P2.M244: Now you see me, now you don't: a toddler's tale of vision loss

Introduction: Complete vision loss in toddlers is a rare phenomenon, often attributable to a limited range of disorders. We present a case of acute disseminated encephalomyelitis in a toddler, where the primary manifestation was isolated visual loss attributable to optic neuritis.

Case Description: A previously healthy 20-month-old female presented to the emergency department with acute bilateral vision loss following recent symptoms of an upper respiratory tract infection. The child had spent the day with her grandmother, who noticed her bumping into objects. Upon arrival to the ED, she was afebrile with normal vital signs for her age. On examination, she was unable to fixate or follow objects, nor did she track movement or faces. Though she responded to voice, she did not blink to threat, hand waving, or light stimuli. Her pupils were equal and reactive to light, with intact extraocular movements. Apart from these findings, her neurological exam was unremarkable.

Laboratory evaluation was remarkable for elevated white blood cell count of 15800 cells/mm3 and erythrocyte sedimentation rate of 39 mm/h. A non-contrast computed tomography scan of the head revealed scattered areas of lower attenuation in the supratentorial white matter. A posterior ophthalmologic examination identified grade 2-3 bilateral disc edema with vessel tortuosity and dilated retinal veins. Subsequent magnetic resonance imaging of the brain revealed multifocal bilateral asymmetric intra-axial enhancing lesions, including bilateral 0405optic neuritis. Further comprehensive investigations, including a lumbar puncture and antibody testing, all returned negative. She was admitted to the pediatric intensive care unit and started on a prolonged corticosteroid taper for acute disseminated encephalomyelitis (ADEM) with significant improvement in her vision.

Discussion: ADEM represents an inflammatory demyelinating disorder of the central nervous system, often manifesting in childhood and characterized by symptoms such as ataxia, encephalopathy, vision changes, and extremity weakness. Despite its clinical presentation, the exact pathogenesis remains unknown, though autoimmune mechanisms are believed to be implicated. Environmental triggers, notably infectious agents, frequently precede its onset, with approximately 75% of cases reporting antecedent fever or infection. ADEM is a diagnosis of exclusion, with encephalopathy and characteristic brain MRI changes within the first 3 months serving as key diagnostic features. Classic MRI findings include diffuse, poorly demarcated and bilateral lesions, primarily in the cerebral white matter and spinal cord. Treatment strategies aim to reduce inflammation and immune dysregulation, using high-dose steroids, intravenous immunoglobulin, or therapeutic plasma exchange. Despite its acute presentation, the long-term prognosis for ADEM is generally favorable. Follow-up imaging three months post-treatment is recommended to preclude other demyelinating disorders and ensure optimal management.

Conclusion: Clinically isolated optic neuritis within the context of ADEM represents a rare occurrence. Recognizing the potential for long-term complications, timely recognition and treatment are crucial for restoring vision and optimizing patient outcomes.