Diagnostic Evolution of Multiple Sclerosis

Multiple sclerosis (MS) remains a complex autoimmune challenge for the central nervous system. Traditionally, diagnosis relied on demonstrating dissemination in space (DIS) across four specific anatomical regions. However, the recent 2024 McDonald criteria revision introduces a transformative shift by officially recognizing the optic nerve as a fifth topographic location. This update significantly increases diagnostic sensitivity, particularly for patients presenting with early symptoms. Clinicians can now use evidence of optic nerve involvement to fulfill DIS requirements more efficiently.

Practical Application of the 2024 McDonald Criteria

The inclusion of the optic nerve allows specialists to identify both clinical and subclinical demyelinating lesions using multimodal testing. For instance, magnetic resonance imaging (MRI) of the orbit can reveal classic inflammatory lesions. Furthermore, optical coherence tomography (OCT) provides objective structural data. Specifically, a peripapillary retinal nerve fiber layer (pRNFL) inter-eye difference of ≥6 µm suggests pathological thinning. Functional tests like visual evoked potentials (VEP) also play a crucial role by detecting delayed P100 latencies, indicating subclinical demyelination. Consequently, these tools empower neurologists to initiate disease-modifying therapies sooner, which improves long-term patient outcomes.

Differential Diagnosis and Clinical Frameworks

While the new criteria streamline MS diagnosis, practitioners must still exclude mimics. The framework proposed by Petzold et al. in 2022 helps distinguish MS-related optic neuritis from other etiologies. For example, clinicians must differentiate MS from neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD). These conditions often present with more severe visual loss or bilateral involvement. Therefore, using serological biomarkers like AQP4-IgG and MOG-IgG remains essential for diagnostic accuracy. Ultimately, the 2024 McDonald criteria represent a biology-driven approach that reflects the true clinical reality of MS.

Frequently Asked Questions

How does the 2024 McDonald criteria change MS diagnosis?

The criteria now include the optic nerve as a fifth anatomical site for dissemination in space (DIS). This change allows clinicians to diagnose MS earlier if they find lesions in at least two out of five specified CNS regions.

Which tests confirm optic nerve involvement in MS?

Clinicians use orbital MRI to find physical lesions, OCT to measure retinal thickness asymmetry, and VEP to identify functional conduction delays in the visual pathways.

Is optic nerve involvement mandatory for an MS diagnosis?

No, the optic nerve is one of five potential locations. A diagnosis requires lesions in at least two of the five regions, meaning MS can still be diagnosed without optic nerve involvement if other sites show characteristic lesions.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Gębka-Kępińska B et al. Optic nerve pathologies in multiple sclerosis based on the new McDonald criteria 2024. Neurol Neurochir Pol. 2026 Apr 01. doi: 10.5603/pjnns.109311. PMID: 41919454.

Montalban X et al. 2024 Revision of the McDonald diagnostic criteria for multiple sclerosis. Lancet Neurol. 2025;24(10):850-865.

Petzold A et al. Diagnosis and classification of optic neuritis. Lancet Neurol. 2022;21(12):1120-1134.