Chronic relapsing inflammatory optic neuropathy
A steroid-dependent optic neuritis with relapsing visual loss.
Chronic relapsing inflammatory optic neuropathy, or CRION, is a recurrent optic neuritis that responds to and depends on steroids. Patients often feel pain with vision loss. Diagnosis requires excluding other causes, as a 2017 antibody test reclassified many cases as MOG antibody disease. Early detection is vital to prevent severe vision loss, as treatment with steroids or B-cell therapy works. Relapses typically follow steroid reduction or cessation.
Quick Facts
- Field
- Ophthalmology
- Neurology
- Neuro-ophthalmology
- Diagnosis
- Consensus Diagnostic Criteria
- Differential
- Optic neuritis subgroups
- Treatment
- Corticosteroids
Facts from the source article.
Signs and symptoms
Ocular pain and visual loss are typical, though painless cases occur. Bilateral severe visual loss (simultaneous or sequential) is common, but unilateral loss has been reported. A relative afferent pupillary defect may be present. At least one relapse occurs, with up to 18 relapses documented in an individual. Intervals between episodes range from days to over a decade. Symptoms improve with corticosteroids, and recurrence characteristically follows dose reduction or cessation.
Pathogenesis
In 2013 the etiology was unknown, though an immune-mediated basis was presumed due to treatment response. By 2015 research linked CRION to MOG antibody-associated encephalomyelitis. As of 2019, the correlation is so high that CRION is considered the most common phenotype related to myelin oligodendrocyte glycoprotein antibodies (MOG-IgG). As of 2021, some reports describe a second kind of CRION due to anti-phospholipid antibodies.
Diagnosis
CRION is a clinical diagnosis of exclusion. Any cause of optic neuropathy must be ruled out, including demyelinating conditions (MOG antibody disease, multiple sclerosis, neuromyelitis optica), systemic diseases (diabetic, toxic, nutritional, infectious), sarcoidosis, systemic lupus erythematosus, other autoimmune disease, and hereditary causes such as Leber's hereditary optic neuropathy. In 2014 no diagnostic biomarkers or typical imaging features existed. Testing for antinuclear antibodies (ANA), B12, folate, thyroid function, anti-aquaporin-4 antibodies (NMO-IgG), and glial fibrillary acidic protein (GFAP) helps exclude other diseases. Most patients are seronegative for NMO-IgG and GFAP. ANA is generally negative. CSF lacks oligoclonal bands typical of multiple sclerosis. Chest imaging is ordered if sarcoidosis is suspected. MRI may show optic nerve inflammation but not in all patients; diffusion tensor imaging can detect white matter abnormalities in those with normal MRI. Five diagnostic criteria were proposed in 2014: history of optic neuritis with one relapse, objectively measured visual loss, NMO-IgG seronegative, contrast enhancement on imaging of acutely inflamed optic nerves, and response to immunosuppressive treatment with relapse on withdrawal or dose reduction. CRION was included as a subtype in a 2022 international consensus classification of optic neuritis.
Treatment
Treatment has three phases. Acute phase: IV methylprednisolone 1 mg/kg for 3–5 days or plasmapheresis to restore visual function. Intermediate phase: oral prednisone 1 mg/kg with taper to stabilize vision. Long-term phase: transition to a steroid-sparing agent such as B-cell depleting therapy, azathioprine, methotrexate, cyclophosphamide, mycophenolate, IVIG, plasma exchange, cyclosporine, or infliximab. Corticosteroids induce prompt relief of pain and improved vision; complete restoration is possible, though exact success rates are unknown.
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