What is the treatment for a patient with MOG (Myelin Oligodendrocyte Glycoprotein) positive status and bilateral ptosis?

Treatment of MOG-Positive Disease with Bilateral Ptosis

Initiate high-dose intravenous methylprednisolone at 1000 mg/day for 3-5 days immediately, as this is the first-line treatment for MOG encephalomyelitis presenting with brainstem involvement manifesting as bilateral ptosis. 1, 2

Acute Phase Management

Initial Treatment

• Start IV methylprednisolone 1000 mg/day for 3-5 days without delay, as treatment delays beyond 2 weeks are associated with significantly poorer outcomes 1, 2
• Bilateral ptosis in MOG-positive patients indicates brainstem encephalitis, which falls within the diagnostic criteria for MOG encephalomyelitis (monophasic or relapsing acute optic neuritis, myelitis, brainstem encephalitis, or encephalitis) 3
• Most MOG-positive patients (64%) present with moderate-severe symptoms but 74% demonstrate good response to initial steroid therapy 4

Second-Line Therapy for Steroid-Refractory Cases

• Proceed to plasma exchange (PLEX) if no improvement after 3-5 days of IV steroids, as this is effective in severe cases not responding to corticosteroids 1, 2, 5
• Consider rituximab for refractory cases, particularly if relapsing disease pattern emerges 1, 2

Long-Term Management Strategy

Relapse Prevention

• The cumulative relapse probability is 42.8% at 1 year and 62.8% at 4 years in MOG-positive disease, making maintenance immunosuppression critical 4
• Relapses occur in 50-60% of patients during corticosteroid dose reduction, necessitating maintenance therapy 1, 2
• Initiate long-term immunosuppression with rituximab or oral immunosuppressants (azathioprine, mycophenolate mofetil) after the acute phase, especially if this represents a second attack 1, 5

Monitoring and Prognostic Testing

• Retest MOG-IgG antibodies 6-12 months after the initial attack to assess prognosis, as antibody disappearance may indicate monophasic disease (though this is more common in pediatric ADEM cases) 3
• MOG-IgG remained detectable in all 18 patients with relapsing disease course at mean 33-month follow-up, suggesting persistent seropositivity predicts relapsing course 3
• Close monitoring is essential if discontinuing immunosuppression, as transient seronegativity can occur followed by later seroconversion 3

Critical Diagnostic Considerations

Confirming MOG-EM Diagnosis

• Ensure MOG-IgG was detected by cell-based assay using full-length human MOG as the target antigen, as this is the gold standard 3
• Obtain MRI of brain and spine to document demyelinating lesions compatible with brainstem encephalitis 3, 1
• Brainstem lesions in MOG-positive disease can be poorly demarcated and infratentorial, distinct from typical MS patterns 4

Excluding Alternative Diagnoses

• Rule out myasthenia gravis as a cause of bilateral ptosis, though this would not explain MOG seropositivity 6
• Consider co-existing NMDAR encephalitis if atypical features present (behavioral changes, seizures, altered consciousness), as rare co-occurrence has been reported; exclude teratoma in such cases 3
• Verify negative AQP4-IgG antibodies, as co-existence of MOG-EM and AQP4-NMOSD is extremely rare but must be assumed if both are positive 3

Common Pitfalls to Avoid

• Do not use interferon-beta or natalizumab, as these MS therapies can worsen MOG-positive disease and increase relapse rates 3, 1
• Do not taper steroids too rapidly, as symptom flare-ups frequently occur with steroid reduction; consider steroid-sparing agents early 3, 1
• Do not assume monophasic disease after a single attack, as the interval between first and second attacks can extend several years in some MOG-positive patients 3
• Recognize that CSF may show neutrophilic pleocytosis (present in 64.3% of MOG-EM patients with pleocytosis) and lack oligoclonal bands, which can mimic CNS infection 3