Pediatric Post-COVID-19 Neuromyelitis Optica Spectrum Disorder: A Case Report.

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune astrocytopathy affecting the central nervous system, particularly the optic nerves and spinal cord. Post-infectious triggers, including SARS-CoV-2 (COVID-19), have been increasingly recognized as potential catalysts for this immune-mediated condition. We report the case of a nine-year-old boy who developed AQP4-IgG-positive NMOSD following confirmed SARS-CoV-2 infection. The patient's clinical onset began 1.5 months prior to admission with a seven-day episode of intractable vomiting, indicative of area postrema syndrome (APS). He subsequently presented with a 20-day history of progressive gait weakness, dysarthria, and complex ocular and cranial nerve deficits. Neurological examination revealed a right one-and-a-half syndrome, bilateral sixth cranial nerve paresis, left peripheral facial paresis, profound bulbar dysfunction (including a weak gag reflex and bilateral 12th nerve paresis), lower limb weakness (4/5), gait ataxia, and bilateral extensor plantar responses. Magnetic resonance imaging (MRI) demonstrated extensive central nervous system involvement. Brain MRI revealed typical hyperintense lesions in the periventricular white matter, thalamic-hypothalamic area, midbrain, medulla, and area postrema, alongside bilateral retrobulbar optic nerve enhancement. Spinal imaging confirmed longitudinally extensive transverse myelitis (LETM) spanning the C1-C6 and T2-T6 levels, featuring central gray matter involvement (H-sign) extending into the lateral columns. Cerebrospinal fluid was largely unremarkable. Serological testing confirmed the diagnosis with positive aquaporin-4 (AQP4)-IgG antibodies (cell-based assay (CBA)), positive antinuclear antibodies (ANAs) (1:80), and positive COVID-19 IgG antibodies, while anti-MOG antibodies were negative. Acute targeted immunotherapy was initiated with high-dose intravenous methylprednisolone (30 mg/kg/day for five days). While this achieved complete resolution of his gait abnormalities, visual impairment persisted. He subsequently underwent five sessions of therapeutic plasmapheresis as rescue therapy, resulting in full visual and neurological recovery. The patient was discharged on a maintenance regimen of oral azathioprine (2 mg/kg/day) and biannual intravenous rituximab. A four-month follow-up MRI confirmed dramatic radiologic improvement, with complete resolution of the spinal cord abnormalities. This pediatric case highlights post-COVID-19 NMOSD as a severe but highly treatable neurological emergency. It underscores the critical need for rapid diagnosis through detailed clinical recognition (including preceding APS), advanced radiographic imaging, and targeted serologic evaluation, as well as the efficacy of plasmapheresis for steroid-refractory symptoms to prevent irreversible disability.