MOG Optic Neuritis in Children: Diagnosis and Treatment
Diagnosis
MOG-antibody testing should be performed in all children presenting with optic neuritis, as MOG-associated disease is significantly more common in pediatric populations (up to 70% of acquired demyelinating disease in young children) compared to adults, and the diagnostic threshold for testing should be less rigorous than in adults. 1
Clinical Presentation
Children with MOG optic neuritis typically present with:
- Bilateral involvement in 80% of cases, particularly in younger children (<10 years), with severe visual loss (52% presenting with visual acuity ≤ count fingers) 2, 3
- Eye pain in 88% of cases, accentuated by eye movements 2
- Prominent papilledema/papillitis/optic disc swelling during acute episodes, which is a key clinical indicator for MOG-IgG testing 1, 2
- Abnormalities in color perception and contrast sensitivity 2
Diagnostic Testing Algorithm
Test MOG-IgG and AQP4-IgG in parallel if cost permits; if cost is a factor, test AQP4-IgG first only if disease is stable. 1 However, given the high prevalence of MOG-associated disease in children, parallel testing is strongly preferred. 1
Critical Testing Requirements:
- Use only cell-based assays for MOG-IgG testing - ELISA has poor specificity and should not be used 4
- Serum MOG-antibody testing is the definitive diagnostic test 5, 6
- CSF analysis may show neutrophilic pleocytosis or WCC >50/μl (distinguishes from MS) 1
- Oligoclonal bands are typically absent (87-88% of MOG-EM patients lack OCBs) 1, 7
Neuroimaging Characteristics
MRI of orbits and head with and without contrast is the primary imaging modality. 1, 4
Key MOG optic neuritis imaging features include:
- Longitudinally extensive optic nerve lesions with median length of 23.1 mm (compared to 9.9 mm in MS) 1, 4
- Perioptic gadolinium enhancement during acute phase (highly specific for MOG-ON) 1, 4
- Involvement of >6/12 optic nerve segments or ≥4/5 segments (anterior intraorbital, posterior intraorbital, canalicular, intracranial, chiasmal) 1
- Normal supratentorial brain MRI or absence of MS-typical lesions (no Dawson's fingers, absent in 98.6% of pediatric MOG patients; no juxtacortical U-fiber lesions, absent in 94.2%) 1
- Bilateral optic nerve involvement is common 1
Important pitfall: Normal brain MRI does not exclude MOG optic neuritis and actually increases pre-test probability. 4
Treatment
Acute Phase Treatment
Administer intravenous methylprednisolone (IVMP) 4-30 mg/kg/day for 3-5 days as first-line acute treatment. 8, 6 This is standard of care despite the self-limited nature of some cases, given the severity of bilateral vision loss in children. 8
- 96% of MOG-positive patients receive corticosteroid treatment in acute phase 2
- Patients typically respond well to IVMP during acute attacks 6
- 16% may require plasma exchange if inadequate response to steroids 2
Oral Steroid Taper
Follow IVMP with a prolonged oral corticosteroid taper over 2-4 weeks (not days). 8 This extended taper is critical in pediatric populations.
Critical pitfall: Rapid steroid taper causes relapses in MOG optic neuritis - this is a common and preventable error. 4, 8
Long-term Management
Maintenance immunotherapy should be considered for children with recurrent MOG optic neuritis (36% of patients in one series received maintenance therapy). 2, 5
- Recurrent phenotype is common in MOG-associated disease 5, 6
- Multiple relapses of optic neuritis are typical in MOG patients 6
- MOG-positive disease has better prognosis than MS or AQP4-positive NMOSD, except in the recurrent subset 5
Visual Prognosis
Despite severe initial presentation, visual recovery is excellent in the majority of children, with 84% achieving 10-12/10 visual acuity after 6 months. 2 However, functional and structural studies show evidence of irreversible injury despite good high-contrast visual acuity recovery. 3
Aggressive acute treatment and relapse prevention favor good visual prognosis. 6