Causes of Bilateral Optic Neuritis
The primary causes of bilateral optic neuritis include multiple sclerosis, neuromyelitis optica spectrum disorders, myelin oligodendrocyte glycoprotein antibody-associated disease, systemic autoimmune conditions, infectious and inflammatory disorders, and paraneoplastic syndromes. 1, 2
Demyelinating Disorders
- Multiple sclerosis (MS) is a common cause of optic neuritis, though bilateral presentation is less common than unilateral involvement 1
- Neuromyelitis optica spectrum disorders (NMOSD) frequently present with bilateral optic neuritis, often with more severe vision loss and poorer recovery than MS-related optic neuritis 1, 2
- Bilateral simultaneous involvement is considered a red flag for atypical optic neuritis, often associated with NMOSD 2
- NMOSD is characterized by the presence of aquaporin-4 (AQP4) antibodies and typically affects both the optic nerves and spinal cord 1, 3
- Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) commonly presents with bilateral optic neuritis and is distinguished by the presence of MOG-IgG antibodies 4, 3
Autoimmune and Inflammatory Conditions
- Systemic lupus erythematosus can cause inflammatory optic neuritis, which may present bilaterally 1
- SLE-related optic neuritis is associated with poor visual outcomes, with only 30% of patients maintaining visual acuity greater than 20/25 1
- Common variable immunodeficiency has been associated with bilateral optic neuritis as an autoimmune manifestation 5
- Chronic relapsing inflammatory optic neuritis (CRION) can present with bilateral involvement and is characterized by steroid dependency 4, 3
Infectious Causes
- Infectious or post-infectious optic neuritis can occur bilaterally following viral infections 1, 4
- Measles (rubeola) can cause bilateral optic neuritis, particularly in unvaccinated individuals 1
- Epstein-Barr virus can cause follicular conjunctivitis and has been associated with optic neuritis 1
- Zika virus has been reported to cause bilateral non-purulent conjunctivitis and optic neuritis 1
Paraneoplastic Syndromes
- Paraneoplastic optic neuritis can present bilaterally in patients with underlying malignancies 6, 4
- This rare presentation should be considered in patients with cancer who develop rapid bilateral vision loss 6
- Antibodies against collapsin response-mediator protein 5 (CRMP5) can cause bilateral painless optic neuropathy, especially with optic disc edema 3
Imaging Characteristics
- MRI is the primary imaging modality for evaluating bilateral optic neuritis, with both orbital and brain MRI recommended 1
- Typical findings include T2 hyperintensity, optic nerve swelling, and contrast enhancement 2
- Coronal fat-suppressed T2-weighted sequences are optimal for visualizing optic nerve lesions 2
- Long optic nerve lesions are suggestive of NMOSD and MOGAD 2
- Posterior optic nerve involvement, including the chiasm, is suggestive of AQP4-IgG-seropositive NMOSD 2
Clinical Presentation
- Bilateral optic neuritis typically presents with painful visual loss, though it can be painless in some cases 1, 7
- Visual field defects, commonly central scotomas, and red-green color desaturation are characteristic symptoms 2, 7
- Photophobia is a common associated symptom 2
- Dyschromatopsia (color vision defects) is part of the classic triad of symptoms along with visual loss and periocular pain 7
- Contrast sensitivity, color vision, and visual field abnormalities may persist even after recovery of visual acuity 7
Diagnostic Approach
- Serum testing for AQP4-IgG and MOG-IgG antibodies should be performed in cases of bilateral optic neuritis 2, 3
- MRI of both orbits and brain with contrast is essential for diagnosis and to evaluate for associated demyelinating lesions 1
- Cerebrospinal fluid analysis may help differentiate between MS and NMOSD 1
- Evaluation for underlying systemic autoimmune diseases, infections, and malignancies is warranted in atypical presentations 4, 3
Bilateral optic neuritis represents a more concerning presentation than unilateral disease and requires prompt evaluation to identify the underlying cause, as treatment approaches and prognosis vary significantly based on etiology 3.