ADULT-ONSET RASMUSSEN ENCEPHALITIS MIMICKING CHRONIC CEREBRAL INFARCT - A CASE REPORT.

Background: Rasmussen Encephalitis (RE) is a rare, chronic, immune-mediated inflammatory disease of the brain that results in progressive unilateral cerebral atrophy, severe neurological deterioration, and drug-resistant focal seizures. Although classically described in children, particularly those under the age of ten, a small but growing number of adult-onset cases have been documented in recent years, with a notable predominance among females. Neuroimaging plays a pivotal role in the diagnosis and differentiation of RE from other unilateral cerebral pathologies. Given the scarcity of imaging mimics and the significant therapeutic implications, it is essential that radiologists and clinicians recognize its characteristic imaging patterns to facilitate early and accurate diagnosis, thereby preventing delays in the initiation of appropriate treatment. Case Summary: We present a case of Rasmussen Encephalitis in an adult female, which was initially misdiagnosed as a chronic cerebral infarct on magnetic resonance imaging (MRI). A detailed review of subsequent imaging revealed typical features of RE, including progressive unilateral cortical atrophy and signal changes confined to one cerebral hemisphere. Conclusion: This case highlights the diagnostic challenge of adult-onset RE, which may mimic chronic vascular insults on imaging. Awareness of its distinctive radiological features and characteristic electroencephalogram (EEG) abnormalities are crucial for early and accurate diagnosis. Early recognition also allows for timely institution of appropriate therapy, which may slow disease progression, improve seizure management, and preserve neurological dysfunction.