What is the treatment for a patient with MOG (Myelin Oligodendrocyte Glycoprotein) positive optic neuritis with no changes on MRI (Magnetic Resonance Imaging)?

Treatment of MOG-Positive Optic Neuritis with No Changes on MRI

For MOG-positive optic neuritis without MRI changes, first-line treatment is high-dose intravenous methylprednisolone (1g/day for 3-5 days) followed by oral prednisone taper over at least 4-6 weeks to prevent early relapse. 1, 2

Diagnosis Confirmation

Before initiating treatment, confirm the diagnosis with:

• Cell-based assays for MOG-IgG antibodies (current gold standard)
  • Must use full-length human MOG as target antigen
  • Use Fc-specific secondary antibodies to avoid cross-reactivity 1
• Serum is the preferred specimen for testing (over CSF) 1
• Clinical presentation typically includes:
  • Bilateral optic nerve involvement
  • Optic disc swelling
  • Severe vision loss
  • Pain with eye movement 2, 3

Acute Treatment Protocol

1. Initial Treatment:

   • IV methylprednisolone 1g/day for 3-5 days 1, 2
   • Begin immediately upon diagnosis, as delaying treatment may cause irreversible damage to the optic nerve 4

2. Oral Steroid Taper:

   • Follow with oral prednisone 1mg/kg/day
   • Taper slowly over at least 4-6 weeks 1, 2
   • Rapid tapering is associated with increased relapse risk 3

3. For Inadequate Response:

   • If no improvement or worsening after 3 days of IV steroids:
     • Consider plasma exchange (PLEX) or
     • Intravenous immunoglobulin (IVIG) 2g/kg over 5 days (0.4g/kg/day) 1

Relapse Prevention

For patients with relapsing disease:

1. First-line Maintenance Therapy:

   • Rituximab has shown effectiveness in stabilizing MOG-positive optic neuritis 1, 5

2. Alternative Maintenance Options:

   • Mycophenolate mofetil 4, 5
   • Azathioprine 5
   • Monthly IVIG 5

Monitoring and Follow-up

• Regular ophthalmological examinations to monitor visual acuity
• Optical coherence tomography (OCT) to assess:
  • Acute: optic nerve swelling
  • Chronic: optic nerve atrophy 3
• Visual evoked potentials to detect bilateral optic nerve damage 2

Important Considerations

• MOG-positive optic neuritis is distinct from MS and NMOSD and requires different management 1, 5
• Traditional MS treatments like interferon-beta may worsen MOG-associated disease 1
• Despite severe initial vision loss, MOG-positive optic neuritis typically has better recovery than AQP4-positive optic neuritis 5
• Multiple relapses are common in MOG-positive optic neuritis, necessitating close monitoring 6
• The absence of MRI changes does not exclude MOG-positive optic neuritis, as not all patients show radiological evidence 6, 3

Treatment Pitfalls to Avoid

1. Delayed Treatment: Initiate steroids promptly as delays may lead to irreversible optic nerve damage 4
2. Rapid Steroid Tapering: Avoid rapid tapering which increases relapse risk 3
3. Misdiagnosis as MS: MOG-positive optic neuritis requires different treatment than MS; MS therapies may worsen outcomes 1
4. Inadequate Follow-up: Regular monitoring is essential due to high relapse rates 6
5. Relying solely on MRI: Normal MRI findings do not exclude MOG-positive optic neuritis 6, 3