Abstract
Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is typically associated with central nervous system inflammation and demyelination in younger populations; however, rare cases of isolated encephalitis in the elderly have been reported. This article presents the case of an 80-year-old male with mild cognitive impairment who developed progressive cognitive decline and a focal seizure. Despite negative imaging findings, elevated serum MOG antibody titers and pleocytosis in cerebrospinal fluid (CSF) analysis suggested MOG antibody encephalitis. Following treatment with intravenous immunoglobulin (IVIg), the patient showed significant cognitive improvement, and MOG antibody titers decreased, indicating a positive response. This case highlights the diverse clinical spectrum of MOGAD, demonstrating its potential to cause encephalitis in elderly individuals, even in the absence of typical imaging findings, and emphasizes the importance of promptly recognizing MOG antibody encephalitis to reduce associated mortality and morbidity.