Three cases of atypical Rasmussen's encephalitis with delayed-onset seizures

We retrospectively analyzed the clinical characteristics of three ARE cases with delayed-onset seizures treated at Peking University First Hospital and Sanbo Brain Hospital from May 2021 to January 2023. We also reviewed previously reported atypical cases of Rasmussen's encephalitis (RE) in the literature, summarizing onset symptoms, seizure symptomatology, imaging findings, electroencephalogram (EEG) results, treatment course, and prognosis. The onset age of the three cases ranged from 1 year and 9 months to 7 years and 5 months. All three initially presented with limb motor disorders, which progressively worsened. Two cases developed focal seizures within 1 month of onset, whereas the third case had no seizures over 3 years. Brain MRIs revealed progressive unilateral hemispheric atrophy with multifocal abnormal signals, and PET-CT showed decreased metabolism in the affected hemisphere. EEGs exhibited asymmetric background rhythms with slow waves in the affected hemisphere. In the two children with seizures, epileptiform discharges from the affected hemisphere were recorded, including one case of sustained partial epilepsy. One child was initially diagnosed with autoimmune encephalitis, whereas two were suspected of having RE at onset. The two children with seizures were treated with immunotherapy and various antiseizure medications. Both underwent hemispherectomy because neither seizures nor limb motor disorders were effectively controlled. Post-surgery, neither experienced seizures during 2 years of follow-up, and both showed cognitive and motor improvements. The child without seizures received intermittent steroids and immunoglobulin therapy over 3 years. During 18 months of follow-up, the patient's motor function improved, and no seizures occurred. Seizures are common initial symptoms of RE. Such cases are often misdiagnosed or missed, leading to delays in optimal treatment. If symptoms are predominantly unilateral and EEG and imaging findings show laterality, the possibility of RE should be considered. Early diagnosis and treatment can reduce unnecessary investigations and improve prognosis. PLAIN LANGUAGE SUMMARY: Rasmussen's encephalitis (RE) is a rare disease that typically begins with seizures and generally has a poor prognosis. However, over the past 20 years, there have been reports of RE cases where the initial symptoms are not seizures. Our center has diagnosed and treated three such cases in the past 5 years. We aim to provide an overview of these atypical RE patients, focusing on clinical features, electroencephalographic (EEG) findings, and imaging characteristics to inspire early detection and diagnosis of RE, thus improving treatment timing and outcomes for RE patients.