How should a patient with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) and negative MRI findings be managed?

Management of MOGAD with Negative MRI Scans

In MOGAD patients with negative MRI findings, the diagnosis should still be pursued based on clinical phenotype and positive MOG-IgG serology using cell-based assays, and treatment should proceed with high-dose intravenous corticosteroids followed by careful tapering, as MRI-negative MOGAD is a recognized entity that requires the same aggressive immunotherapy as MRI-positive cases.

Diagnostic Approach

Confirm the Diagnosis Despite Negative Imaging

MOGAD can present with clinically evident demyelination even when MRI appears normal 1, 2. The diagnosis requires three components 3:

• Monophasic or relapsing acute optic neuritis, myelitis, brainstem encephalitis, or encephalitis
• MRI or electrophysiological findings compatible with CNS demyelination (visual evoked potentials can substitute for MRI in isolated optic neuritis)
• Seropositivity for MOG-IgG detected by cell-based assay using full-length human MOG

Critical Testing Considerations

When MRI is negative but clinical suspicion remains high:

• Repeat MOG-IgG testing during acute attacks if initially negative, as antibody concentrations are higher during active disease 3
• Use a second methodologically different cell-based assay to confirm positive results 3
• Test serum, not CSF - MOG-IgG is produced extrathecally and serum is the specimen of choice 3
• Consider timing issues: MOG-IgG may be transiently negative after plasma exchange or IVIG; retest 1-3 months later if these treatments were given 3

Electrophysiological Support

In patients with isolated optic neuritis and normal MRI, visual evoked potentials showing demyelination patterns can fulfill the requirement for objective evidence of CNS demyelination 3.

Acute Treatment Protocol

First-Line Therapy

Initiate high-dose intravenous methylprednisolone immediately upon clinical suspicion, without waiting for antibody results 4:

• 1 gram IV daily for 5 days
• Followed by slow oral steroid taper (not abrupt cessation, which increases relapse risk significantly - hazard ratio 4.68) 3
• Monitor closely for steroid-dependent flare-ups, which are common in MOGAD 3

Escalation for Incomplete Recovery

If response to steroids is inadequate:

• Plasma exchange or immunoadsorption - MOGAD patients show particularly good responses to antibody-depleting therapies 3
• IVIG - especially effective in pediatric cases 3

Long-Term Management Considerations

Monitoring Strategy

• Retest MOG-IgG at 6-12 months after initial attack 3
  • Persistent seropositivity suggests relapsing course
  • Antibody disappearance may indicate monophasic disease (though this is more common in pediatric ADEM)
  • Transient seronegativity can occur with immunosuppression; confirm with repeat testing before discontinuing treatment 3

Maintenance Immunotherapy

For relapsing disease or incomplete recovery from first attack 5:

• B-cell depleting therapies (rituximab) - particularly effective in MOGAD 3
• Chronic immunosuppression options: azathioprine, mycophenolate, cyclophosphamide
• IVIG as alternative maintenance option

Key Clinical Pitfalls

Do Not Dismiss the Diagnosis Based on Normal MRI

Multiple case reports confirm MRI-negative myelitis 1, 2 and encephalitis 6 in confirmed MOGAD. Clinical phenotype plus positive MOG-IgG is sufficient for diagnosis 3.

Recognize High-Risk Clinical Features

Even without MRI lesions, suspect MOGAD when you see:

• Bilateral or recurrent optic neuritis 3
• Severe visual deficit or blindness 3
• Myelitis with sphincter/erectile dysfunction 3
• Steroid-dependent symptoms or frequent flare-ups after steroid taper 3
• Acute encephalopathy with seizures 4

Avoid Treatment Delays

Do not wait for antibody results to initiate corticosteroids - laboratory processing can take 10+ days while clinical deterioration progresses 4. Treat based on clinical and available radiological suspicion.

Beware False-Negative Antibody Testing

MOG-IgG testing can be falsely negative if:

• Tested during remission rather than acute attack 3
• Patient on immunosuppression 3
• Recent plasma exchange or IVIG (retest 1-3 months later) 3
• Low-sensitivity assay used (ensure cell-based assay with full-length human MOG) 3

Special Populations

In elderly patients presenting with encephalitis and negative imaging, maintain high suspicion for MOGAD despite atypical demographics 6. In pediatric cases, the threshold for MOG-IgG testing should be lower as prevalence is much higher (up to 70% in young children with demyelinating disease) 3.