Definition and epidemiology
Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disorder of the central nervous system characterised by inflammatory lesions disseminated in space and time. Approximately 3–5% of all MS cases have onset before 18 years (pediatric-onset MS, POMS); onset before 10 years is rare. The overwhelming majority of children (>95%) present with a relapsing-remitting course, and relapse frequency is often higher than in adults, although disability accrues more slowly. There is a female predominance after puberty; pre-pubertal sex ratios are closer to equal. Risk associations mirror adult MS — low vitamin D, prior Epstein-Barr virus infection, obesity, and HLA-DRB1*15:01.
Clinical features
Children most often present with a clinically isolated syndrome — a first acute or subacute demyelinating event such as:
- Optic neuritis — painful monocular visual loss, dyschromatopsia
- Brainstem/cerebellar syndromes — diplopia, internuclear ophthalmoplegia, ataxia, vertigo
- Partial myelitis — sensory level, limb weakness, bladder symptoms
- Hemispheric/sensory syndromes
Younger children more often have polysymptomatic presentations and, occasionally, encephalopathy that can blur the line with acute disseminated encephalomyelitis (ADEM). Cognitive involvement and fatigue are under-recognised and important for schooling.
Diagnosis
Diagnosis rests on demonstrating dissemination in space (DIS) and time (DIT) while excluding better explanations. The 2017 McDonald criteria are validated in children older than ~11 years with a non-ADEM presentation, in whom they enable earlier diagnosis; applied at the first event they gain sensitivity at some cost to specificity versus the 2010 criteria (~83% sensitivity, ~73% specificity; Hacohen 2019). Key 2017 features applicable to children:
- CSF oligoclonal bands can substitute for DIT
- Symptomatic lesions may count toward DIS and DIT
- Cortical lesions combine with juxtacortical lesions for DIS
MRI (brain and cord) with gadolinium is the cornerstone; CSF for oligoclonal bands/IgG index supports the diagnosis. MOG-IgG and AQP4-IgG serology are essential — a positive result reclassifies the child as MOG-antibody disease or NMOSD, not MS, and changes treatment entirely. In children under ~11 or after an ADEM-like first event, McDonald criteria perform poorly; a second non-encephalopathic clinical event is generally required.
See the full criteria: Multiple Sclerosis (McDonald Criteria)
Red flags (suggesting an MS mimic)
- Encephalopathy, especially in a young child — consider ADEM/MOGAD
- Bilateral simultaneous optic neuritis or longitudinally extensive myelitis — consider MOGAD/NMOSD (test antibodies)
- Fever, meningism, raised inflammatory markers, marked CSF pleocytosis (>50 cells)
- Progressive rather than relapsing course from onset, or a normal brain MRI
- Metabolic/genetic leukodystrophy features (symmetric, progressive, family history)
Management overview
Acute relapses are treated with high-dose corticosteroids; plasma exchange or IVIG are options for steroid-refractory severe attacks. Disease-modifying therapy (DMT) is started early to reduce relapses and lesion accrual; several agents now carry pediatric indications, and higher-efficacy therapies are increasingly used up-front given the high relapse rate in children. DMT selection, monitoring, and pregnancy/adolescent counselling belong with a pediatric neurologist/MS service. Comprehensive care includes vitamin D optimisation, vaccination review before immunosuppression, fatigue and mood screening, cognitive/educational support, and MRI surveillance. Confirmation of MS over MOGAD/NMOSD must precede DMT choice, as MS therapies can worsen those conditions.
References
- Thompson AJ, et al. 2017 revisions of the McDonald criteria. Lancet Neurol. 2018;17:162–173.
- Hacohen Y, et al. Real-world validation of the 2017 McDonald criteria for pediatric MS. Neurol Neuroimmunol Neuroinflamm. 2019;6:e528.
- Krupp LB, et al. IPMSSG revised consensus definitions. Mult Scler. 2013;19:1261–1267.
Decision support for qualified clinicians only — verify against current primary guidelines and your clinical judgement.