TABLE 3–3.

MRI Findings in Optic Neuritis

Diagnosis	Optic Nerve Imaging	Orbital Imaging	Brain and Spinal Cord Imaging
Multiple sclerosis	Unilateral, retrobulbar and canalicular, short anterior segmental lesions, optic nerve enhancement	Negative	Periventricular ovoid lesions, subcortical and juxtacortical lesions
Neuromyelitis optica (NMO) spectrum disorder	May be bilateral, often intracranial involving chiasm and optic tract, often longitudinally extensive, optic nerve enhancement	Negative	Longitudinally extensive transverse myelitis, posterior fossa and periaqueductal gray lesions, hypothalamic lesions
MOG-IgG	Frequently bilateral and retrobulbar, often longitudinally extensive, optic nerve and perineural sheath enhancement	Enhancement of perineural orbital tissue	Myelitis (thoracolumbar and conus predominance), lesions of deep gray nuclei
Seronegative (AON, RION, CRION)	Retrobulbar, optic nerve enhancement, occasional nerve swelling	Normal	Normal
Granulomatous (sarcoidosis, granulomatosis with polyangiitis)	Commonly unilateral, frequent combined optic nerve and sheath enhancement	Sarcoid: orbital apex inflammation Granulomatosis with polyangiitis: orbital cellulitis, orbital mass, orbital pseudotumor	Sarcoidosis: periventricular lesions, leptomeningeal lesions, pituitary and hypothalamic lesions Granulomatosis with polyangiitis: pachymeningitis, nonspecific gray and white matter lesions due to vasculitis
Autoimmune (Sjogren syndrome, systemic lupus erythematosus)	Retrobulbar, optic nerve enhancement	Normal	Systemic lupus erythematosus: infarcts and dural thrombosis
GFAP-IgG	Normal	Normal	Linear radial perivascular enhancement, meningitis, myelitis, leptomeningeal and ependymal enhancement
Paraneoplastic (CRMP-5)	Bilateral, optic nerve enhancement	Normal	Cerebellar atrophy, mesial temporal lesions, cerebellar lesions, myelitis (may be longitudinally extensive)
Neuroretinitis	Normal, occasional high T2 signal or enhancement in proximal optic nerve	Normal	Normal
Syphilis	Optic nerve and perineural sheath enhancement	Occasional enhancement of orbital fat	Leptomeningeal enhancement, encephalitis, myelitis, infarct
Lyme disease	Retrobulbar, optic nerve enhancement	Normal	Cranial nerve enhancement, periventricular and subcortical lesions
Tuberculosis	Retrobulbar, optic nerve and sheath enhancement	Orbital tuberculoma, dacryoadenitis	Leptomeningeal enhancement, ependymitis, tuberculoma
Viral infection	Retrobulbar, optic nerve enhancement	Normal	Variable depending on pathogen

AON = autoimmune optic neuropathy; CRION = chronic relapsing inflammatory optic neuropathy; CRMP-5 = collapsin response mediator protein-5; GFAP-IgG = glial fibrillary acidic protein immunoglobulin G; MOG-IgG = myelin oligodendrocyte glycoprotein immunoglobulin G; MRI = magnetic resonance imaging; RION = relapsing isolated optic neuritis.