorbidities	minimum recommendation	In patients ≥ 50 years of age or with high-risk comorbidities, additional criteria are recommended to confirm the diagnosis (spinal lesion, positive CSF, CVS)
Pediatric diagnosis	ADEM distinguished, no uniform framework	Uniform framework as in adults; <12 years: MOG-IgG strongly recommended for all; ≥ 12 years: MOG-IgG in cases of atypical presentation; for ADEM, a subsequent attack or new T2 lesions with a latency of ≥ 90 days are required; for CVS, ≥ 50% of lesions are required

ADEM –⁠ acute disseminated encephalomyelitis; CSF –⁠ cerebrospinal fluid; CVS –⁠ central venule sign; DIS –⁠ spatial dissemination; DIT –⁠ temporal dissemination; kFLC –⁠ kappa free light chains; MOG-IgG –⁠ antibodies against myelin oligodendrocyte glycoprotein; OCB –⁠ oligoclonal bands; OCT –⁠ optical coherence tomography; PRL –⁠ paramagnetic rim of the lesion; VEP –⁠ visual evoked potentials

 

 

Table 2. Definition of a lesion with central venule sign [35].

Criteria	Exclusion criteria
a thin hypointense line or dot	the lesion has a diameter < 3 mm in any plane
can be visualized in at least two mutually perpendicular MR planes and appears as a thin line in at least one plane	The lesion blends with another lesion (blended lesion)
the vein has a small diameter (< 2 mm)	the lesion contains multiple distinct veins
It partially or completely traverses the lesion—the vein is centrally located within the lesion (i.e., it is approximately equidistant from the edges of the lesion and crosses the edge at no more than two points), regardless of the lesion’s shape	the lesion is poorly visible (due to motion or other MR-related artifacts)

 

 

Table 3. Definition of a lesion with a paramagnetic border [39].

Criteria	Exclusion criteria
a discrete rim with paramagnetic properties that is continuous around at least 2/3 of the outer edge of the white matter portion of the lesion (excluding any cortical or ependymal margins) on the slice with maximum visibility	veins running along the border that may resemble a rim
The border corresponds to the border of the entire lesion core or a portion thereof that is hyperintense on T2-weighted imaging	Warning signs and cautions small paramagnetic or diamagnetic structures, e.g., iron-containing ferritin or hemosiderin dots, venules, and myelin remnants lesions exhibiting magnetic dipole artifacts (often best visible on coronal or sagittal sections) anatomical regions with susceptibility artifacts (anterior temporal lobe, orbitofrontal cortex, and infratentorial regions)
the margin (or part of it) is discernible on at least 2 consecutive
the core of the lesion corresponds to the entire T2 hyperintense lesion or a part of it that does not enlarge on T1-weighted imaging after contrast administration

 

 

Table 4. McDonald Criteria 2024 –⁠ diagnostic pathway for establishing a diagnosis of MS [1].

Meets the 2017 McDonald criteria*
Typical clinical symptoms	+	4 out of 5 areas
	+	1 out of 5 areas	+	CVS or PRL	+	CSF or DIT
Asymptomatic patient/atypical symptoms		2 out of 5 areas	+	CSF or CVS or DIT

* cannot be determined based solely on the clinical picture; to meet the criterion of spatial dissemination, findings must be present in 2 out of 5 regions (plus the optic nerve, which can be assessed using magnetic resonance imaging, visual evoked potentials, or optical coherence tomography); in primary progressive MS, 2 spinal lesions satisfy the criterion of spatial dissemination

CSF –⁠ presence of intrathecal synthesis of oligoclonal bands or an elevated kappa light chain index; CVS –⁠ central venule sign in at least 6 lesions, or in the majority of lesions if their total number is < 10; DIT –⁠ dissemination in time, PRL –⁠ paramagnetic rim of the lesion (at least 1 lesion with a hypointense border at the edge of the lesion on susceptibility-weighted sequences)