Abstract
Atypical presentations of neuromyelitis optica spectrum disorder (NMOSD) continue to expand in pediatrics. NMOSD is mediated by pathogenic antibodies against aquaporin-4 (AQP4-IgG), a water channel protein found on astrocytes. NMOSD is distinct from multiple sclerosis in both its clinical course and treatment response. Our objective is early recognition for prevention of long-term neurological damage. We report a 14-year-old previously healthy girl who presented with subacute bilateral ptosis, diplopia, and vertical gaze palsy. Brain MRI revealed bilateral, nearly symmetric areas of T2 hyperintensity in the posteromedial thalami and periaqueductal region of the midbrain. Cerebrospinal fluid analysis was unremarkable; however, aquaporin-4 (AQP4) antibodies were detected in the cerebrospinal fluid (CSF) using a fluorescence-activated cell sorting (FACS) based assay at a titer of 1:128. She was treated with intravenous methylprednisolone and thiamine, followed by an oral steroid taper, with marked clinical improvement. This case highlights an atypical, brainstem-predominant presentation of NMOSD in a pediatric patient. It emphasizes the variability of NMOSD presentations in children and underscores the importance of early, comprehensive workup in patients with evolving neuro-ophthalmic symptoms. The purpose of this report is to raise clinical awareness of uncommon NMOSD presentations that may mimic other conditions and delay diagnosis.