Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD): a scoping review

Acute Encephalopathy with Biphasic Seizures and Late Reduced Diffusion (AESD) is a rare neurological disorder associated with infection, primarily diagnosed in Japanese children, characterized by biphasic seizures, restricted diffusion on magnetic resonance imaging (MRI), and neurological decline. We report an Italian case and provide a scoping review of cases published outside Japan in comparison with Japanese literature, using distinct sets of inclusion criteria as the reported incidence and quality of studies are different. Clinical and epidemiological characteristics are analyzed. Potential factors contributing to this unusual epidemiology are investigated. Our case (3-year-old girl) conforms to typical AESD features. AESD is very rarely reported outside Japan, where only 29 cases have been published (17 female, 2.6 ± 2.7 years). Their features closely resemble the Japanese patients. The only relevant difference is the infectious trigger distribution, with Human herpesvirus-6 (HHV6) predominantly reported in Japan (38.2%), but not in other areas. The morbidity of AESD extends beyond Japan, but it is probably underestimated with rare cases reported globally. Multicenter international studies are needed to clarify the AESD incidence around the world and their related genetic and environmental factors and to promote internationally shared diagnostic criteria and guidelines for acute encephalopathies including AESD.Impact AESD features are biphasic seizures, MRI restricted diffusion, and neuroregression. AESD is more common in Japan and very rare outside Japan. Clinical and instrumental features of AESD case diagnosed in Italy are reported. Review of Japanese and non-Japanese literature was performed. Genetics, underdiagnosis, underreporting, and environment may influence incidence.