Case Report: Myelin oligodendrocyte glycoprotein antibody–associated cortical encephalitis masked by peri-ictal magnetic resonance imaging abnormalities

Abstract

One phenotype of cerebral cortical encephalitis in myelin oligodendrocyte glycoprotein (MOG) antibody–associated disease (MOGAD) is FLAMES (fluid-attenuated inversion recovery-hyperintense lesions in anti-MOG-associated encephalitis with seizures). FLAMES is characterized by its imaging features and epileptic seizures. We present a case in which these findings were masked by peri-ictal magnetic resonance imaging abnormalities (PMAs) associated with status epilepticus, making differentiation difficult. A middle-aged woman presenting with persistent right upper limb weakness and aphasia was admitted to our hospital. The patient was diagnosed with nonconvulsive status epilepticus based on electroencephalogram findings. Brain magnetic resonance imaging revealed findings consistent with typical PMAs. Although the seizures’ underlying etiology could not be identified initially, testing confirmed the presence of MOG immunoglobulin G in serum and cerebrospinal fluid, leading to a definitive diagnosis of FLAMES. FLAMES and PMAs share significant radiological overlap. Clinicians should maintain a high index of suspicion for MOGAD in middle-aged patients presenting with new-onset epilepsy of unknown origin, even when radiological findings appear to be typical PMAs.