A case report: Neuropsychiatric presentation of atypical Rasmussen's encephalitis.

Introduction: Rasmussen's encephalitis (RE) is a rare, progressive inflammatory neurological disorder characterized by treatment-resistant epilepsy, progressive hemiplegia, and cognitive decline. Although its pathogenesis remains incompletely understood, immune-mediated mechanisms are thought to play a central role. RE predominantly affects children, with only approximately 10% of cases occurring in adults. Diagnosis relies on the combination of clinical features, serial neuroimaging, and electroencephalographic findings. Early recognition is essential, as treatment options are limited and outcomes are improved with timely intervention. Atypical adult-onset presentations are particularly uncommon and may present significant diagnostic challenges. Patient presentation: We report a case that presented with atypical, adult-onset RE with major neurocognitive disorder. Management and outcome: The patient's diagnosis was made with neuroimaging 10 years following seizure onset. Findings indicated moderate generalised atrophy, with asymmetric involvement of the left cerebral hemisphere. Interventions required a multidisciplinary team, and pharmacological management included sodium valproate and lamotrigine for seizure control, as well as quetiapine and fluoxetine for behavioural disturbances. The patient's prognosis remains poor because of generalised brain atrophy limiting treatment options. Conclusion: There is a need to raise awareness of RE to assist with early detection and treatment. Late diagnosis may have contributed to the patient's poor prognosis. Contribution: Despite the need for further research, early neuroimaging of patients with new adult-onset seizures may help decrease morbidity associated with RE.