Acute encephalopathy with biphasic seizures and reduced diffusion (AESD) is a syndrome of encephalopathy characterized by biphasic seizures. The etiology of AESD has been attributed to viral infection like influenza A and human herpes virus 6. AESD is the most common subtype of infectious pediatric encephalopathy in Japan, and is often observed in children with neurological problems, such as intellectual disability and motor delay. AESD is clinically characterized by a prolonged febrile seizure on day 1, followed by late seizures associated with deterioration of the consciousness level on days 4 to 6, and is radiologically characterized by delayed reduced diffusion in the frontal or frontoparietal subcortical white matter, the so-called bright tree appearance, on days 3 to 9. The exact pathogenesis of AESD is uncertain, however, excitotoxic injury with delayed (or apoptotic) neuronal death is hypothesized to be a possible mechanism.
