Optic Neuritis

The optic nerve becomes inflamed, resulting in optic neuritis. Eye pain and partial or total vision loss are the most common unilateral symptoms. Diagnosis is mainly clinical. Therapy is directed at the underlying disease; most cases resolve spontaneously.

Causes of Optic Neuritis

Optic neuritis is particularly common among adults aged 20 to 40. Most cases result from a demyelinating disease, particularly from multiple sclerosis, where relapses can occur. Optic neuritis is often the initial symptom of multiple sclerosis. Other causes include:

● Infectious diseases (e.g. viral encephalitis [particularly in children], sinusitis, meningitis, tuberculosis, syphilis, HIV)
● Neoplastic metastases along the optic nerve fibers
● Chemicals and pharmaceuticals (e.g. lead, methanol, quinine, arsenic, ethambutol, antibiotics)
● Optic neuromyelitis (1)
● Diseases associated with autoantibodies to myelinated oligodendrocyte glycoprotein and immunoglobulin G (2)

Diabetes, pernicious anemia, systemic autoimmune disorders, Graves’ ophthalmopathy, bee stings, and trauma are all rare causes. Often, the cause remains unknown despite a thorough evaluation.

Symptoms

The most common symptom of optic neuritis is vision loss, ranging from a tiny central or paracentral scotoma to full blindness and can happen in as little as one or two days. Most patients have mild eye pain that often intensifies with eye movement.

If the optic disc is edematous, the condition is called papillitis. If the optic disc appears normal, this condition is called retrobulbar neuritis. The most characteristic findings include reduced visual acuity, visual field deficit, color vision disturbances (often disproportionate to the loss of visual acuity). When the contralateral eye is intact or only slightly affected, an afferent pupillary defect is usually visible. The color vision test is a useful complement, although 10% of males have congenital color blindness, producing false-positive results. In more than two-thirds of patients, inflammation occurs in the retrobulbar region without causing visible changes on the optic nerve head. In the remaining cases, there are hyperemic disc, edema in or around the disc, vascular stasis, or a combination of these. There may be some exudates and hemorrhages near or corresponding to the optic disc.

Diagnosis

● Clinical evaluation
● Magnetic resonance (MRI)

Optic neuritis should be suspected in people who have characteristic pain associated with vision loss, especially if they are young. A neuroimaging study, preferably with a gadolinium-enhanced brain MRI, is routinely performed and may show an enlarged optic nerve. MRI can also help diagnose multiple sclerosis, the disease associated with autoantibodies to myelinated oligodendrocyte glycoprotein and immunoglobulin G, and neuromyelitis optica. Brain MRI, studied in fluid attenuating inversion recovery (FLAIR) sequences, may show typical demyelinating lesions in a periventricular site if optic neuritis is related to demyelination.

Prognosis

Prognosis depends on the underlying condition. Most episodes resolve spontaneously, with vision returning in 2-3 months. The majority of patients with a typical history of optic neuritis who have no underlying systemic disease, such as connective tissue disease, regain their vision. In contrast, about 25% of people have a recurrence in the same or opposite eye. Brain MRI is used to determine the future risk of demyelinating disease.

Tips and mistakes to avoid

Consider contrast (gadolinium) MRI in young patients who experience eye pain with movement and loss of vision (e.g. decreased visual acuity or color vision, field defects) or afferent pupillary defect.

Consider imaging of the spinal cord in patients with neurological symptoms suggestive of spinal cord involvement, which can be seen in both monomer disease and disease associated with myelinated oligodendrocyte glycoprotein autoantibodies and immunoglobulins G (NMO or MOG-IgG disease).

Treatment

● Corticosteroids

If multiple sclerosis or optic neuromyelitis is suspected, corticosteroids may be used. Treatment with methylprednisolone (500-1000 mg IV once / day) for 3 days followed by prednisone (1 mg/kg orally once / day) for 11 days may accelerate recovery, but final results concerning vision are no different from those of observation alone. In addition, IV corticosteroids have been reported to delay the onset of multiple sclerosis for at least 2 years. Treatment with oral prednisone alone does not improve vision outcomes and may increase the rate of relapse. Small tricks (e.g. use of magnifying glasses, large print, talking clocks) may be helpful to the patient. Other treatments, such as those used to treat multiple sclerosis, can be undertaken if there is a suspicion of multiple sclerosis.

Key points

● Optic neuritis is particularly common among adults aged 20 to 40.
● The most common causes are demyelinating diseases, particularly multiple sclerosis, neuromyelitis optica, and myelin oligodendrocyte glycoprotein (MOG-IgG) autoantibody disease, but infections, tumors, drugs, and toxins represent other possible causes (1).
● Mild pain with eye movement, visual abnormalities (especially disproportionate loss of color vision), and an afferent pupillary deficiency are all part of the judgement.
● Consider doing gadolinium MRI.
● Corticosteroids and other drugs may be given, especially if multiple sclerosis is suspected.

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