Optic Neuritis

• Believed to be due to autoimmune reaction damaging the myelin sheath of optic nerve neurons
• Higher propensity in patients with autoimmune diseases
• Associated with HLA DRB1 and HLA-B27Potentially triggered by viral illnesses
• Usually monocular visual loss
• Associated with MS
• Risk factors:
  • Age (20-40 years)
  • female sex (2:1)
  • Caucasian race

Clinical

• Acute onset of monocular eye pain and vision loss,
• pain with eye movements
• previous similar events
• Develops rapidly – peaks within 1-2 weeks
• RAPD
• Disc may be normal or blurred/swollen
• Flickering or flashes of light
• Loss of colour vision

Treatment / Management:

• Visual recovery usually occurs over weeks to months
• Corticosteroid therapy hastens recovery:
  • IV methylprednisolone (500-1000mg daily for 3 days)
  • Oral prednisone (1mg/kg daily for 11 days)
• Immune-modulating therapies for MS-related lesions

Differential Diagnosis

The differential diagnosis of optic neuritis includes the following conditions:

• Inflammatory, demyelinating disease (classic)
  • Idiopathic optic neuritis
  • Multiple sclerosis
  • Neuromyelitis optica
  • Myelin oligodendrocyte glycoprotein (MOG) antibody disorder
• Ischemic optic neuropathy
• Autoimmune disorders
  • Systemic lupus erythematosus 
  • Giant cell arteritis
  • Sarcoidosis
  • Behcet’s disease
• Infectious 
  • Viral
    • Herpes simplex1 and 2
    • Varicella-Zoster
    • Cytomegalovirus
    • Less frequent:
      • Human immunodeficiency, Epstein-Barr, Dengue fever, West Nile, Chikungunya
      • Measles, Mumps, Rubella, Influenza
  • Bacterial
    • Bartonella henselae (Cat-scratch disease)
    • Treponema pallidum (Syphilis)
    • Borrelia burgdorferi (Lyme disease)
    • Mycobacterium tuberculosis (Tuberculosis)
    • Less frequent:
      • Rickettsioses, Coxiella burnetti (Q fever), Tropheryma whippleii (Whipple disease)
      • Leptospira, Brucella, Mycobacterium leprae (Leprosy)
  • Fungal
    • Cryptococcus neoformans (Cryptococcus)
    • Candidiasis
    • Histoplasma capsulatum (Histoplasmosis)
    • Aspergillus fumigatus (Aspergillus)
    • Mucormycosis
  • Parasitic
    • Toxoplasma gondii (Toxoplasmosis)
    • Toxocara canis (Toxocariasis)
    • Diffuse unilateral subacute necrosis (DUSN)
• Drugs
  • Ethambutol/isoniazid
  • Chloramphenicol, sulfonamides
  • Amiodarone, digitalis
  • Quinine, chloroquine, hydroxychloroquine
  • Methotrexate, vincristine, tamoxifens
• Nutritional/toxic
  • Vitamin B deficiencies, particularly vitamin B12
  • Methanol/alcohol
  • Tobacco
• Compressive optic nerve lesions
  • Most often associated with a slow, subtle onset of signs and symptoms