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- Inflammation of the optic nerve (cranial nerve II)
- Most common form is acute demyelinating optic neuritis (ON), but other causes include infectious disease and systemic autoimmune disorders.
- Optic disc may be normal in appearance at onset (retrobulbar ON, 67%) or swollen (papillitis, 33%).
- Key features:
- Abrupt visual loss (typically monocular)
- Periorbital pain with eye movement (90%)
- Pain in the distribution of the first division of the trigeminal nerve
- Dyschromatopsia: color vision deficits
- Relative afferent pupillary defect (RAPD)
- Usually unilateral in adults; bilateral disease more common in children
- Presenting complaint in 25% of patients with multiple sclerosis (MS)
- In children, headaches are common.
- System(s) affected: nervous
- Synonym(s): papillitis, demyelinating optic neuropathy; retrobulbar ON
- 5/100,000 cases per year
- More common in northern latitudes
- More common in spring season
- More common in whites than in other races
- Predominant age: 18 to 45 years; mean age 30 years
- Predominant sex: female > male (3:1)
Etiology and Pathophysiology
- In both MS-associated and isolated monosymptomatic ON, the cause is presumed to be a demyelinating autoimmune reaction.
- Possible mechanisms of inflammation in immune-mediated ON are the cross-reaction of viral epitopes and host epitopes and the persistence of a virus in CNS glial cells.
- Neuromyelitis optica (NMO) IgG autoantibody, which targets the water channel aquaporin-4
- Primarily idiopathic
- Viral infections: measles, mumps, varicella-zoster, coxsackievirus, adenovirus, hepatitis A and B, HIV, herpes simplex virus, cytomegalovirus
- Nonviral infections: syphilis, tuberculosis, meningococcus, cryptococcosis, cysticercosis, bacterial sinusitis, streptococcus B, Bartonella, typhoid fever, Lyme disease, fungus
- Systemic inflammatory disease: sarcoidosis, systemic lupus erythematosus, vasculitis
- Local inflammatory disease: intraocular or contiguous with the orbit, sinus, or meninges
- Toxic: lead, methanol, arsenic, radiation
- Vascular lesions affecting the optic nerve
- Posterior uveitis (i.e., birdshot retinochoroidopathy, toxoplasmosis, toxocariasis)
- Medications: ethambutol, chloroquine, isoniazid, chronic high-dose chloramphenicol, tumor necrosis factor α-antagonist, infliximab (Remicade), adalimumab (Humira), etanercept (Enbrel)
Commonly Associated Conditions
- MS (common): ON is associated with an increased risk of MS.
- Other demyelinating diseases: Guillain-Barré syndrome, Devic NMO, multifocal demyelinating neuropathy, acute disseminated encephalomyelitis