Loss of myelinated axons and astrocytosis in an autopsy case of acute encephalopathy with biphasic seizures and late reduced diffusion.

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) is the most common pediatric encephalopathy in Japan, however, the exact neuropathology remains uncertain. The postmortem neuropathology in a patient with AESD revealed reduction of myelinated axons with early stage of astrocytosis in the absence of neuronal loss, which suggests the primary pathological damage in AESD involves myelinated axons and astrocytes rather than cortical neurons. An increased number of gemistocytic astrocytes at the corticomedullary junction may cause reduced diffusion, leading to the so-called bright tree appearance on magnetic resonance imaging, characteristic to AESD.