DESCRIPTION

• Inflammation of the optic nerve (cranial nerve II) causing an optic neuropathy
• Commonly presents as acute demyelinating optic neuritis associated with multiple sclerosis (MS) (presenting complaint in 25% of MS patients), but other causes include infectious disease and systemic autoimmune disorders.
• Optic disc often normal in appearance at onset (retrobulbar ON, 67%) or swollen (papillitis, 33%).
• Key features:
  • Abrupt central visual loss (typically monocular)
  • Periorbital pain with eye movement (90%)
  • Dyschromatopsia: color vision deficits
  • Relative afferent pupillary defect (RAPD)
• Usually unilateral in adults; bilateral disease more common in children
• In children, headaches are common.
• System(s) affected: nervous
• Synonym(s): papillitis, demyelinating optic neuropathy; retrobulbar ON

EPIDEMIOLOGY

ETIOLOGY AND PATHOPHYSIOLOGY

• Cause is presumed to be a demyelinating autoimmune reaction.
• Neuromyelitis optica (NMO) IgG autoantibody, which targets the water channel aquaporin-4 (AQP4) in neuromyelitis optica spectrum disorder (NMOSD)
• Myelin oligodendrocyte glycoprotein (MOG) autoantibody in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD)
• Viral infections: measles, mumps, varicella-zoster, coxsackievirus, adenovirus, hepatitis A and B, HIV, herpes simplex virus, cytomegalovirus, SARS-CoV-2 (MOGAD can be seen with COVID-19) (1)
• Nonviral infections: syphilis, tuberculosis, meningococcus, cryptococcosis, cysticercosis, bacterial sinusitis, Streptococcus B, Bartonella, typhoid fever, Lyme disease
• Systemic inflammatory disease: sarcoidosis, systemic lupus erythematosus, vasculitis
• Local inflammatory disease: intraocular or contiguous with the orbit, sinus, or meninges

COMMONLY ASSOCIATED CONDITIONS

• MS (common): ON is associated with an increased risk of MS (30% risk in Optic Neuritis Treatment Trial [2])
• Other demyelinating diseases: NMO (Devic disease), multifocal demyelinating neuropathy, acute disseminated encephalomyelitis (ADEM)