General
- Definition
- An inflammatory demyelinating process affecting the optic nerve
- Pathogenesis
- Inflammatory demyelination of the optic nerve there is perivascular cuffing, myelinating nerve sheath swelling, and myelin breakdown believed to be immune mediated
- Nomenclature
- ON is a feature of NMO and MS (more common)
- NMO is a multifocal, inflammatory demyelinating disorder of the central nervous system that preferentially affects the optic nerves and spinal cord.
- While most MS patients recover significant visual acuity following ON, NMO patients often manifest severe visual loss
Aetiology
- Multiple sclerosis
- Ethambutol
- Discontinue if findings
- Ischemic optic neuropathy
- (e.g., diabetes mellitus or giant cell arteritis)
- Considered in the elderly
- Infectious and postinfectious causes
- Considered in young children
- Sarcoid-associated optic neuropathy
- Lupus-associated optic neuropathy
- Lyme disease
- Syphilis
- Varicella
Presentation
- Symptoms
- Typically monocular but can occur in both eyes
- Vision loss typically occurs over the course of hours to days
- Most patients have a decrease in central visual acuity visual acuity decreases have different ranges
- Periocular pain often worsens with movement
- Physical exam
- Decreased visual acuity, colour sensitivity, and contrast sensitivity
- Fundoscopy optic disc pallor and/or optic disc swelling
- Relative afferent pupillary defect detected by the swinging light test
- In the affected eye, the pupil will dilate with direct illumination after illuminating the normal eye
Investigation
- Gadolinium-enhanced MRI of the orbit and brain
- Antinuclear antibody (ANA) if an autoimmune process is suspected
Management
- High-dose IV corticosteroids
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