Recurrent Myelin Oligodendrocyte Glycoprotein Antibody–Positive Aseptic Meningitis at the Identical Site in a Child: Leptomeningeal Enhancement Detected by Contrast-Enhanced FLAIR Imaging

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an acquired demyelinating syndrome of the central nervous system mediated by MOG antibodies. Clinical phenotypes include optic neuritis, transverse myelitis, and acute disseminated encephalomyelitis. MOG antibody-associated meningitis (MOGAM) is a form of aseptic meningitis characterized by the presence of serum MOG antibodies. Parenchymal lesions are typically absent in MOGAM; however, some cases may progress to MOGAD. Leptomeningeal lesions are rarely detected on contrast-enhanced T1-weighted magnetic resonance imaging (MRI) but may be conspicuous on contrast-enhanced fluid-attenuated inversion recovery (FLAIR) imaging. We report a case of a 5-year-old boy who initially presented with a prolonged headache and fever. Contrast-enhanced FLAIR imaging revealed localized leptomeningeal enhancement (LME), and the patient was treated for suspected aseptic meningitis. Subsequently, additional parenchymal lesions developed, and serum MOG antibodies were detected, leading to a diagnosis of MOGAD. He achieved remission with corticosteroid therapy but experienced a relapse a year later, with LME localized to the same site on MRI. At recurrence, the contrast-enhanced T1-weighted image showed faint leptomeningeal enhancement, whereas contrast-enhanced FLAIR imaging clearly depicted LME. Intravenous methylprednisolone pulse therapy was promptly initiated, which resulted in resolution without progression to MOGAD. This is the first pediatric report of recurrent MOGAM with LME recurring at the identical site. Contrast-enhanced FLAIR imaging enabled early detection of LME at recurrence and facilitated timely corticosteroid therapy, which may have prevented progression to MOGAD.