Diagnosis of neuromyelitis optica with bilateral vision loss as initial symptom secondary to acute middle encephalitis: a report of three cases.

Neuromyelitis optica (NMO) is an inflammatory demyelinating syndrome primarily characterized by optic neuritis and longitudinally extensive myelitis. However, the heterogeneity of neuromyelitis optica spectrum disorders (NMOSD) has expanded beyond the classical definition, revealing increased phenotypic diversity. Around 20-40% of NMOSD patients present with brainstem or hypothalamic involvement as their initial symptom. Case studies describing NMOSD with midbrain syndrome as the primary presentation are rare. This report details three cases where acute bilateral vision loss was the first symptom, followed by midbrain dysfunction, with a final diagnosis of NMOSD confirmed by serum AQP4 antibody testing or characteristic imaging findings.