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KembaraXtra-Emergency and Acute Medicine - Optic Neuritis
Description: Optic neuritis is an inflammatory disorder of the optic nerve resulting in demyelination and acute optic nerve dysfunction. It is strongly associated with multiple sclerosis and is the presenting manifestation in approximately 15–20% of patients with MS. Inflammation may involve the optic disc (papillitis) or the retrobulbar portion of the optic nerve, where the funduscopic examination may initially appear normal. The long-term risk of developing clinically definite MS depends on MRI findings, with significantly higher risk in patients demonstrating multiple demyelinating lesions.
Etiology and risk factors: Most cases are idiopathic and self-limited, but 20–50% are associated with multiple sclerosis. Other causes include postviral inflammation following infections such as varicella, measles, mononucleosis, HSV, or VZV, typically occurring weeks after illness. Granulomatous and infectious causes include tuberculosis, syphilis, sarcoidosis, cryptococcosis, Lyme disease, and HIV-related infections. Drug-induced optic neuritis has been reported with amiodarone, ethambutol, and tamoxifen. Genetic predisposition is suggested by associations with HLA-A23, B7, and DR2 alleles.
Clinical features: Patients typically present with subacute vision loss developing over days, peaking within 1–2 weeks, most often unilateral in adults and bilateral in children. Retrobulbar pain, worsened by eye movement, is characteristic. Color vision, contrast sensitivity, and depth perception are disproportionately affected compared with visual acuity. An afferent pupillary defect is common in unilateral cases. Visual field testing often reveals a central scotoma. Funduscopic examination may show optic disc swelling or appear normal. Uhthoff phenomenon, transient worsening of vision with heat or exertion, may occur.
Evaluation: A detailed history should assess age, sex, onset and progression of visual loss, eye pain, prior neurologic symptoms, recent infections, drug exposure, and family history of MS. Physical examination requires a complete ophthalmologic and neurologic assessment including visual acuity, pupillary reflexes, color vision testing, visual fields, and dilated fundus examination. Blood pressure should be assessed to exclude hypertensive optic neuropathy.
Diagnostic testing: MRI of the brain and orbits with gadolinium is the imaging modality of choice and demonstrates optic nerve enhancement in the majority of acute cases while also stratifying future MS risk. CT is less sensitive and primarily used to exclude compressive lesions. Laboratory evaluation is guided by clinical suspicion and may include CBC, ESR, syphilis serology, Lyme testing, ANA, HIV testing, and tuberculosis screening. Chest radiography may assist in evaluating sarcoidosis or tuberculosis. Formal automated visual field testing is recommended for baseline assessment and follow-up.
Management: Early ophthalmology and neurology consultation is essential. High-dose IV corticosteroids followed by an oral taper are recommended for patients with severe visual loss or those with two or more demyelinating lesions on MRI, as this shortens recovery time and reduces short-term risk of MS progression. Oral corticosteroids alone should be avoided, as they increase recurrence risk. Treatment decisions should be individualized in patients with fewer MRI lesions.
Disposition and follow-up: Admission is indicated for bilateral vision loss, diagnostic uncertainty, or when IV steroid therapy is required. Patients with unilateral involvement, stable condition, and reliable follow-up may be discharged with urgent neurology and ophthalmology review. High-risk patients should be referred for disease-modifying therapy consideration. Prompt follow-up is mandatory, as MRI findings are the strongest predictor of future multiple sclerosis.
Key points: Space-occupying lesions must be excluded before diagnosing optic neuritis. Acute bilateral visual loss with headache or diplopia raises concern for alternative emergencies such as pituitary apoplexy. MRI is critical for prognostication, and management should be coordinated with specialists to align with current standards of care.
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