MOGAD: Diagnosis & Clinical Features
Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a distinct antibody-mediated CNS demyelinating disorder that differs from both multiple sclerosis (MS) and aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD) in pathophysiology, clinical features, treatment response, and prognosis. MOGAD was formally defined as a separate disease entity with the publication of the 2023 International MOGAD Panel diagnostic criteria, establishing standardized requirements for antibody testing, clinical phenotypes, and supporting features.
Bottom Line
- Pathophysiology: MOG-IgG causes reversible demyelination with preservation of astrocytes (unlike AQP4-NMOSD astrocytopathy); less efficient complement activation than AQP4-IgG
- Demographics: Equal sex ratio in adults (unlike MS and AQP4-NMOSD); bimodal age distribution with peaks in childhood and 30–50 years
- Core phenotypes: Optic neuritis (most common), myelitis, ADEM, brainstem syndrome, cerebral cortical encephalitis, and cerebral monofocal/polyfocal deficits
- Diagnosis: Requires MOG-IgG positivity by cell-based assay (CBA only — other assays not accepted) plus ≥1 core clinical manifestation; clear positivity vs. low-positive titers have different supporting requirements
- Disease course: ~50% monophasic, ~50% relapsing; generally better recovery than AQP4-NMOSD
- MRI features: Perineural optic sheath enhancement, longitudinal ON lesions, conus involvement, cortical lesions with meningeal enhancement, ill-defined brain lesions
Pathophysiology
MOG is a glycoprotein expressed exclusively on the outermost surface of myelin sheaths in the CNS, making it accessible to circulating antibodies. Key pathophysiologic features of MOGAD include:
- Reversible demyelination: Pathology shows demyelination with relative preservation of astrocytes and axons, in stark contrast to the astrocyte-destructive pathology of AQP4-NMOSD
- Less efficient complement activation: MOG-IgG activates complement less efficiently than AQP4-IgG, which may partly explain the generally better outcomes in MOGAD
- T-cell-mediated component: Perivenous pattern of demyelination with prominent inflammatory infiltrates suggests a combined antibody- and cell-mediated process
- Lesion resolution: MRI lesions in MOGAD frequently resolve or significantly decrease over time, reflecting the potentially reversible nature of the underlying pathology
Epidemiology
| Feature | MOGAD | AQP4-NMOSD | MS |
|---|---|---|---|
| Sex ratio (F:M) | ~1:1 (adults) | ~9:1 | ~3:1 |
| Peak age of onset | Bimodal: childhood & 30–50y | 30–50 years | 20–40 years |
| Pediatric prevalence | Common (especially ADEM) | Rare | ~5% of cases |
| Racial/ethnic predilection | All backgrounds | Non-White predominance | Northern European predominance |
Core Clinical Phenotypes
Optic Neuritis
Optic neuritis is the most common manifestation of MOGAD, with several distinguishing features compared to MS and AQP4-NMOSD:
- Bilateral simultaneous involvement is common (unusual in MS)
- Anterior optic nerve predilection with prominent optic disc edema (compared to posterior/chiasmal predilection in AQP4-NMOSD)
- Longitudinally extensive involvement — optic nerve lesions extending >50% of nerve length on MRI
- Perineural optic sheath enhancement on MRI — a highly characteristic finding
- Prodromal headache may precede visual symptoms
- Generally good visual recovery, though recurrent attacks can lead to cumulative visual loss
Myelitis
- Longitudinally extensive transverse myelitis (LETM) is common, as in AQP4-NMOSD
- Central cord/H-sign pattern on axial MRI (grey matter predominant)
- Conus medullaris involvement — relatively specific for MOGAD among CNS demyelinating diseases
- Generally better motor recovery than AQP4-NMOSD
- Lesions frequently resolve or significantly shrink on follow-up MRI
Acute Disseminated Encephalomyelitis (ADEM)
- Defined as acute polyfocal neurologic deficits with encephalopathy accompanied by multifocal T2 lesions on MRI
- Most common MOGAD presentation in children
- Ill-defined, large, often bilateral white matter lesions, frequently involving deep grey matter structures
- MOG-IgG is detected in approximately 30–50% of pediatric ADEM cases
Brainstem and Cerebellar Syndromes
- Ill-defined T2 hyperintensities involving the pons, middle cerebellar peduncle, or medulla
- Can present with cranial neuropathies, vertigo, ataxia, or diplopia
- Area postrema syndrome (intractable nausea/vomiting/hiccups) is less common than in AQP4-NMOSD but can occur
Cerebral Cortical Encephalitis
A relatively unique MOGAD phenotype characterized by:
- MRI evidence of FLAIR cortical hyperintensity often with enhancement of the overlying meninges
- Accompanied by cerebral irritability: encephalopathy, headache, focal deficits, and seizures
- Seizures are part of the diagnostic definition and are uncommon in MS and AQP4-NMOSD
- Can be confused with autoimmune encephalitis, infectious meningitis, or CNS vasculitis
Cerebral Monofocal or Polyfocal Deficits
- Similar to ADEM but without encephalopathy
- Multiple ill-defined T2 hyperintense lesions in supratentorial and often infratentorial white matter
- Deep grey matter involvement may be seen
MRI Features
| Location | MOGAD Features | Key Distinguishing Points |
|---|---|---|
| Optic nerve | Longitudinally extensive (>50% nerve length), perineural sheath enhancement, optic disc edema, bilateral | Anterior predilection (vs. posterior/chiasmal in AQP4-NMOSD); sheath enhancement is relatively specific |
| Spinal cord | LETM, central cord/H-sign, conus involvement, lesion resolution over time | Conus lesions favor MOGAD; lesions often resolve (unlike AQP4-NMOSD where atrophy develops) |
| Brain | Ill-defined T2 lesions, deep grey matter involvement, cortical lesions with leptomeningeal enhancement | Lesions do NOT resemble typical MS plaques; cortical involvement with meningeal enhancement is characteristic |
| Brainstem | Ill-defined T2 hyperintensity in pons, middle cerebellar peduncle, medulla | Distinguished from the pencil-thin ependymal enhancement of AQP4-NMOSD |
MRI Lesion Evolution in MOGAD
A hallmark of MOGAD is the tendency for MRI lesions to resolve or substantially decrease on follow-up imaging, which contrasts with both MS (where lesions persist and may develop as T1 black holes) and AQP4-NMOSD (where lesion resolution is accompanied by significant tissue atrophy). This MRI behavior reflects the relatively reversible, demyelinating pathology of MOGAD. Persistent or worsening lesions over time should prompt reconsideration of the diagnosis.
Diagnostic Criteria (2023 International MOGAD Panel)
The diagnosis of MOGAD requires fulfillment of three criteria (A, B, and C):
Criterion A: Core Clinical Manifestation
At least one of the following six core phenotypes:
- Acute or subacute optic neuritis
- Acute or subacute myelitis
- ADEM (acute polyfocal deficits with encephalopathy + multifocal MRI lesions)
- Cerebral monofocal or polyfocal deficits without encephalopathy
- Acute or subacute brainstem or cerebellar deficits
- Cerebral cortical encephalitis with seizures
Criterion B: MOG-IgG Positivity by Cell-Based Assay
Only cell-based assays are accepted for MOGAD diagnosis (unlike AQP4-NMOSD, where other assays can be used with caution). The criteria distinguish two levels of positivity:
| MOG-IgG Level | Definition | Additional Requirements |
|---|---|---|
| Clear positivity | ≥2 doubling dilutions above assay cutoff (live CBA) or titer ≥1:100 (fixed CBA) | No additional supporting features required |
| Low positivity | Low-range positivity (live CBA) or titer 1:10–1:100 (fixed CBA), OR unknown/not reported titer, OR isolated CSF positivity | Requires: (1) negative AQP4-IgG AND (2) ≥1 supporting clinical or MRI feature |
False Positivity Risk
- Low-positive MOG-IgG titers carry a significant risk of false positivity — hence the requirement for supporting features
- ELISA and other non-CBA assays are not accepted for MOGAD diagnosis due to unacceptable false-positive rates
- In borderline cases, repeat testing with a more accurate assay (e.g., live vs. fixed CBA) is advised
- Consultation with a demyelinating disease specialist is recommended when in doubt
Supporting Clinical and MRI Features
Required when MOG-IgG positivity is low or uncertain:
| Phenotype | Supporting Features |
|---|---|
| Optic neuritis | Bilateral simultaneous involvement; >50% nerve length on MRI; perineural optic sheath enhancement; optic disc edema |
| Myelitis | Longitudinally extensive spinal cord lesion; central cord/H-sign; conus lesion |
| Brain/brainstem syndrome | Multiple ill-defined T2 lesions in supra/infratentorial white matter; deep grey matter involvement; ill-defined pons/MCP/medulla lesions; cortical lesion with leptomeningeal enhancement |
Criterion C: Exclusion of Alternative Diagnoses
Common red flags that should prompt reconsideration include:
- Progressive disease course (primary or secondary progressive) — consider MS, sarcoidosis, metabolic or genetic etiologies
- Hyperacute onset (<4 hours) — consider stroke or ischemic etiologies
- Typical MS lesion morphology on brain MRI (ovoid periventricular, Dawson fingers, ring/open-ring enhancement)
- CSF-restricted oligoclonal bands — consider MS or sarcoidosis
- Development of new asymptomatic lesions over time — favors MS
- Lack of lesion resolution over time (uncommon in MOGAD)
- Lack of response to corticosteroids and PLEX
Disease Course and Prognosis
| Feature | Detail |
|---|---|
| Monophasic course | ~50% of patients; single attack with no recurrence |
| Relapsing course | ~50% of patients; predominantly optic neuritis relapses |
| Progressive course | Not a recognized feature of MOGAD; its presence should prompt reconsideration of diagnosis |
| Recovery | Generally better than AQP4-NMOSD; complete or near-complete recovery is common |
| MOG-IgG seroconversion | Conversion to seronegative status reduces future relapse risk; serial monitoring informative |
| Disability drivers | Visual impairment from recurrent ON; motor deficits from severe myelitis attacks |
CSF Findings in MOGAD
- CSF pleocytosis is common (often higher cell counts than MS)
- Oligoclonal bands are typically absent (<20% positive) — their presence should raise suspicion for MS
- Elevated protein is common during acute attacks
- Neutrophilic predominance may be seen acutely (unlike the lymphocytic predominance typical of MS)
Differentiation from MS and AQP4-NMOSD
| Feature | MOGAD | AQP4-NMOSD | MS |
|---|---|---|---|
| Antibody | MOG-IgG | AQP4-IgG | None specific |
| Pathology | Demyelination, astrocytes preserved | Astrocytopathy | Demyelination, axonal loss |
| OCBs | Usually absent | Usually absent | Present ~90% |
| ON pattern | Anterior, bilateral, sheath enhancement | Posterior/chiasmal | Retrobulbar, unilateral |
| Myelitis | LETM, conus, H-sign | LETM, bright spotty lesions | Short, peripheral lesions |
| Brain lesions | Ill-defined, cortical, resolve | Periependymal, cloud-like | Ovoid, periventricular, persistent |
| Course | 50% monophasic, no progression | >90% relapsing, no progression | Relapsing then progressive |
| Recovery | Generally good | Often poor | Variable |
References
- Sechi E. Neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease. Continuum (Minneap Minn). 2024;30(4):1057-1090.
- Banwell B, Bennett JL, Marignier R, et al. Diagnosis of myelin oligodendrocyte glycoprotein antibody-associated disease: International MOGAD Panel proposed criteria. Lancet Neurol. 2023;22(3):268-282.
- Sechi E, Cacciaguerra L, Chen JJ, et al. Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD): a review of clinical and MRI features, diagnosis, and management. Front Neurol. 2022;13:885218.
- Höftberger R, Guo Y, Flanagan EP. The pathology of central nervous system inflammatory demyelinating disease accompanying myelin oligodendrocyte glycoprotein autoantibody. Acta Neuropathol. 2020;139(5):875-892.
- Takai Y, Misu T, Kaneko K. Myelin oligodendrocyte glycoprotein antibody-associated disease: an immunopathological study. Brain. 2020;143(5):1431-1446.
- Valencia-Sanchez C, Guo Y, Krecke KN, et al. Cerebral cortical encephalitis in myelin oligodendrocyte glycoprotein antibody-associated disease. Ann Neurol. 2023;93(2):297-302.