Gross postmortem examination showed widespread and severe signs of viral encephalitis: meningeal and perivascular inflammation, neuronophagy
, microglial nodules, endothelial damage, and severe brain edema.
At the time of autopsy, the gray and white matter demonstrated extensive destructive changes and infiltration of necrotic tissue by mononuclear inflammatory cells, perivascular lymphocytic cuffing, and clusters of microglia and macrophages marking areas of neuronophagy
. There was diffuse microglial hyperplasia, as well as severe gliosis with reactive gemistocytic astrocytes and microdeposits of calcium.
The microscopic neuropathologic changes among these autopsies consisted of a combination of necrosis that preferentially targeted neurons, degenerative changes of the glial and neuronal cells, white matter loss and axonal rarefaction, microcalcifications, microglial aggregates, gliosis, macrophage and mononuclear inflammatory cell infiltrates, neuronophagy
, and perivascular lymphocytic cuffing.